Parabolic Reflector Microphone 2

After creating my first parabolic microphone system (described in this post), I came across a small commercial device which I thought might be worth trying.  It was hard to say if it was really just a toy, but it looked a bit above that, and had some features that made me think it could be of practical use.

This is the box it came in:

and these are the contents of the box.  Clockwise, we see the approximately 20cm parabolic dish, a pair of decent over-ear headphones, the body of the device, and the quite thorough Instruction Manual:

And, when put together, this is what it looks like.  You can see the revolver-style handle; the ‘trigger’ which turns the microphone on; and the two buttons which record and play back the sound picked up by the microphone, which is in the end of the enclosure on the right,  pointing back into the dish.  Along the top is a x8 magnifier, designed, according to the instruction manual, to allow you to see more clearly what is being recorded.  In the base of the handle is a space for a 9v PP3 battery:

It’s not necessary – or, from my point of view, useful – to use the device’s own recording ability, which is only a 12 second burst.  However, you can also see a 3.5mm output socket in the bottom centre of the device.  This can be used with the headphones supplied, to monitor recordings as they’re being made, or to transfer a recording to a computer or external recorder.  More importantly, it can be connected to an external recorder, while the device is activated, allowing recordings of any length to be made.  Monitoring can be done via the external recorder’s system.

I decided to take the device apart and make a few small changes.  There were three reasons for this.  First of all, I wanted to add an option to replace the internal battery with an external socket, as with the other preamps I use while recording; secondly, I wanted to replace the momentary ‘trigger’ switch with a slide switch, which wouldn’t need to be held down all the time I was recording; and thirdly, I needed to replace the knob on the ‘Frequency Controller’ potentiometer – some kind of filter, I presumed, which was designed, according to the instruction manual, to remove unwanted background noises.  This knob was very stiff and well-nigh impossible to turn, not because of the potentiometer itself, but the design of the knob.

So, I decided to open up the device and look inside.  This involved removing half a dozen screws on the opposite side from that pictured above.  The device seemed solidly contructed, and the plastic had a nice feel to it, like a high quality game controller.  This picture shows what was inside.

1 = The small electret microphone element; 2 = the main circuit board with the large record/playback i.c. and the Frequency Controller potentiometer; 3 the switch board with contacts operated by the trigger mechanism; and 4 = the PP3 battery compartment and clip.

The only place which was still firmly connected was the microphone enclosure.  To get the two halves of the body apart I had to saw carefully through the enclosure at the point shown by the arrow.

Fully opened up, this is what the device looked like:

A closer view of the circuit board shows, in the bottom right-hand corner, the two connections, ‘SWITCH’ and ‘GND’ (Ground, or 0v), which I needed to get at.

This view of the other side of the board shows, in the top right-hand corner, where I made connections.  1 = The two switch wires, which went to a new slide switch attached to the upper part of the handle, within easy reach of my thumb; 2 = The ground connection, which went to a new 3.5mm power input socket further up the body of the device, via an LED, which I added to indicate when the device was activated.

In the bottom left-hand corner you can see the ‘Record’ and ‘Play’ buttons, and the LED which indicates when the device is recording to its internal recorder.

I cut the +9v lead from the battery clip to the circuit board and connected both ends to the LED and a new 3.5mm power in socket.  This was a switched type, so that the device would use an internal PP3 battery, unless a plug was inserted in the socket, in which case the internal battery would be disconnected and power would be taken from an external source.  I attached a small square of black velcro to the outside of the device, close to the socket, for this purpose, as I had done on my other recording preamps.

This picture shows the 3 changes I made to the device.  From front to back you can see: the ‘Record’ switch (recording to my external machine, that is, not the device’s internal chip) and indicator LED; the new, easier-to-use Frequency Controller knob; and the 9v external power socket.

As seen in the previous picture, one of my PP3 battery assemblies with integral 3.5mm plug is fixed to the velcro on the side of the device:

These changes should make the device more practical for me to use.  At some time, when circumstances are more favourable, I’ll try it out in the field.

Edit: I recently had a chance to do that, and it turned out well!  The recordings were reasonably noise-free and you hear, as I move through 360 degrees, a certain amount of directionality as the recorded sound changes.

The Binary Winder

I’d been planning a circuit which required a rapid input of binary numbers, ideally from a microprocessor, and it occurred to me that this could be a useful companion to the Bigfoot sequencer or the Chessboard Keyboard  – both methods I was using for sending binary data to keyboards and other devices.

I figured that this could be done manually by using a 16-way hex switch with no end stop – as they are commonly found – and a winding handle as used for re-stringing a guitar.

I bought a couple of these very cheaply on eBay:

and glued the switch inside the body of the string winder – the part which normally fits over the guitar machine head:

This would be the part of the device which did all the work.  Connecting +V to the common pin of the switch would enable it, as it was turned by the handle, to output the 16 binary numbers from 0000 to 1111.

The actual circuit itself was built inside one of the small transparent plastic boxes – described as ‘jewellery cases’ – which I had previously used for small projects such as the Touch-Radio and various effects devices.

In the above pictures the 16-way switch can be seen on the right-hand side, the 5-pin DIN binary output socket at the bottom, and 4 LEDs at the top to indicate the binary number.

The purpose of the 4 DPDT switches in the middle is to change the order of the 4 bits of the binary number.  This was so that winding the handle wouldn’t just produce an output running up and down the scale, but could be changed to give a bit of variety.

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The actual circuitry consisted essentially of passing 9v to the 16-way switch, and the outputs of the 16-way switch to the 4-pin DIN socket via the 4 DPDT switches and a 4050 output buffer.

There was space inside the case for a 9v PP3 battery, so I included a battery clip inside, but also added a 3.5mm socket for external power.

As with many of my devices, I stuck a square of velcro on the back of the box so that a PP3 battery in a holder could be attached.

Space was a little tight inside, but not enough so to cause problems, and after some time the switches were all connected together with the 4050.  I didn’t bother with a circuit board, but just soldered all the connections to the 16-pin i.c. holder which the 4050 was plugged into.

Surprisingly, the case  closed without difficulties, and I was able to test it out with a couple of recent devices with binary inputs, The Telephone and the Carousel Keyboard.

In fact, there is a limit to how quickly these devices can respond to the winder – especially when the pitch is lowered, which seems to slow down the instruments’ responses as well.  However, it was very effective indeed in creating an instant sequence more quickly and accurately than it could be played on a keyboard – especially a keyboard with tiny keys like the Carousel.

The Animal Band & The Telephone – 2

This post actually concerns The Telephone, to which I decided to make a small further adjustment.

After finishing the Animal Band and The Telephone, I realised it would be a bit limiting to leave them playing in only one key, so I went back to The Telephone and searched for the resistor which controlled the pitch of the notes.

Having found it – by means of the tried-and-tested wetted finger method – I removed it from the circuit board and replaced  the connection with a pair of wires.

In the past I had replaced such a resistor with a potentiometer, enabling continuous – and wide-ranging – adjustment of pitch.  In this instance, however, I just wanted to be able to tune The Telephone to other keys, so instead of a potentiometer I added a 12-way rotary switch, the idea being to tune each step precisely to each key.

The Telephone was in the key of B – B being the lowest note it would play.  Rather than make this the lowest key and have all the others higher, I thought it would be better to have B in the middle, with some of the others lower, and some higher.

After some experimentation, I concluded that the difference in resistance between one note and another was just a few k.  I had a number of spare 10k trimmers, so decided that these could be used.

I connected one of these between each of the 12 pins on the switch.  The last one was connected to the circuit board on one side of where the original 100k timing resistor had been; the pole of the switch was connected to the other side, via a 100k trimmer to bring the resistance roughly into line with the original.  In this way, when the switch was at position 1, it would connect through the 100k trimmer and the first of the 10k trimmers; at position 2 the value of the second 10k trimmer would be added; at position 3 the value of the second and the third would be added, and so on to the end.  The way it worked, the more resistance, the lower the pitch.

In the end, I couldn’t reduce the resistance enough to have B right in the middle – the device wouldn’t operate at the highest frequency required for that – so it ended up in 4th position on the switch.  It was quite OK to go down another 8 semitones so that any key could be selected while The Telephone was being operated by the Bigfoot sequencer.

I found a suitable knob to go on the switch, and put The Telephone back together.  Enabling it to be used in any key would make it a much more versatile addition to the collection.

The Black Widow Mk III MIDI

I described first of all the creation of the Black Widow Sample Player and Manipulator, and then some significant improvements in The Black Widow Mark II.

The improvements made in the Black Widow Mk III add to the ease and accuracy of use by adding MIDI control.

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The particular device I had in mind was my trusty Korg Nanokontrol v1, which I use for a number of other applications such as  the FXBOX and the REplay PLAYer .

With 9 sliders, 9 rotary controls and 18 buttons, the Nanokontrol gives access to a large number of parameters. All I had to do was link the CC  numbers output from the Nanokontrol to the inputs of the controls in the Pd (Pure Data) patch for the Black Widow.

In this case I didn’t need to use the Korg Editor application to reassign any of the default CC numbers, I just needed to use the default numbers appropriately in the Pd patch.

For the most part, this just meant creating a duplicate set of controls accepting MIDI input from the Nanokontrol, alongside the controls accepting ‘hid’ (Human Interface Device) input from the Black Widow throttle/joystick.  These are typical examples:

In the same way as the ‘hid’ inputs, all 4 samples can be operated by the same button, slider or rotary control; exactly which sample is to be affected is chosen beforehand.  Due to the complexity of the selection page relating to the ‘hid’ controls, the MIDI controls have been placed separately, but the typical output – e.g. [s filter1], [s filter2] etc. are identical to the outputs of the ‘hid’ controls elsewhere.

The main page of the Black Widow Pd patch has been changed to reflect the new additions:

At the same time, there have been a few other updates, including provision for the file names to be displayed on the Sample Monitor screen and improvements to the Track Active and Reverb/Echo on/off indicators:

These various updates have taken the current version number to 37.  This or a later version of the patch can be found here.  [Click ‘Save Link As’].

Alternative Keyboards 5 – postscript

[Note: this post was originally a comment I appended to the post ‘Alternative Keyboards 4‘, which was about my double QWERTY keyboard instrument.  In that place it was hard to find, and the illustrations disappeared when I changed my website, so I’m trashing the comment and transferring the text and images here].

In order to play the ‘blue’ keyboard (the left-hand one) properly, the Shift key needs to be pressed down so that it outputs different ASCII codes to the ‘red’ (right-hand) keyboard. Using ‘Caps Lock’ doesn’t work, as this only affects the letter keys, not the numbers or other characters.

It would be awkward to have to press the Shift key at the same time as pressing a note key every time, so this keyboard needed something to keep the Shift key pressed while playing. I didn’t want to do anything permanent to the keyboard, like gluing the key down, so I looked for a suitable clip, which could be slid on and off when needed.

There are two types of clips that do this job: a drawing board clip, used by artists and architects; and a table cloth clip, as used in the home. They all look something like this:

For a drawing board or table, the flat side would be on top and the bent side, which acts a spring, putting pressure on the end and holding it tight, would be out of the way underneath. For my application, I needed to use it the opposite way round, with the flat side underneath, so the keyboard could still stand on the desktop in the usual way.

I liked the look of the drawing board clip best, but in the end I found some table cloth clips in the sale in a local home shop, and bough those. They looked like this:

Because i thought they stuck up rather high and might interfere with playing, I experimented with bending them into flatter shapes. This is the one I currently use:

In this way, the ‘blue’ keyboard outputs different ASCII numbers from the ‘red’ keyboard, and can be interpreted separately by the program Pure Data which I use with the ‘double-keyboard’ arrangement.

Guitar FXBOX – Part 3, developments

After finishing the FXBOX foot controller, I started to use the FXBOX and soon decided on a few changes to the software.  There are now 3 areas in which there are differences from the original description of the software in Part 1 of this series of articles.

1  I had been using external pedals to add and change pitches, so I decided not to implement the ‘Pitch’ function.  I’ve left a reference to it on the main FXBOX screen, as it’s still for the time being referred to on the foot controller – and I may decide to bring it back in future.

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2  The next change can be seen in the bottom right-hand corner of the main screen.  In order to enhance the shimmering effect of the spectral delay and the freeze I added a simple looper.  This would enable the delay and freeze effects to be repeated continuously, providing a background for melody or other sounds.

I added a half-speed and double-speed playback facility, to allow for some variation in the sound produced.  The double-speed is particularly effective for higher-pitched ‘tinkling’ sounds.

Section 11 of the foot controller, which wasn’t being effectively used, was altered to allow for hands-off control of the various loop functions.

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3  I added MIDI control for changing the variable parameters – volume, mix, chorus rate, depth, and so on.

I have a set of the original Korg ‘Nano’ controllers, NanoKeys, NanoPad and NanoKontrol, so I used the NanoKontrol for this application.  (This is a great device – very useful and usually quite cheap on eBay.  Versions 1 and 2 seem quite different in various respects, but I don’t think it would matter which you used for this application.  Version 2 doesn’t have the ‘scenes’ concept, but something else instead, I believe).

First of all I used Pure Data’s [ctlin] object to separate the incoming MIDI Channel, Continuous Control (CC) Number and Value information:

then sent that information to control the values which would normally be set when the program opened, and altered by hand on the main screen –  a fiddly operation, on  top of having to stop playing in order to do it.

Here are a couple of examples of how it was done.  The calculations after the receipt of ‘midivalue’ are to translate the MIDI scale of 0-127 to the scale of the parameter being changed, which might be 0-1, 1-100, 1-128  or anything else.  The [loadbang] instruction ensures that, in this case, envelope sensitivity is only affected when CC Number 14 is received, and envelope attack is only affected when CC Number 15 is received.

As well as the CC Numbers having to be carefully specified, it was also important to ensure that the FXBOX responded only to messages on its own MIDI channel.  I used Scene 1 on the NanoKontrol; I can’t remember if MIDI Channel 11 was the default, or if I changed it to that using the Korg Editor:

In any event, it was set to Channel 11, and I amended the Setup screen so that the MIDI Channel received by the FXBOX could be changed:

The revised files required to operate the FXBOX (the foot controller and MIDI control are entirely optional) are here:

http://www.andymurkin.net/Electronica/FXBOX/abswitch~.pd

http://www.andymurkin.net/Electronica/FXBOX/crossfader~.pd

http://www.andymurkin.net/Electronica/FXBOX/expression.pd

http://www.andymurkin.net/Electronica/FXBOX/FXBOX22.pd

http://www.andymurkin.net/Electronica/FXBOX/Guitar_specdelay~.pd

http://www.andymurkin.net/Electronica/FXBOX/LoopGenerator.pd

http://www.andymurkin.net/Electronica/FXBOX/midiin.pd

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This edited improvisation gives an idea of the sounds the FXBOX makes:

2014

Sorry if you’ve been following the blog and have noticed there have been hardly any posts this year.  I’ve been ill – almost fatally – but have recovered and should be writing again in the new year!