Pitch Bender

Cynosure

What do you use for bender the pitch on your DIY synths? The local electronics shop said they didn't have anything that would work.

I was thinking about maybe trying to get an EQ pot to use. They have a notch in the middle so I know when it's back in the center.

I tested it out, and a 1K pot is way too much resistance. I need something with very little resistance. Or I might be able to use another pot that controls how much the bender effects the current.

Is there a better options that has linear resistance across the entire range, but somehow returns to center easily?

XCenter · Joined: Oct 01, 2005 Posts: 113 Location: Germany

What about Doepfer?

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http://www.doepfer.de/zubeh_d.htm#Modulationsr%C3%A4der

Cynosure · Posted: Sun Jan 23, 2011 11:20 am Post subject:

That would be ideal, but I'm looking for an inexpensive option. I'll check the local synth shop this week and see if they have any of those kicking around for a decent price.

richardc64

Cynosure · Posted: Sun Jan 23, 2011 5:05 pm Post subject:

I am working on a top octave synth that uses 2 sets of 2 40106's to create the top octave, which is then divided by a bunch of 4040's.

I tested a 1K pot on the power supply going to the 40106's. Adjusting it changes the speed that the capacitors on the oscillators charge up, which changes the frequency of the oscillation. But the 1K pot varied it too much.

Dan Lavin · Posted: Tue Jan 25, 2011 8:28 am Post subject:

Just to clarify, are you using the 1K pot as a voltage divider? In other words is one end hooked to +V and one end to Gnd with the wiper hooked to the voltage supply of the 40106's?

If that's the case, you could add another resistor between the bottom (where ground is currently connected) and run the other side of the resistor to ground. This would limit the voltage swing to the 40106.

Cynosure · Posted: Wed Jan 26, 2011 8:15 am Post subject:

Thanks Dan. That's what I was thinking of doing, but use a variable resistor so I can control how much the first one changes the pitch. That way I could bend the pitch a few semitones or an entire octave.

But what I need is a pot that I can return to the center so I know when the oscillator is back to the note that I have it tuned to produce. I checked 2 music stores, an electronics shop and a surplus shop that has a lot of electronics. None of them have anything I can use. I might have to order something on the net, which usually means I have to pay shipping and brokerage and it ends up costing a lot more than it's worth (unless I can find someplace in Canada that has it).

Inventor · Posted: Wed Jan 26, 2011 8:19 am Post subject:

Dan Lavin · Posted: Wed Jan 26, 2011 9:17 am Post subject:

You could use this mini-joystick from Spark Fun. It's pretty cheap and you could maybe use the other axis for control modulation?

Put in in series with a regular adjustable pot to set the range of the pitch bend.

http://www.sparkfun.com/products/9032

inlifeindeath · Joined: Apr 02, 2010 Posts: 316 Location: Albuquerque, NM

thats what i was going to suggest Smile

you could also salvage an old video game remote. The thumbsticks are identical to that part.

Cynosure · Posted: Thu Jan 27, 2011 7:24 pm Post subject:

That's perfect! I picked up a used controller today and tested it out. It actually has too little resistance, but maybe another resister inline will help - or I can try swapping the trimpot in the joystick with one of a higher value.

Thanks!

fonik · Posted: Fri Jan 28, 2011 4:43 am Post subject:

or try to find a defective MIDI controller keyboard. i buddy gave me one for free and i salvaged the pitchwheels and the fatar diode matrix keyboard from it...

richardc64 · Posted: Fri Jan 28, 2011 5:52 am Post subject:

I extracted the circuit below from something that starved a 40106 and a quad XOR, so it should work with 2x 40106. The transistor can be any g.p. NPN. You'll have to tailor the resistors to the pot you want to use.

But there may still be a problem: getting all 12 oscillators to change by the correct amount to maintain that 12th root of 2 per semitone relationship. That's why this http://electro-music.com/forum/topic-45583.html is a much better idea. Yeah, it's 10 more ICs than two 40106s, but you wouldn't have to mess around with different R and C values and only one oscillator has to be varied for Range and Pitch Bend.

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Cynosure · Posted: Fri Jan 28, 2011 6:14 am Post subject:

Thanks Richard. I saw that thread for the other top octave synth, but I had difficulty dividing the notes. I don't really understand how it works and when I tried to replicate the schematic I didn't get the same result. I don't know how the 4040 is able to divide by semitones. Maybe I'll try replicating it again to see if I can get it to work for me.