Bigfoot – automatic/remote stylophone control, Part 2

I was  constructing a device to play a modified stylophone remotely and automatically.  Using a 16 way analogue switch, the 24-pin 4067 chip, I designed a device where any one of 15 intervals on a 2-octave tonic sol-fa scale would be triggered by changing the chip’s 4-bit binary input.

First of all, I had used a physical control, a 16 position binary or hexadecimal rotary controller; what  I needed next to find was chips that could be made to output sequences of 4-bit binary numbers.

There are several of these, and I went for the 4516, which is a pre-settable binary counter.  It can, if left alone, repeatedly count upwards from 0 – 15, outputting numbers in binary form (’0 0 0 0′ to ’1 1 1 1′) on the pins marked ‘Q1′ to ‘Q4′ in the diagram below at the speed of a pulse connected to its clock input (Pin 15); or downwards from 15 – 0.  But by pre-setting a certain number, in binary form, on 4 extra binary inputs, marked ‘P1′ – ‘P4′ in the diagram, it can also be made to count upwards from this number to 15; or downwards from this number to 0.

This is how the 4516 is usually represented in circuits:

Q1 – Q4, as mentioned above, are the outputs, and P1 – P4 are the inputs for the number the count starts from, both in the form of a binary number.  The ‘Preset Enable’, pin 1, is usually held low (0v): when it’s taken high (+v) the number on the inputs P1 – P4 is loaded in and the next count starts from that number.  ’Preset Enable’ is sometimes referred to as ‘Load’ for this reason.  The ‘Carry Out’ is normally high, but goes low when the count ends.

The ability to count downwards from a set number would be useful for an arpeggiator, which could be set to repeat a sequence with a length of 2 – 16 notes, using the rotary encoder, described in Part 1, connected to the 4 binary inputs to preset the sequence length.

The circuit for this device was extremely simple, requiring only the rotary encoder, a momentary switch to tell the 4516 to load the sequence length number, an on/off switch and two inverters from a 40106 (which has 6 in it altogether) .  One of the inverters was connected as an oscillator, which was connected to the 4516′s Clock input: this determines the speed at which notes sound; the other inverter was connected between the ‘Carry Out’ and ‘Preset Enable’ pins: the ‘Carry Out’ is normally high, so the inverter keeps the ‘Preset Enable’ low; when the count ends the ’Carry Out’ goes low and the inverter sends a ‘high’ pulse to the Preset Enable, reloading the start number.

Pin 10 is connected to 0v in this circuit, which tells the 4516 to count down, not up: this was the easiest way to make sure it counted the right number of notes in the sequence.

In fact, counting up or down would result  only in a scale or part of a scale being played, so I made the output a bit more interesting by reversing the 4 outputs.  Instead of connecting the A output of the 4516 to the A input of the 4067, the B output to the B input, etc., I connected it so that A B C D were connected D C B A.  In essence this meant that consecutive notes in the sequence would not be consecutive notes in the scale, which I thought would be more interesting.

This produced method 2 of controlling the Stylophone: automatic arpeggiation.

*

The third method of controlling the Stylophone automatically used 3 more of the inverters in the 40106 which had been used for the 4516 clock and ‘Carry Out’ inverter.  The inverters were wired as oscillators.

This was the idea that came from the ‘Slacker Melody Generator’, described at http://electro-music.com/forum/viewtopic.php?t=27239&postorder=asc&start=50.  Each of the 4 oscillators is connected to one of the 4 inputs of the 4067; each runs at a different speed, changing the value on that input from low to high, or 0 to 1.  The different successive combinations of 0s and 1s produces a random melody, which can be changed by adjusting the speed of the oscillators, increasing or decreasing the rate at which each particular input changes from ’1′ to ’0′.

The reason the four oscillators have two capacitors each is simply because the original circuit I used suggested values of 220n; I soldered these in place, but the oscillators seemed to run too fast for my liking, and it was easier to add new ones in parallel than take the old ones out and replace them.  The result of putting capacitors in series is the opposite of putting resistors in series – instead of the overall value decreasing, it increases; the capacitance is larger and the oscillators run slower.

Having put the 4067 and the five DPDT switches in place, I then had to connect the relevant input/outputs to 24 different resistors, in a chain (or ladder) like the original one inside the stylophone.  I suppose it would have been possible to calculate the exact resistances, but I had some time ago obtained a hundred 10k presets for about 7p each, for exactly this kind of situation, so decided to use those and tune it by ear.

This took some time, but at the end of it I had a substitute resistor chain for the SoftPot Stylophone and some methods of controlling it automatically.

*

It then occurred to me that with this arrangement, all this extravagance could only control one stylophone at a time, so I had a think about how to connect more instruments (and possibly instruments other than stylophones!).

The way to do it, it seemed to me, was to use the binary inputs to the 4067 as an output: any device could then be controlled, just by installing the 4067 and the five ‘major/minor’ switches in it – or perhaps some other suitable arrangement.

So I added two 5-pin DIN sockets as outputs, the five terminals being A, B, C, D and 0v.  Each of the four A, B, C, D outputs was buffered, using four of the six buffers in a 4050.  The 4050 is similar to its sister chip, the more well-known 4049; but whereas the 4049 inverts its outputs, the 4050 doesn’t.  This chip has even cleverer properties, which I will be using in a later project, but here I used it to ensure the binary outputs were of sufficient strength to make their way through a connecting cable and satisfactorily operate external circuitry.

I also added at this stage Clock In and Clock Out sockets, which would enable Bigfoot to set the tempo of a piece involving different instruments, or follow the tempo set elsewhere.  These two input/outputs passed through the remaining two buffers on the 4050.

The final thing was to add two more 5-pin DIN sockets, this time as inputs.  This would enable external circuitry to control the 4067s.  I had several more ideas of suitable external devices which could be used to do this, and I hope to be able to get around to making these quite soon.

The only other unusual component needed to get all this to work was a suitable master switch, to select the various external and internal inputs to the 4067s.  This had to have 4 poles – the A, B, C, D binary inputs – and 5 positions.  4 pole, 3 way rotary switches are easy to come by, but 4 pole, 4 or 5 way are not.  Fortunately, I was able to source a 4 pole, 5 way switch on eBay from a supplier in Hong Kong for just a couple of quid, so everything was in place.

With a circuit like this – just a handful of chips and a few external components – you either get a neatly laid out PCB or a rats’ nest of wiring.  I ended up with a rats’ nest of wiring . . . however, it worked, even when crammed into the case, with the addition of an extra section underneath the ‘big foot’ I had selected.

This picture shows the two binary input sockets on the left.  The 5 way switch is the knob on the front of the Bigfoot, just the right of centre in this picture.

Due to a certain amount of experimentation along the way, some changes of mind about the functions, and some difficulties in getting all the switches and sockets to fit, there were some extraneous holes which I had drilled in the case.  The plastic frogs are there to hide the holes.  I also added a square of velcro on the back where I could attach a battery holder, as I had done with a number of previous projects.

Bigfoot – automatic/remote stylophone control, Part 1

I’d made enough instruments for the time being, and it was time to construct some automatic controllers – sequencers, arpeggiators and the like – as an alternative to playing them by hand.

When I made the SoftPot Stylophone, I had added a socket which allowed external circuitry to replace the chain of resistors which govern the pitch of the instrument.  This project was to make a device which would be able to use this feature to operate the SoftPot Stylophone remotely, and this rather blurry photograph shows the result – Bigfoot:

I got the inspiration from several places: the arpeggiator and sequencer from Fun with Sea-Moss: http://milkcrate.com.au/_other/sea-moss/; the melodygenerator by Slacker described on the electro-music.com forum: http://electro-music.com/forum/viewtopic.php?t=27239&postorder=asc&start=50; and the Intro to Lunetta Synths at https://docs.google.com/document/edit?id=1V9qerry_PsXTZqt_UDx7C-wcuMe_6_gyy6M_MyAgQoA&pli=1,  All these sites are full of great ideas and practical examples.

The main chip used in the circuits described above is a 4051, which is basically a single-pole 8-way switch.  It’s usually depicted in circuits like this:

The way it works is like this: it’s an analogue switch, not a digital switch, meaning you can connect anything you like to the pole (pin 3, marked Z in the diagram) and the 8 switch input/outputs (on the right-hand side, marked Y0 – Y7).  It doesn’t have to be logic high or logic low (i.e. +v or 0v) , it can be any voltage, an audio signal, anything – just like a physical switch.  Any one of the 8 input/outputs can be connected – one at a time – to the pole, not by turning a physical switch, but by the logic high or logic low status of the 3 ‘Select’ inputs (pins 9, 10 and 11, marked S1 – S3).

You can have every combination of logic high and logic low on the three Select inputs, ranging from 0v on all of them, 0v on one of the three and +v on two of them, +v on two of them and 0v on one, or +v on all of them.   There are eight possible variations, starting with 0v on all of them, which you could represent as ’0 0 0′ or the binary equivalent of the number zero, to +v on all them, which could be represented as ’1 1 1′ or the binary equivalent of the number 7.

If you feed 0v to all three of the Select inputs, or ’0 0 0′, this is lowest possible binary number, so the lowest or first input/output is connected to the pole (Y0, pin 13); if you connect, say the one on pin 9 (S3) to +v and the other two to 0v, this would be the binary number ’1 0 0′, the equivalent of the number 4.  Because the sequence starts with ’0 0 0′ , or zero, feeding in ’1 0 0′  connects the 5th rather than 4th input/output to the pole (Y4, pin 1).  By connecting all the Select inputs to +v, or ’1 1 1′ (the number 7), the 8th input/output is connected to the pole (Y7, pin 4).

In the circuits I looked at, a common type of connection would be to have the pole connected to the part of an oscillator circuit that determines the pitch, and 8 input/outputs connected to different value resistors.  This would mean that a different resistance would be connected to the oscillator and a different pitch would be sounded when each of the 8 input/outputs was connected to the pole.

You could determine whether each of the Select inputs was a ’1′ or a ’0′  with  three 2 way switches, +v one way, 0v the other way, and change the notes by moving different switches up and down.  But this would be rather tedious.  By adding a circuit that automatically changed the ’1′s and ’0′s, you have a melody generator, arpeggiator or sequencer.

This was the kind of circuit I was after.

However, 8 notes was bit restricted.  Not restricted because there are 12 notes in one octave, though: I reasoned that you could make life easier for yourself by only allowing notes in a single scale – the ‘do’, ‘re’, ‘mi’ approach so succinctly captured in the Rodgers and Hammerstein song from The Sound of Music (‘Do a deer, a female deer/Re, a drop of golden sun’, etc.).  There are only 8 notes in a  ‘do’, ‘re’, ‘mi’ scale, including the next ‘doh’ up from the one you started from.  If you just use those, you’ll never get an ‘out of tune’ note in your arpeggio or sequence.

The proper name for the ‘do’, ‘re’, ‘mi’ system, by the way, is ‘tonic sol-fa’, and was invented here in East Anglia by Sarah Ann Glover of Norwich, who lived from 1785 to 1867.  This 1868 woodcut shows Sarah Ann teaching ‘do’, ‘re’, ‘mi’ to the musical children of Norfolk:

(Why this public domain picture  is held by Music Department of the Bibliothèque National de France is not adequately explained by the Wikipedia, where I found it.  I suppose the fame of ‘do’, ‘re’, ‘mi’ is international).

No, it was restricted instead because the SoftPot Stylophone has 12 ‘do’, ‘re’, ‘mi’ steps from the bottom of the keyboard to the top – and in any case could be made to produce notes outside the range of the built-in keyboard.

So I decided I needed 16 steps (2 octaves, including ‘do’ two octaves up from the start), and found a chip, the 4067, to do the job.  The 4067 is a single-pole switch like the 4051, but with 16 switches instead of 8.  The only way it differs in operation from the 4051 is that it requires 4 Select inputs in order to go all the way from ’0 0 0 0′ (zero, meaning the first input/output is connected) to ’1 1 1 1′ (15, meaning the 16th input/output is connected).

The 4067 usually appears in circuits like this:

It’s very similar to the 4051: there’s a Pole (pin 1, marked Z); 16, instead of 8, input/outputs (right-hand side, marked Y0 – Y15); and 4, instead of 3, Select inputs (pins 10. 11, 13 and 14, marked S0 – S3).

I also decided to make things slightly more complicated by considering alternative scales.  If you follow the ‘do’, ‘re’, ‘mi’ scale of the Rogers and Hammerstein song, this is a major scale.  If, on the other hand, you wanted to play, for example, a minor scale, you would find that ‘mi’, sometimes ‘la’ and sometimes ‘ti’ have to be changed to be a semitone lower.  And occasionally you might feel like making ‘re’ and ‘so’ lower as well.  (‘Do’ and ‘fa’ can be left alone!).

I’ll explain in a minute exactly what scales I had in mind when doing this, and where I got the idea from, but adding the ability to sharpen or flatten certain notes of  the scale meant that I needed 25 notes instead of 15, so the 4067 was wired up like this:

The notes depicted are the notes that would be used in the key of A.  Since the SoftPot Stylophone has a tuning control (in fact two tuning controls!) on it, it can be made to play in any key, not just A; the circuit here doesn’t need to be changed, only the tuning on the SoftPot Stylophone itself.

Each of the 16 outputs of the 4067 is connected to a resistor in a chain.  The top of the chain is connected to the tip of a 3 way (‘stereo’) 3.5mm socket; the bottom of the chain is connected the ring, and the sleeve is connected to pin 1 of the 4067 – the pole of the 16-way switch.  When plugged in, it takes the place of the Stylophone’s own resistor chain.

Note that switches allow you to choose between 1) major and minor 2nd (‘re’); 2) major and minor 3rd (‘mi’); 3) major and minor 5th (‘so’); 4) major and minor 6th (‘la’); and 5) major and minor 7th (‘ti’), as you see fit.  C1/C#1 and C2/C#2, D#1/E1 and D#2/E2 etc. use the same switch, so there are 5 of these switches, not 10.

The reason I chose to do it this way is because of an extremely interesting article – series of articles, actually – which I read on The Tonal Centre website, written by Andrew Milne.  I’m not in the slightest bit concerned that the theory described there is ‘unconventional and some of the concepts . . . quite novel’, as it seems to me to make perfect sense, and presents a coherent view of scales and chords which I’ve found quite easy to understand, and useful to use.  Furthermore, Milne’s motives for writing the articles are ones with which I would hope none of my readers could disagree: ‘not for theory to be an intellectual straight-jacket which smothers spontaneity, but as a springboard for creativity and, even more importantly, as a foundation for exploration’.

Essentially, the articles do precisely as the author says in his introduction: ‘convince you that there is a lot more for the tonal composer to experiment with . . . than just the major and the minor scale.’

I can’t explain everything in the articles because a) there is too much, and b) I don’t understand it all; but essentially, the points I want to draw attention to are these:

1. What constitutes a useful and versatile scale?

A scale should constitute ‘a unified collection of notes – a selection which is in some sense complete and to which any addition is heard to be extraneous’.

2.  What makes a scale useful as a melodic resource?

A scale should be ‘reasonably smooth and even, without sudden gaps which sound as if a note has been omitted, or sudden concentrations of notes which sound as if an extraneous note has been added’.

3.  What makes a scale useful as a harmonic resource?

Because three-note major and minor chords are the basis of our kind of western music (like C-E-G and C-Eb-G), a scale shouldn’t have any notes which aren’t part of a three-note major or minor chord.

Of all possible scales there are only five prime scales which satisfy Milne’s criteria, as above. (These are the main criteria, but see the full article for a couple of others).

All of these scales contain, as it happens, seven notes, and these are clearly the most useful and versatile scales to use.  This was good news for me, as the Bigfoot would inevitably use 7-note scales.

There are 8 different scales altogether in Milne’s system, not just 5, because of  differences between major and minor, and so on, and these 8 variations of the 5 ‘prime scales’ (in the key of C) are:

1.  The diatonic scale, major and ‘aeolian’:

C-D-E-F-G-A-B

C-D-Eb-F-G-Ab-Bb

2.  The harmonic minor scale:

C-D-Eb-F-G-Ab-B

3. The harmonic major scale:

C-D-E-F-G-Ab-B

4.  The melodic scale, major and minor:

C-D-E-F-G-Ab-Bb

C-D-Eb-F-G-A-B

5.  The double harmonic scale, major and minor:

C-Db-E-F-G-Ab-B

C-D-Eb-F#-G-Ab-B

So, there are 8 different scales you can use, which all allow you to make interesting melodies and chords.  Each one has its own ‘character’, and some are much more commonly used than others.

This series of articles seemed to me when I came across it to be an extremely good guide to useful scales, and could be a help to anyone: you could use the description above to work out what scale or scales you commonly use, and then try writing a composition or improvising a solo using a completely different one.  There’s bound to be at least one you’ve never thought of using before!

Bigfoot allows the 2nd, 3rd, 5th, 6th and 7th (D, E, G, A, B in the above examples) to be individually adjusted, so arpeggios and sequences in all – well, almost all! – of these scales are possible.  The double harmonic minor isn’t possible because Bigfoot can’t produce F# and G at the same time; but 7 out of 8 isn’t bad!

So, 16 individual intervals are available  from the Bigfoot, spread over two octaves; the tonic is repeated 3 times, at 3 octaves; the 4th is repeated twice, at two different octaves; the other 10 notes are switchable between a ‘normal’ or ‘flattened’ version, which is semitone lower.

Hang on, that’s only 15 intervals . . . Well, since all 16 Select input combinations from ’0 0 0 0′ to ’1 1 1 1′ could be used to produce notes, there might in some circumstances be no way of stopping the Stylophone from sounding; so what I did was to start with ’0 0 0 1′ (the second output) and make that the lowest note, reserving ’0 0 0 0′ (the first output) for a rest where no note would sound.  I added a switch so that the first and second inputs could be connected together for those situations when this would be better.

I also added a START/STOP switch, which is what pin 15 of the 4067 does: if connected to +v it stops, and all the switches are disconnected, regardless of the state of the Select inputs; if pin 15 is connected to 0v the switches start to work.  (The 4051 also has this feature).

In practice, I actually installed a second 4067, with the two 4067′s being connected only at the 4 Select inputs (pins 10, 11, 13 and 14).  I wanted to have an LED indication of which switch was connected, and had to separate this function from the resistor chain that produced the notes.

So the pole pin of the second 4067 was connected to +9v via two 1k resistors [not one, as shown in the diagram], and each of the 16 outputs was connected to a green LED (matching the green case the circuit was built into).

In order to test the LEDs – and later to test the notes which were being produced – I needed some way of connecting exactly the right input/output to the pole of the switch, so I would know I was adjusting the right preset.  This meant feeding exactly the right combination of  +v (’1′s) and 0v (’0′s) to the Select inputs, to get exactly the right output.

I considered four 2-way switches, +v one way, 0v the other way, and changing the notes by moving different switches up and down, as I described before – but it turns out there is a device which does this job very simply, just like turning a rotary switch: a 4 bit binary (sometimes called hex) rotary encoder.  I wouldn’t say these are extremely easy to come by, but this is the one I got:  http://uk.mouser.com/ProductDetail/Alpha-Taiwan/RE2001F-40E2-20F-4B/?qs=yA6kp8fx8Y4fjZ7sDt2l6A%3d%3d.

(The above picture shows a typical rotary encoder made by Alpha Electronics.  RS online sell a couple, but looking at the product details, I don’t think the connections of the ‘Code 033′ version they sell is right.  There are lots of 2 bit encoders, and lots of encoders which are not binary or hex.  They won’t work – it has to be 4 bit binary with 16 positions, starting with ’0 0 0 0′ at position 1 and stepping through the binary numbers 1 – 15, ending up at ’1 1 1 1′ at position 16. These are referred to as ‘hex’ because the hexadecimal system has 16 numbers in it [usually written as '0 1 2 3 4 5 6 7 8 9 A B C D E F' - a more user-friendly way of depicting '0 0 0 0' to '1 1 1 1']).

I needed to use the encoder for another part of the circuit, which I’ll come to later, but for the time being its 4 outputs were connected directly to the 4 Select inputs, ‘A B C D’, of the 4067s.  Its other connection, ‘Common’, was connected to + volts.  To test it, I used  4 LEDs, and could see that turning it from position 1 to position 16, it automatically output the binary numbers in order from ’0 0 0 0′ to ’1 1 1 1′.

It’s worth mentioning an important point, to avoid later confusion, which is that ‘D’ is actually the bit on the left in a binary number such as ’1 1 0 0′, and ‘A’ is the bit on the right.  You might sometimes see ‘D’ referred to as the ‘Most Significant Bit’ (or ‘MSB’) and ‘A’ as the ‘Least Significant Bit’ (‘LSB’).  That means the number sequence goes like this:

D  C  B  A

0  0  0  0

0  0  0  1

0  0  1  0

0  0  1  1

0  1  0  0

etc.

The other thing about rotary encoders is that they don’t usually have a stop, they just go round and round.  This is fairly useless if you need to know where ’1′ is, or where ’16′ is, and this is the main reason why I decided to incorporate the LEDs as a visual indication.  The other reason is that sequencers and so forth really ought to have flashing lights on them.

The rotary encoder is the knob on the right-hand side of the Bigfoot, just to the right of centre in this picture:

I glued the LEDs in place on the top and connected up the rotary switch.  Sure enough, with each turn the LEDs lit up one by one, one at a time, and now it was possible to tell which was position 1, which was position 2, etc.

Not only that, with the lack of a stop at 1 and 16 – which you would expect with a normal rotary switch – if nothing else I had Method 1 of controlling the Stylophone remotely: a manual method of arpeggiation by spinning the encoder backwards and forwards! . . .

. . . Entertaining, but not the automatic method I was looking for, however, so I moved on to Part 2 of the construction.

BigBoy BeatBox

You’ve got a Stylophone, you’ve got a Stylophone Beatbox – but don’t you sometimes wish the two could be combined into one instrument? . . .

Well, now that wish has become reality, with the ‘BigBoy BeatBox’: two great Stylophone products in one!

As the picture suggests, the BigBoy BeatBox is, in fact, two great Stylophone products literally glued and bolted together, with some of their internal circuitry combined.  The way it was created was like this:

1.  The Stylophone

The Stylophone half of the instrument is, in fact, a recreation of the original ‘Big Boy’ – a regular Stylophone S1 inside a Beatbox case.  As mentioned in an edit to the original post here, I managed to inflict terminal damage on the ‘Big Boy’ by reckless experimentation.  I normally do this before finishing an instrument, this time I contrived to do it afterwards . . . so the first thing I had to do was remove and replace the electronics with a new donor Stylophone I had lying around.

The actual process closely followed the construction of the original, but was made easier because of the sockets and wiring still remaining in the Beatbox case.  First of all, the end had to be sawn off the Stylophone circuit board, which is too long to fit in a Beatbox case; then the lowest 12 notes of the keyboard were connected to the 12 outside pads of the round Beatbox keyboard.  Fortunately, the wires attached to the Beatbox keyboard remained in the case, and just needed connecting to the appropriate Stylophone keys.  The Beatbox’s amp circuit board was taken out, but the Stylophone’s was kept and connected to the Beatbox’s speaker.  A power socket was connected to the Beatbox’s on/off switch, and the Stylophone’s on/off and vibrato switch circuit board disconnected.

I decided to replace the ‘Big Boy’s troublesome original 3-way octave switch with a simple  pitch potentiometer.  I used a 100k for  coarse tuning, in series with a 10k for fine tuning and a 100k variable preset to fix the highest pitch available.  Previous experimentation with Stylophones had taught me they have no objection to going down to very low pitches, but they cease to function – usually temporarily – if the pitch is taken up too high: on resetting, when this happens – by switching the power off and on – sometimes they will begin to work again, sometimes they won’t.

That’s what I did to the original ‘Big Boy’, and there’s no cure apart from throwing the circuit board away and starting again.  The likelihood of this happening is increased because I don’t just replace the tuning potentiometer pin-for-pin – the range of voltages available between the two pins the Stylophone uses isn’t wide enough for very large pitch variations, so I use only one of the pins that the original tuning potentiometer was connected to – the left-hand one – but connect the other one to +v.

The two new pitch controls were fixed to the front (the rounded end) of the Beatbox case, as was a replacement 10k log volume control.  The problem with the Stylophone’s original volume control was not that it wouldn’t work perfectly well, but that it would have had to be on the side of the case which I was intending to fix permanently to  the other Beatbox.

The original ‘Big Boy’ had no vibrato, but I decided the recreation should have a variable control, as fitted to the ‘Alien’, my first Stylophone modification project.  All this involved was connecting a 1M potentiometer instead of an on/of switch between the two vibrato connections next to the power connection on the main Stylophone circuit board.

Apart from an output socket and a switch to cut out the internal speaker, that half of the BigBoy BeatBox was done.

2.  The Beatbox

The other half of the instrument was a plain beatbox, with very little in the way of modifications.

The first thing I did to it was to replace the tuning potentiometer with a larger one of 100k (a direct pin-for-pin replacement this time), allowing for considerable slowing down and lowering of the pitch of the drums and other sounds.

I also followed an excellent example in this YouTube video: http://www.youtube.com/watch?v=xXdelnxXF7A to add buttons in parallel with the ‘Record’ and ‘Play’ pads normally operated by the stylus.  The trouble with the stylus-operated method is the delay in time between activating ‘Record’ with the stylus, and then using the same stylus to stop recording and begin playing the pattern you want to  be looped, as the loop begins the moment ‘Rec’ is selected.  With a small normally-open tactile switch as an alternative method of beginning and ending the recording period, you can be much more accurate as regards timing.

It’s worth mentioning at this point that, like the original Stylophone itself, the Beatbox comes in more than one variety, as far as circuitry is concerned.  I noticed two significant variations between the Beatbox I used in my ‘test to destruction’ phase, and the one that eventually found its way into the finished instrument: in one case, there was a tap from the battery compartment at 3v, which fed into the circuit (via the 3-way tone control) as well as the full 4.5v; and the layout of the circuit board was different.  As it happens, spots on the board marked ‘Rec’ and ‘Play’ were easily accessed in one case – the test unit – but not in the other – the one I was eventually to use.

In my experience, the Beatbox is a very delicate circuit, and it doesn’t take much to do something to it that will cause Record or Play to malfunction, or the output quality of the sound samples to degrade; so, proceed with caution, I’d say.

A third new button I added to this unit was ‘Reset’.  The Beatbox’s method of erasing an old loop and re-recording a new one is to switch the power off and on again.  The original power switch had to be removed as it was on the side of the case which was going to be fixed to the other Beatbox case – and there would, anyway, be a single power switch for both units: so the third button is a direct replacement for the Beatbox power switch, but now a normally-on, push-to-break, supplying power to the Beatbox side only.  To reset and re-record just takes a quick press and release of this button.

Finally, a new 10k log output volume pot was fixed to the front of the unit.

3  Joining the two halves

Superglue and two bolts was all that was required to physically join the two Beatbox cases, plus a couple of holes through which wires could pass from one side to the other.

The easiest way to connect the power seemed to be to detach the +v and 0v wires from the battery compartment on the Beatbox side and attach these to the original ‘Big Boy’ Stylophone side, which had a power input socket.

In the end I decided that whereas the battery compartment of the Big Boy Stylophone had to be removed – there was no room for batteries as well as the Stylophone circuitry – the one in the Beatbox could be used.  So I wired in a power cable which ran out of the back and was just long enough to reach the power socket in the other half.  In this way the instrument could be powered from an external source, or from internal batteries, and there was no need for a switch to change from one to the other.

The two 10k volume controls were taken to two individual tone controls.  I just wanted something fairly rudimentary, so I used a circuit from http://www.muzique.com/lab/swtc.htm called the ‘Stupidly Wonderful Tone Control’.  The component values I used were quite different – and I have no idea why – but the format of the circuit was more or less the same, and gave a little bit of variation to the tone.

After the tone controls, the two outputs were joined with 10k resistors to the original Beatbox volume control, and then the ‘Big Boy’ Stylophone amp circuit board.  This meant that the sound from both units was going to the ‘Big Boy’ half , and the volume and tone of each unit could be independently varied.  The input to the Beatbox amplifier was disconnected, and the speaker removed.

Now I had an instrument in a single conjoined case, with a single power supply and output through a single speaker or output socket.  There were two styluses and two keyboards, and – as I had hoped, but not expected with any confidence – both styluses work on both keyboards!  This means that both units can be played with a stylus in each hand, and quicker and more rhythmic patterns can be played.  I extended the wires to the styluses slightly to make sure they could reach right across both keyboards.

When using two styluses on the ‘Stylophone’ side of the unit, the ‘Beatbox’ side needs to be set to ‘Play’, otherwise that stylus will only work for a very short period and then not sound any more.  I haven’t timed the ‘very short period’, which might give a clue, but this is probably to do with the circuitry which regulates the maximum of 8 seconds (at ‘normal’ tempo) for which the Beatbox can record.

The complete circuit looks something like this:

The following pictures show the inside of the instrument shortly before it was finished:

This is the ‘Big Boy’ stylophone half.

1 = speaker cutout switch

2 = socket for external 4.5v power source

3 = 3.5mm sound output socket

4 = Stylophone S1 circuit board with permanently soldered connections to first 12 keys

5 = socket for extra stylus, remaining from original ‘Big Boy’ design – not really needed now

6 = fine tune pitch control

7 = variable preset to prevent the Stylophone’s highest note from being too high and causing the circuit to malfunction

8 = coarse pitch control

9 = Stylophone volume control

This the Beatbox half.

1 = the original Beatbox output and ‘mp3′ input sockets, no longer used

2 = Stylophone tone control

3 = Beatbox tone control

4 = Original Beatbox volume control, now master volume

5 = ‘Reset’, push to break switch

6 = wires going to ‘Play’ and ‘Record’ push to make switches mounted on top surface of Beatbox

7 = original Beatbox tempo switch, still in-circuit, but no longer used

8 = Beatbox pitch control

9 = Beatbox volume control

The features visible on the outside were these:

Before finishing I gave the speaker grilles a coat of blackboard paint.  The reason I used blackboard paint was a) it was the only black paint I found in my garage not in a spray can, and 2) it gives a pleasing matt finish, but is more durable than water-based matt emulsion.

The rear of the instrument was sprayed black and the holes masked with painted material.

The UFO and the Shuttlecraft

The UFO is a simple device for controlling instruments with light-dependent resistor (LDR) controls, for example the Opto-Theremin described in an earlier post.

It started life as one of those battery-operated lights where you push on the top to switch it on and off:

I painted it silver, and added bits to make it more flying saucer-like, some LEDs that change colour slowly, and a 5-LED goose-neck lamp that I found in a local Poundshop.

The colour-change LEDs have no important function, but the brightness of the goose-neck lamp can be controlled with a potentiometer, and can thus be pointed at an LDR and used to vary – in the case of the Opto-Theremin – volume, pitch or filter cut-off frequency.  Here you can see the lamp and the potentiometer: I didn’t attach a knob as I couldn’t find one that looked more UFO-like than the knurled shaft:

The goose-neck lamp is meant to operate from a computer USB port, so plugs into a USB socket, with only pins 1 and 4 (5v and 0v) connected.  The battery holder in the lamp is designed for 6v, and therefore had space for 4 AA batteries, but I mostly use 9v, so I adapted it to take a PP3.  I restricted the potentiometer from putting the full 9v through the LEDs, in case it was too much for them.

The maximum voltage allowed for the color-change LEDs was 4.5v; there are 4 of them, so I connected two in series on one side of the dome, in parallel with two in  series on the other side.

I also added some extra 3.5mm mono sockets, as can be seen in the picture, as this is a system I use for distributing power.  When the Opto-Theremin is used in conjunction with the UFO, it can receive its power from there, rather than from a separate battery.

This picture shows the two being used together:

These pictures illustrates the soothing effect of the constantly changing colors:

The ‘Shuttlecraft’ isn’t really an invention of my own: in fact, it’s just a multi-LED lamp on a headband, as worn by cyclists.  It appears here only because it’s an aid to playing the Opto-Theremin.  Because light levels are often too low to get the maximum variation in parameters controlled by LDRs, it can be useful to have extra light to hand: but when your hands are occupied playing the instrument, the next best place is on your forehead.

Although the UFO and the Shuttlecraft were created with the Opto-Theremin in mind, they could be used with any instrument (or effect) that uses an LDR – for example, my first Stylophone mod, the ‘Alien’, or the Stylophone 350S.

Theremin 2 – The Opto-Theremin

In my previous post Theremin 1, I described an optical theremin circuit which was ultra-simple – and worked!  However, I described how once I had finished it and played with it for a while, I realised there were some slight problems in being able to play it effectively; and also began to wonder how I could make it sound more interesting and varied.

This post describes what I did to finish it off.

The solution I came up with to make it sound more interesting was based on something I’d seen on a couple of Lunetta-related websites: a 4040 divider outputting several octaves at once, which could be individually selected and mixed together to create the final waveform.

This was the original optical theremin circuit:

I reduced the value of the timing capacitor in the original circuit from 22n to 15n to make the basic pitch a little higher and connected the 4040 between the output of the oscillator – pin 2 of the 4049 – and LDR2.  Together with the direct output from the oscillator, I used the first 7 outputs from the 4040, covering 8 octaves overall – a rather excessive range, but the pitch variation obtained using LDR1 was very wide, and I figured the highest and lowest notes might be needed at some point – contributing to the tone, even if not the main pitch.

The 8 different octave outputs were connected together via SPST switches, and various combinations of octaves did produce a surprising variety of tones.

Just one more thing was needed, I thought, to maximise the availability of square waves at 8 octaves, and that was a filter.  I’ve written elsewhere in the blog about Ray Wilson’s simple-but-effective 741-based low-pass filter from the Music From Outer Space website, which I liked so much I built two of them: one of them as a stand-alone unit (Active low-pass filter); and the other one here in the Optical Theremin.  The only difference was that in this case I replaced the cut-off frequency control with another LDR (LDR3).

I discovered afterwards that I hadn’t used the most up-to-date version of the circuit, but adding the extra cut-off frequency fine adjustment and resonance control (the extra features of the revised version) would have been too much.  As it was, I already had 3 LDRs, and only two hands to operate them with.  I added switches to select between the two volume and filter LDRs and two potentiometers, which would enable one of them to remain constant while the other one was manually controlled.

The filter circuit went between the outputs from the 4040 and the input to the Volume LDR (LDR2).  And that was it for the design and construction of the circuit, which now looked like this:

The reason for passing the output of the 4049 oscillator (at pin 2) through two more stages (spare ones in the same 4049) was to give it the same power as the outputs from the 4040.  Using the signal from pin 2 as an output as well as feeding the input of the 4040 seemed to be too much for it, and it wouldn’t work.

Also – as I had done with a couple of recent instruments (for example, the Cracklephone) – I added a pair of banana sockets, so a larger external speaker could be used.  Not shown in the diagram is a switch to cut out the internal speaker when these sockets are in use; and a similar arrangement to the Cracklephone, two 3.5mm sockets where a small goose-neck microphone can be attached.  This is not part of the Theremin circuit, and is the nearest it gets to having a line-out.

This what the inside of the case looked like just before I put it back together.  I don’t recommend you try and stuff so much inside a small case, as I always seem to be doing.

As for the physical construction of the instrument this presented one or two problems.

The one of most interest concerns the LDRs.  Electrically, these seemed to work perfectly; but the problem with them is they’re so small, and it’s very difficult to make subtle changes to the amount of light falling on them with a large human hand.

This is a perennial problem with these small-sized LDRs, and what I decided I needed was something like a torch or spotlight has to widen the spread of light – a dish or reflector, which would effectively increase the area the hand would have to cover in order to restrict the light falling on the LDR.

Having thought of torches and spotlights, I reasoned that I could use MR16-type spotlights, remove the original bulbs, and fit the LDRs inside.  These MR16 (or, with a different fitting, GU10) bulbs can be expensive, but my local Tesco’s was selling a pack of 8 for £1.25, so I bought those, and got to work on them with a hammer.

I’m not saying I did a neat job – and I damaged a few of the 8 in the process! – but I ended up with three reflector housings for my three LDRs.  Knocking off the fittings was easy, but getting the bulb out was not: these things are evidently put together before the glass front is attached, as the bulb is considerably larger than the hole through which the electrical connections pass.  At first I tried knocking the bulb through into the body of the reflector and breaking it up – a procedure not dissimilar from that of the Egyptians, removing internal organs through tiny holes before the process of mummification – but that proved impossible to achieve without breaking the glass front; so in the end I just broke open a hole large enough for the bulb to come out of.

My original intention was to drill holes in the Theremin case large enough to insert the end of the reflectors, and superglue them in place, but in the end the hole would have to have been an inch (25mm) wide, and there wasn’t enough space inside the case to insert something this big.

So instead I mounted the reflectors on the surface.  I built up a sleeve for each one using 25mm inside diameter O-rings.  These were about 3mm deep, so 4 of them superglued one on top of another were enough to support a reflector.  More superglue ensured that the reflectors stayed in position, and that the LDRs, passed through a hole under each reflector,  were in the right place.

This picture of the back of the instrument shows an arrangement I’ve used in quite a few cases where there wasn’t enough room for the battery inside.  Close to the power socket I’ve stuck a square of velcro, and the battery holder sticks to this.

Having a battery stuck to the bottom wasn’t  a problem, as the instrument wouldn’t be resting on it: the  1/4″ Whitworth nut, glued over the hole through which the Beatbox tuning pot was accessed, is the attachment for a mini silver tripod which I managed to get hold of for 99p on eBay.  This would allow the theremin to be raised from the table top and set at the best playing angle.

I think the tripod gives it a futuristic look – or at least what was considered futuristic in about 1940 . . .

I adjusted the original tripod between these last two pictures to allow the feet to spread out a bit wider, as it was a little unstable, especially with the battery velcroed to the outside.  This just involved a little sawing and cutting and it now stands much better without being in danger of toppling over.

Theremin 1

Apart from the Stylophone, another instrument I’ve always been fascinated by is the Theremin, and I’ve always planned to make one.

I know the project I’m about to describe isn’t a proper theremin, but it has an oscillator, and pitch and volume are controlled by hand without touching it – which are amongst the essential features of  a theremin – so it seemed like a good place to start.

The Theremin is an electronic instrument named after the man who invented it in Russia in about 1920, Lev Sergeyevich Termen,  It’s called the Theremin, not the Termen, as Leon Theremin is the name by which he became known when he came to America in the late 20′s – probably a better representation of the family name, which is not Russian in origin, but French.

LeonTheremin, c.1924, public domain, from Wikipedia

Theremin disappeared back to Russia after just a few years, and did not reappear in the West for over 50 years (1989, by which time he was 92 years of age!), but left designs for his instrument which were manufactured under licence by RCA.

As I see it, there are two essential features of the theremin, pertaining to how it is played, and – more technically – how exactly the sounds it makes are produced.

First of all, as mentioned above, it is normally played without touching it: instead, pitch and volume are controlled by moving the hands nearer to or further from antennae – like radio aerials – on the instrument.  This is a pretty unique feature, and came about because Theremin invented it not while trying to make a musical instrument, but in the course of obtaining an audible response to scientific experiments he was conducting at the Physico-Technical Institute in Petrograd (St Petersburg).

The classic theremin features a vertical, radio-like antenna for pitch control (played by the right hand), and a horizontal loop (played by the left hand) to control the volume.

Secondly, the notes produced by the theremin do not come from the output of a single oscillator: instead, it has two oscillators, which run at radio frequencies (RF), and are too high to hear.  However, if there is a difference between the two frequencies, this produces a third tone, which is much lower and which you can hear.  When the player moves nearer to or further from the antenna, this alters the difference between the two high frequencies, and raises or lowers the audible tone.

(Another electronic instrument invented independently at the same time as the theremin, The ondes martenot, also uses the same principle of two high frequency oscillators producing a third, audible tone, but this is essentially a keyboard instrument  – although it also includes a ribbon controller as an alternative to the conventional keys.)

It is typical to hear melodies played on the theremin which feature a great deal of portamento – sliding from one note to the next.  This is almost inevitable, as there is nothing to guide the player to find the correct note, other than their ears.  Skilful performers can avoid doing this all the time, but it would be a terrible waste not to make a feature of it, since the theremin makes it easy.  It is typical, although not a necessity, for melodies to be quite high-pitched, and players will usually employ techniques that produce vibrato.

These typical theremin sounds – often described as ‘ethereal’ or ‘spooky’, and frequently found in horror or science fiction contexts – are a product of the two important design features described above.  Other instruments have been designed which mimic the sound of the theremin (including my recent SoftPot Stylophone), but unless the sounds are produced by the player’s proximity to the instrument, using the body’s natural capacitance to affect the pitch and volume of RF oscillators, it isn’t a proper theremin.

The Electro-Theremin or Tannerin, developed by Paul Tanner and featured on the Beach Boys’ Good Vibrations, was such a good imitation that people used to think it was a real theremin; but it was controlled by a slider.

According to Google, today would have been Robert Moog’s 78th birthday.  As you can see, they’ve illustrated this with a (functional!) version of his famous synthesizer.

Before inventing this, however, young Robert was heavily into theremins, studying the Leon Theremin-designed RCA model and inventing his own – proper – instrument.

It’s not entirely a coincidence that my SoftPot Stylophone – and the earlier Cybersynth – sound a bit like a theremin, but this was the first time I’d constructed an instrument meant to be played without touching it.

In fact, the particular instrument I built is an ‘optical’ theremin, with pitch and volume controlled by two light-dependent resistors, and the basic circuit was so simple, I had to try it:

This circuit came from Graf’s Encycopedia of Electronic Circuits (Vol. 5, I think), but seemed to me to have something of the look of a ‘Lunetta’ device about it. I’ve already digressed into the history of the theremin, so I’ll save discussing Lunettas for another time.  (If you don’t know what a Lunetta is, start here: https://docs.google.com/document/edit?id=1V9qerry_PsXTZqt_UDx7C-wcuMe_6_gyy6M_MyAgQoA&pli=1#heading=h.6a4696420d74 and here: http://electro-music.com/forum/index.php?f=160).

Anyway, I was sure I’d seen the 4049 chip on which the optical theremin is based being used in Lunetta circuits. I had all the parts to hand – including the 4049 which I had recently salvaged from a project board I’d put together so many years ago I’d forgotten what it was originally for; and even the transformer, which I’d recently bought for another project – and it fitted on a 1” square piece of veroboard tucked inside the case of one of the broken Stylophone Beatboxes I had acquired.

It was ultra-simple – and it worked!  However, once I had finished it and played with it for a while, I realised there were some slight problems in being able to play it effectively; and I also began to wonder how I could make it sound more interesting and varied.

I’ll describe my variations on the basic circuit in a follow-up post.  Information on Leon Theremin comes from Wikipedia and Theremin: Ether Music and Espionage by Albert Glinsky (Foreword by Robert Moog).  The Wikipedia article has a number of very useful links to websites on Leon Theremin and his wonderful instrument.

 

Bits & Pieces 4

I wasn’t expecting to add this post just yet, but I had a stroke of luck which has enabled me to complete the scheme for my mono mixing section which I started writing about when I described the Red Dragon the other day.

I bought a job lot of small SoundLab mixers off eBay which were said to be faulty returns.  I thought I might be able to salvage some parts from them, use bits of them in some way, or even repair them – but it turned out that several of them appeared to be in working order.

Two of them were straightforward 4 channel mono mixers – an updated version of the one I had used before, I presume – so these were immediately used for the left and right channel inputs to the mono mixer, as I described in the previous post.  Generally speaking, I wanted to have the lower tones to the left and higher tones to the right, so my ‘double bass’ stylophone was the first thing to be plugged into the left mixer; the treble stylophone and the SoftPot Stylophone in the right.

More interestingly, the two other working units were the G105C version with ‘microphone effects’ – a delay circuit which I guessed was probably based on a PT2399.  I opened up one of the dead ones, and found that this was the case.

The circuitry was very different from the original SoundLab mixer I’d acquired – all surface-mount components; everything, pots and sockets included, firmly fixed to a single circuit board – and I’m not sufficiently skilled or equipped to be able to repair something like that.  Not only was it not functioning, it seemed to short out the power when the on switch was pressed.

I sawed out the part of the circuit with the PT2399 on it, which didn’t short the power when used by itself, but didn’t do anything to the input sound either.  This section is permanently in circuit when the mixer is operating, so maybe that was why the original unit didn’t work.  In any event, I decided to put the broken ones away for another day, and concentrate on the ones that worked.  The case would find a use later on.

First of all an echo unit is a really useful thing to have – and 2 echo units with 4 inputs is a bonus!

My initial arrangement with these is to have the outputs connected to the new Left and Right Mixers.  The left echo unit is used for instrument input and the output is divided: one half of the output going directly to the Left Mixer, the other half going to the right echo unit, and from there to the Right Mixer.  As the delay time and feedback (number or length of repeats) are separately adjustable on the two units, some interesting stereo effects are possible.

Bits & Pieces 3

This Bits & Pieces post covers a few effects modules I’ve recently made.  These are:

1.  Active 3-way tone control – the ‘Tardis’

2.  Active tone control of unknown origin

3.  Active Low Pass Filter

1.  The active 3-way tone control is standard of its type, I imagine.  I don’t know where I found it – years ago I used to scour back numbers of electronics magazines in the local library and copy out interesting circuits.  No doubt it was one of those.  The circuit diagram looks like this:

and the finished article looks like this:

which is why it’s called ‘The Tardis’ – not because it’s a time-manipulation circuit, which would have been cleverer.

2.  The tone control of unknown origin is unlike anything I’ve seen before or since – or, rather, since the heart of it is quite a high-value inductor, it most resembles a variable bandpass filter – a wah circuit – but is evidently not intended to be swept up and down like a wah wah pedal.

Another of my finds in a very old electronics magazine, it was originally called a ‘Passive Tone Control’, but the reduction in the volume of the input signal was so drastic that I added an amplification stage before it to boost the level to something like the original, and it became an ‘Active Tone Control’.

Moving the single control from one extreme to the other varies the tone considerably, and it’s very useful with sounds rich in harmonics, like the various Stylophones in my collection.

This was another project after the Touch-Radio which I housed in one of the transparent jewellery cases I had recently acquired.

3. I’d heard nothing but praise for Ray Wilson’s simple 741-based low-pass filter – and indeed the whole ‘Wacky Electronic Noise-maker Thingy’ which it forms part of – so I decided to make one and try it out.  In fact, I made two, and I’m glad I did, because they’re great!  One of them went inside an Optical Theremin project, which I’m in the middle of, and which I’ll be describing as soon as I’m finished; the second one went into another jewellery box project.

I hope I’ve interpreted correctly what it says on the Music From Outer Space website, where it comes from, and it’s OK to reproduce the circuit diagram here:

You can read about Your First Wacky Electronic Noise-maker Thingy here: http://musicfromouterspace.com/ - just look for links to ‘WSG’ and you’ll find it. In fact, I just looked at it again and discovered that the circuit there is a slightly more advanced version of the one I built, incorporating fine adjustment of the filter cut-off frequency and a resonance control: looks like I’ll have to go back and make some modifications! . . . Later on I may have to build the whole thing . . .

Note in the diagram above the correct way to wire the cut-off frequency potentiometer.  I used a logarithmic pot, because that’s what I happened to have, which exaggerated the effect of my error the first time I put it together of wiring the pot the wrong way round – no effect throughout most of the travel, then a huge effect in the last quarter-turn: wire it the right way round and you get the full effect through the whole travel of the pot.  Adding a 100k pot, wired the same way round, in series with the 1M pot, at the end marked ’1′ – which is what the slightly more advanced version includes – would help to make more precise adjustment of the tone.

I should add that the whole Music From Outer Space site is an absolute mine of information and worth reading in its entirety: you can learn about synth modules, study circuit diagrams/schematics and buy circuit boards and so forth associated with the projects described.

Once I get round to doing the modifications, I’ll add a comment or edit the post and show a picture of the finished article.

Bits & Pieces 2

This Bits and Pieces post is about mixers.  There is nothing inherently new or exciting in my system, which isn’t complete yet, but it’s building up to something more interesting in the latter stages.

The part I’ve been working on is the section for mono instruments, which works like this:

First of all I started with a small 4-channel mono in-mono out Soundlab Micromixer for £6 or £7 on eBay.

Fortunately, this came with a circuit diagram, so it was easy to add 4 more identical input channels.  These are housed in the ‘Red Dragon’, a Stylophone case from which the innards had been removed (for use, I think, in The Gemini, which is two Stylophone circuits in one body).

The Red Dragon feeds the Micromixer with 9v power as well as the 4 extra input channels (the ones with red caps).  But I like working in stereo, so the 4 extra inputs are switchable from mono to stereo: the stereo side of the switch sends the input via a passive mixer (a 10k resistor on each channel) into the input of a pseudo-stereo circuit, and from there to a stereo output socket.

I’ve lost the circuit diagram and explanation of the pseudo-stereo circuit, but it was published in an electronics magazine in the 1980′s, and I bought and made up a kit version from them.  It may even have been the work of the amazingly prolific RA Penfold.  At the time I used it to listen to mono cassette tapes on my Walkman, and it improved them no end.  An empty cassette box was just big enough for the circuit board, headphone socket and PP3 battery; it was still in this box when I recently found it, and needed only a replacement 741 op-amp, which had evidently been scavenged at some point in the past.

I don’t remember precisely how it works, but it seems to be some sort of frequency-dependent phase-shifter, whereby some frequencies are sent to the left ear, some to the right, spreading a single mono signal throughout the stereo field: perfect for sounds with a rich harmonic content – like the Stylophone, for example.  (Mono instruments The Alien and The Hedgehog are ideal candidates for this treatment).  Which one of the channels is ‘left’ and which is ‘right’ using this system seemed entirely arbitrary to me, so I added a switch to reverse the output channels, according to taste.

In fact, there was room for two more input channel pots on the top of the Stylophone case, but no room for the switches and circuitry beneath, so these two channels (the ones with blue caps) go directly into the passive mixer and pseudo-stereo.

While the stereo signal currently goes directly to a stereo in-stereo out mixer, the mono output goes to a 6-channel mono in-stereo out mixer (a Realistic 32-1210, £10 off eBay) .  This has a balance control on each channel, so the intention is that the section described here will be the centre channel, and there will be further sub-sections for left and right parts of the stereo field.  Later posts will indicate how this works out.

The stereo in-stereo out mixer (£6 off eBay) is a Hama SM502.  Although the inputs of this mixer are marked ‘Microphone’, ‘Magnetic/Ceramic cartridge’, ‘Phono’ and ‘Tape’ (i.e. it’s a mixer intended for a domestic hi-fi!) experiments have shown that they work fine with the signal levels involved here.

Bits & Pieces

I’ve called this post Bits & Pieces because it isn’t about electronic musical instruments, but a few modules I’ve recently made, not all of which are greatly interesting in themselves, but have a use in my set-up.  These are:

1. Extension speaker

2. Headphone Amp

3. Headphone/speaker select switch

These are not highly significant, but I’ve spent time making and using them, so I thought I might as well briefly describe them.

First of all, as you can see, the aesthetic involved is a different one from the projects I’ve described before.  By and large, they’re designed for mono use – although the headphone amp, based on a TDA2822 chip, is for connection to conventional stereo headphones – and they have a deliberately ‘retro’ appearance to emphasise the simplicity of the lo-fi circuitry and sounds they’re used for.

The speaker enclosure – I use the word ‘enclosure’  loosely here as in fact it has no back to it – is something I saw around the house as far back as I can remember: the late 50′s/early 60′s.  I think my Dad made it: I must ask him.  Somehow I seem to have inherited it; and all I’ve done to it is to replace the speaker itself, which had got damaged over the years, with a new one, which is full-range and 8 ohms impedence; and exchange the connectors on the end of the lead with 4mm banana plugs.

The circuits themselves are housed in old tobacco and sweet tins I found in my garage: they came originally from my Grandad’s shed, so are very likely older than the speaker.  (Except possibly the Altoids tin, which strikes me as being somewhat more modern, although I haven’t looked into it).

The headphone amp I made some years ago, from a circuit diagram I now appear to have lost.  The headphone/speaker switch was also found in my garage – possibly a car-boot acquisition: designed for stereo headphones, but used in this set-up only for mono signals, divided and fed to left and right.

The main use of the extension speaker is to get a better sound from instruments with no line out.  To date I have two of these: the Cracklephone and the Touch-Radio.  Both of these have 4mm banana sockets on them, and the speaker leads terminate in banana plugs, so can be connected directly into these instruments.

To avoid antagonising my neighbours too much, especially late at night, I have a pair of banana leads to connect the instruments to the headphone/speaker switch, via the sockets in the Altoids tin, which allows the headphones to be used in place of the speakers.

I didn’t manage to show this in the photo, but the speaker leads from the instrument or amp are connected to the banana sockets on the left of the Altoids tin, the headphone/speaker switch connects via the small stereo socket (in) and large mono socket (out) on the front, and the speaker connects to the banana sockets on the right.

The older Stylophones in my collection would benefit from the addition of speaker sockets: as referred to elsewhere in the blog, most models seem to have additional components in the line-out circuit (filtering out higher frequencies), which gives the line-out sound a different character compared to the tone from the internal speaker.

Much has been written on the Cracklebox, and how it is against the principle of the original Cracklebox to add a line-out.  As I see it, it isn’t a violation of principle to use an external speaker in place of the one built in to the instrument itself: a wider range of volume and tone is available this way.  And that’s what these Bits & Pieces are about, I suppose: creating sounds in a live, old-fashioned, organic sort of way, in contrast to the modern, synthetic, digital way.

The Touch-Radio

The Touch-Radio was, design-wise, by far my easiest project to date.  This was for the simple reason that it’s essentially the circuit board out of an old transistor radio, more or less unaltered!

I had had the radio for about 40 years: about 20 years ago, I took it out of its case – which has subsequently disappeared – and rewired the tuning and volume controls, evidently intending to do something with it.

I forget now whether I ever did – probably not – but I found it again recently, just as I was finishing the Cracklephone, and thinking about touch-controlled sound-makers; so I decided to connect a battery clip and speaker and see if it made a noise.

It did!  And I soon discovered that by touching certain parts of the exposed circuit board interesting sounds could be coaxed out of it – often not entirely unlike the Cracklephone, but with an element of speech incorporated.  Touching the aerial did frequently amplify the received radio signal, but it was rare for speech to become readily intelligible.

So I decided to leave it at that! – apart from putting the speaker, volume control and power in a box, to keep it neat.  A PP3 battery would just about fit inside, but it also has a socket for  external power.

I’d recently obtained some small plastic jewellery boxes, which looked good for small projects (some more are described elsewhere in the blog), so I used one of these.  There was also room for two 3.5mm sockets and two 4mm banana sockets, which I added, as I had done for the Cracklephone, to allow a microphone to be attached to the Touch-Radio or the Touch-Radio to be connected to an external loudspeaker.

I’ve always been interested in manipulating speech sounds, and have a number of projects in mind utilising radios in different ways.  I haven’t started working on these yet, but the Touch-Radio is the first in the series.

The Cracklephone

The ‘Cracklephone’, nicknamed ‘The Blue Parrot’, is my second project recreating a classic design.  The first, The Hedgehog, was a version of the famous Atari Punk Console; this one was my take on the ‘Cracklebox’ (or ‘Kraakdoos’ in the original Dutch).

The original Dutch Cracklebox was created by Michel Waisvisz at STEIM (the Studio for Electro-Instrumental Music) in Amsterdam in the 1970′s.  Waisvisz died in 2008, but his description of the Cracklebox can be found here: http://www.crackle.org/CrackleBox.htm.

This is what it looks like:

Photograph by Sascha Pohflepp.

You can buy one like this from STEIM at http://www.steim.org/steim/cracklebox.php.

Waisvisz’s early experiments with electronic sound were of the type now known as ’circuit-bending’, and the Cracklebox was developed as a natural extension of this: STEIM’s philosophy is very much in favour of low-tech electronic music-making and the ‘creative misuse’ of technology.  In particular they emphasise the importance of human touch in musical performance.  Accordingly, the Cracklebox is based on an early op-amp chip numbered 709 (LM709, MC709, uA709 or MC1709CG), provided with 6 pads or touch points which cause it to oscillate in a not entirely predictable way.

The 709, as a matter of fact, was the first widely-used op-amp on a single chip.  It was invented by legendary designer Bob Widlar – an ‘irrational, eccentric, and outspoken personality’, ‘alcoholic loner’ and ‘celebrated dropout’ according to his Wikipedia entry at http://en.wikipedia.org/wiki/Bob_Widlar.  Whether or not STEIM knew of it, I don’t know, but I feel sure they would have approved of the physicality of his practice of ‘widlarising’ – ‘methodically destroying a faulty component or a flawed prototype with a sledgehammer’ . . .

Be that as it may, the 709, as a very early design in the field, required more external circuitry for ‘frequency compensation’ than later and more familiar op-amps like the ubiquitous 741, so lends itself to greater possibilities of interference by touch.  As people are different, so the Cracklebox sounds different when played by different people – the player and the electronics combine to make a unique instrument between them.  (Indeed, it is possible for two or more people to play the Cracklebox at once, by touching separate pads, or each other.  There are videos on YouTube demonstrating this).

I had been using the computer a lot in recent projects, but the low-tech approach is another strand I’ve been following.  Fortunately, circuit diagrams and advice on the Cracklebox were available at this website: http://www.eam.se/kraakdoos, and there was much discussion of it on the electro-music forum, for example: http://electro-music.com/forum/viewtopic.php?t=11052.

In some places I read that the 709 could be difficult to get hold of, but I had no trouble in getting them from one of my regular sources, Cricklewood Electronics, at a perfectly reasonable cost.  I have also read that the NTE909 works as well, but have not had cause to check this out.

The circuit I used looked like this:

The reason why there are 13 touch points, rather than 6, is to do with the case I built it in.  I mentioned in an earlier post that I had acquired a number of broken Stylophone Beatboxes.  I had used one for the ‘Big Boy’ Stylophone mod, and had been looking for a project in which I could use another.  As the Beatbox has a large and attractive circular ‘keyboard’, divided into sections, I thought this would be ideal for a series of touch pads, as used in the Cracklebox.

The Beatbox keyboard – or as it is now, ‘playing surface’ – has 13  segments, hence the duplication and addition of extra touch points.  The original 6 are marked  *  on my circuit diagram.

As many as possible of the Beatbox’s original switches were retained – mostly with different purposes, of course – and the volume control, in particular, proved useful to keep, as it could be manipulated with the right index finger while playing.  The odd arrangement in the middle of the circuit diagram is designed to make use of this – the first variable resistor sets an average, maximum or minimum volume, and is not much used when playing.

Other additions to the basic circuit are:

- voltage starve.  I added a switch to this arrangement, the idea being that the voltage starve could be applied or not, as required, and there is a choice of direction of turn of the control pot.  After practising with it for a while, I prefer position 3, with voltage starve on, turning clockwise to increase voltage.

- resistor bypass.  There’s only one resistor in the circuit, so I added a 1M potentiometer in series with it, to increase or decrease the resistance between pins 2 and 6.  I know that knob-twiddling isn’t entirely within the philosophy of the original Cracklebox, but I found it a useful addition, affecting the pitch of the sounds produced.

- LDR.  When I had finished, there was an unattractive hole remaining where the Beatbox tuning control used to be.  I decided I needed to fill this in and calculated that an ORP12 LDR was the perfect size to do this.  I put this in series with the 1M resistor, and added a switch so it could be selected in place of the 1M potentiometer.  The effect it has varies considerably according to the ambient light level and the type of sounds being produced: sometimes it acts almost like an on/off switch, allowing for ‘gating’ effects.

The  op-amp section and the transistor section were built on two very small scraps of veroboard to make sure they could be fitted inside the case – there was very little room above the large keyboard PCB.

There is an LED shown in some versions of the Cracklebox circuit diagram.  I intended to incorporate this as shown, but I wired it as an on/off indicator at some point when I needed to know whether power was getting to some parts of the circuit and in the end I left it that way.

Here’s what it looked like when I finished:

As soon I started to use it, however, I realised straight away that the best way to play it was to turn it upside-down, with the keyboard and speaker facing away from me.  This made it easier to touch the playing surface with my finger tips: seeing where they were wasn’t important, as playing was all done by feel.  This meant the underside of the instrument  – now the upper side – had to be decorated, too.  It now looks like this:

In fact, the Beatbox keyboard turned out to be a very good playing surface, allowing for a certain amount of variation in the strength of touch and the possibility of sliding gradually from one touch point to another.

There is much discussion at the links mentioned above about whether a direct output could – or indeed should – be included, and if so, how this could most effectively be done.  As the principle behind the original Cracklebox was that it should be a ‘stand-alone’ device, I decided to deal with this issue by purchasing – for under £2 – a small goose-neck mic.  This plugs into a 3.5mm socket on the rear of the Cracklephone, and is bent to point at the speaker; adjacent to this is an out socket going to the amp.  These sockets aren’t connected to the rest of the electrics in the case, so this is just a simple way to mic the instrument up, enabling it to be amplified or recorded however or wherever it’s being held or moved.

At the moment, I can only get this to work when plugged into my laptop, not through my general effects and amplification system – but I’m working on it.

I also added two 4mm banana sockets so the instrument could be connected directly to a (better) external speaker.  The external speaker arrangement is described in another post.

The working title for the project was the ‘Cracklephone’, since it’s a combination of the Cracklebox and a Stylophone Beatbox.  I liked the look of the blue parrot stickers, and it sounds very reminiscent of a parrot, so it acquired its nickname – also a reference to Sydney Greenstreet’s bar in Casablanca.

Sound files to follow

How I started

I’m writing this Blog to document some work I’ve been doing in the field of electronic music-making.

I wasn’t an expert in any of these things before I started – and I’m probably not an expert in any of them now, but I’ve learned a lot as I’ve gone on, and I hope if I can pass it on it’ll be a source of interest and in some small way an inspiration to others who are getting involved in this field

When I began thinking about this project I decided to do it in the following way:

a).  To avoid working with computers (until the very end).

I’d used computers extensively in my music before, from Logic for straightforward composed pieces to a variety of other programs for electronic composition or sound treatment.  I expected to return to using the computer in the end, but with the benefit – hopefully – of new knowledge and new sound devices.

b).  To incorporate where relevant some projects I’d started, and mostly not finished, many years ago.

I’d made some guitar effects with a degree of success that could be described as ‘mixed’ – some of them I use to this day, which work very well and can’t or don’t need to be replaced by anything new; some are still around, not quite working the way they were intended to; some never worked at all!

So I decided not to go back to guitar effects, but to concentrate on sound producing devices.

c).  To explore certain specific ‘movements’ in electronic sound-producing, such as ‘circuit bending’ and ‘Lunetta’ devices, and construct some of the ‘classic’ designs along the way.

d).  To explore alternative methods of music input – isomorphic keyboards, game controllers, and other home made devices.

One of the intentions behind this was to create music in more of an informal and  ‘live’ way than I had done using the computer; another was to explore the variety of music- and noise-producing devices now available – usually cheaply in sales, second-hand shops and on eBay.

I also wanted to pursue my obsession with the Stylophone, an early electronic synthesiser of the late 60’s and early 70’s, but recently reintroduced.

I’ve divided the different parts of the project into the following categories:

1.  Modification

In this first phase I would take existing devices and add new features, or expand existing ones.

My principle in doing this was understanding the circuits (to a certain degree) and making appropriate changes to produce specific effects.

2.  Construction

Phase 2 was to build a number of sound-producing devices from scratch, using circuit diagrams and descriptions from books and magazines (I had a number of these collected over the years, and hand-drawn circuits copied from publications in libraries) and from the internet.

Again, a certain amount of understanding of the principles of the circuits would be necessary.

3.  Circuit Bending

In this phase the idea was to take existing electronic instruments – children’s toys mostly – and make them produce sounds they were never intended to produce, mostly without worrying too much about the circuits that produced these sounds and how they were working, which I felt was more within the spirit of the enterprise.

4.  Freeform designs

The intention then was to extend the knowledge gained in previous phases to create new designs, partly modified, partly constructed, incorporating past ideas I had had, but never put into practice and new ideas discovered through experimentation.

5.  Software/MIDI

This phase was to be mainly computer-based, involving programming, which I had not done before.

As it turned out, I was overtaken by events, and parallel with the Modification and Construction, have got involved in some slightly different areas.  However, I’ll write about each of my projects in order, and put them in the appropriate category.