29
Dec
11

The Alien – my first modification project

My first Modification project involved a Stylophone – the 2007 re-issue – which I modified as shown below:

1.  Power on/off.  This is the original power switch, unchanged.

2.  Drone switch.  The original vibrato switch with different wiring connected to it.  This switch causes the Stylophone to sound without using the stylus – useful in conjunction with some of the other modifications for which you need free hands.

For anyone interested in the details, I didn’t manage to document the whole procedure, but I’ve got a couple of pictures of the inside.  This one shows the end of the main circuit board and the small board for the power on/off and vibrato switches.

The original wires to the vibrato switch were disconnected, but not the other wire to the small circuit board, which goes to the Power switch.  As it’s a three-way cable, it might be easier to disconnect all of them, bend the two vibrato wires out of the way, and then reconnect the other one.

The pole of this switch (the middle of the three tracks) was attached to the highest note on the keyboard.  Each note has a small round spot where a wire can be connected, and you can see the spot for this note nearby on the keyboard circuit board.  The ‘on’ end of this switch is attached to the point where the stylus wire is connected to the third circuit board inside.

(In the picture, where it says ‘connect the end one to the end of the stylus wire’, it means the end track on the circuit board, not the end of the wire itself, which is going to be used for something else later.  Note that both these switches are SPDT, but used as SPST, with one end not connected).

3.  Tone.  This is the original 3-way tone switch, unchanged.  It’s a double-pole switch, with only one side used, so there ought to be plenty of scope for adding functionality to it.  I tried adding momentary switches linking the three wires that go back to the circuit board, for brief tone bursts, but in the end didn’t leave them in as it was hard to find one that worked in each of the three tone settings.  Adding potentiometers didn’t seem to have any effect.

4.  Feedback loop.  This switch and potentiometer are wired to two places in the output circuit of the Stylophone.

The switch turns Feedback on, producing a continuous high-pitched sound, adjustable by means of a 220k Log potentiometer.  When using the stylus with this circuit on, very interesting tones are produced as the feedback tone modulates the note played with the stylus.  In Drone mode, a ‘double’ tone is produced, very rich in harmonics.

Once the feedback wires are attached to the circuit, even with the switch off, a hint of the high-pitch breaks through to the output, and there’s a hint of the modulation when notes are played with the stylus.  Apart from this one effect, ‘The Alien’, as it is known, can be used with all the switches off as a normal Stylophone, with variable rather than fixed vibrato.  Feedback is such an effective tonal modification, though, I didn’t want to leave it out.

5.  Wide-range pitch control.  This is a 2.2M Log potentiometer which allows the pitch to be changed from a very high note, to a very low note – so low, that it hardly seems a pitch at all, almost a beat.  Can be useful!

6.  Pitch Effects on/off.  This switches the Stylophone’s pitch control out of the circuit as well as switching on the modified pitch effects.

7.  Wide-range pitch control on/off switch.

These 3 controls were the most difficult to arrange, especially as I wanted the Stylophone’s original pitch control to be used as normal when it wasn’t switched out of the circuit by 6.  This meant breaking the original connections to the pitch potientiometer and putting in some new ones.

The other difficulty was that the Stylophone doesn’t mind going right down to a very low pitch, but doesn’t like going up too high.  If you try to make it go too high, it will cease sounding and you can only get it to work again by switching off and on, or in some cases switching off, removing the batteries, putting the batteries back in and switching on again.  This is a common phenomenon in circuit bending, but I didn’t install a battery cut-out switch, as is often done – there’s no need for this to happen, even with all the modifications working, so it could be designed out.

Accordingly, the wide-range pitch control doesn’t go all way from + v to 0v, but is connected to +v by a variable resistor, enabling you to set the highest note it will be able to produce and stop it from going silent.

This diagram shows how the rest of the connections to the switches are made and shows three preset variable potentiometers which are used.

Note that I found it easier to connect the 3 presets to the TOP side of the circuit board, rather than the side in the picture, with the components on it.  The Stylophone’s pitch control does face this way, and it’s easy to find space on the tops of the two legs to solder the potentiometers.  You just have to make sure they’re out of the way when you put the back of the Stylophone on again.

Make sure when turning the circuit board over that you identify the correct two legs.

To adjust them, start by setting them to mid-position.  Switch on the part of the circuit connected to each one – e.g. the wide-range pitch control – turn it up to maximum pitch and adjust the preset upwards to the point just before it goes silent.  There’s a small area just before this where the tone starts to degrade, and you could turn the preset down a little so this is never reached in normal use.

The original pitch control is somewhere in mid-position in normal use, but don’t forget this may be working in some settings, and may have to be turned up when adjusting the presets.

Once this has been done once, it won’t need doing again.

9.  LDR (Light-dependent resistor, photoresistor or photocell) and LDR on/off switch.  The LDR is a NORPS-12, which has wide resistance range.  The less light that falls on it, the lower the pitch.  It depends very much on the ambient light how close you need to put your hand to it to achieve useful effects, but in many circumstances I’ve found very close – even to the point of touching it.  This is not a bad thing, as you don’t have to stand away from it to stop it working, and it almost resembles a touch switch in this way.

A handy accessory to have is a small torch, with which you can raise the ambient light level and increase the pitch by shining it on the LDR.  I have an LED-based cycle light – 99p from a supplier in Hong Kong – which is very bright, and also has a number of flashing modes, which produce LFO-type effects.

8.  Variable vibrato.  Connect a 1M Log potentiometer between the two wires you disconnected from the power/vibrato board. This gives a transition between full vibrato and no vibrato at all.  Only two of the connections on the potentiometer are used, and you might want to experiment with which of the end ones you use as the degree of control is different, and I can’t remember which way round I put them.

The Stylophone’s volume control (next to the LDR switch on the right hand side, not pictured) was left in place, and still functions as before.  It has no effect, however, when Feedback is on.  You must do as we did with the original Stylophone, which had no volume control, and put your hand over the speaker!  And watch out when using earphones!

General construction notes

1.  The first thing is that the top and bottom halves of these reissue Stylophones don’t come apart easily, like the old ones did.

The old ones were powered by a 9v battery which was on the inside, so you had to take them apart easily to replace the battery.  The reissue ones take 3 AA batteries in a battery compartment which is accessed from the outside with a cross-point screwdriver, so the top and bottom are superglued together.

The 4 main points where they’re glued are near the corners on the long sides, and there is no alternative but to insert a knife or screwdriver in the gap and prise it open.

2.  The black blob hides the main processor that does all the sound generation.  It seems a little sensitive, so avoid soldering near it for all but the briefest time, and don’t solder with batteries in.  I managed to ruin a couple, almost certainly by doing one of these two things.  In particular, be careful when connecting the drone switch to the keyboard circuit board.

3.  I also painted the base black and superglued a metal alien face to the front.  Neither of these things has in any way improved the sound, except insofar as the effect it has on the mind of the player.

The alien face, by the way, actually comes from Roswell, New Mexico in the USA, site of the original UFO flap in 1947.  How much more authentic can you get!

Acknowledgements

Some useful pointers came from a well illustrated article by TraceKaiser on the www.stylophonica.com forum; and from circuit-bender Freeform Delusion, www.facebook.com/pages/freeform-delusion/144587583120.

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andymurkin

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