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Optical Theremin

R

rr5025

Nov 12, 2008
848
8
#1
Forgive me if this has been posted before, I did a search and didn't seem to turn up anything.

I want to add one of these guys into my first bass (this guy is pretty much going to be just a mess around one). And had a few questions.

I should start off by saying I do know a decent bit about electronics, I took a few classes in high school and enjoyed it. Unfortunately that was a few years ago so I'm a tad rusty and could use a refresher or two.

The line out on this guy would go to the jack correct? How would that be hooked up? Also I was toying with the idea of adding a pot for volume, where would that go in?

I know there's a stomp box out there like this but I wanted to throw my own together and just have something to make a few crazy noises. If anyone has done this before I'd love to hear a few tips.

Plans are here

Cheers!
 
#4
I own a theremin and love playing with it, but I've got no idea what an optical theremin would look like or how it would even work - let alone how you would incorporate it into your bass.

Sorry that I can't be of more help in that department.


As far as adding a volume knob, that can simply be done with a (probably 500k) pot right before the output. Set it up like a normal volume pot with - | + | ground.
 
#5
FunkMetalBass said:
I own a theremin and love playing with it, but I've got no idea what an optical theremin would look like or how it would even work - let alone how you would incorporate it into your bass.

Sorry that I can't be of more help in that department.


As far as adding a volume knob, that can simply be done with a (probably 500k) pot right before the output. Set it up like a normal volume pot with - | + | ground.
Click to expand...

Thanks I'll have to toy around with this when I get a chance to snag the parts. I guess I'll have to be a trailblazer and post my work :ninja:
 
#6
Ok another question, well two. Both are relatively simple.

First what part would connect to the ground. I don't see a ground symbol on the schematic anywhere.

Second what would I add to make it take a 9v battery? I know I need a voltage divider but just don't know where to put it.

Cheers
 
#7
rr5025 said:
The line out on this guy would go to the jack correct? How would that be hooked up? Also I was toying with the idea of adding a pot for volume, where would that go in?

Plans are here

Cheers!
Click to expand...

Yes, this could work in a bass. If you use the circuit board you could mount it in the cavity. Use the bass's 9v battery for supply (instead of the 6 v. listed) if it's an active bass. I'd take the two photodiodes (the two of them make ONE light detector) and mount them somewhere on the bass where they can see light (on the upper horn?) and you can easily reach them to block the light with your hand to modulate the tone. I'd put a switch on the power as well as a volume control.

Adding a volume control might be tricky. The volume control goes on the output. Connect the outside pot terminals to Output and ground and then the slider (center terminal) will go to the bass output jack. But here's the problem. When you turn down the theremin it will short out the bass output! Thus you'll need a resistor to properly mix in the two signals. I'd try a volume pot of maybe 100k to 250k and a series resistor between the center lug (slider) and the hot on the bass jack of maybe 200k to start. You may have to experiment with values depending on how loud/soft the various signals come out.

Good Luck.

PS. Yes, I do own a theremin that I built from a kit. Too cool for words! Mine is a "real" one rather than "optical".
 
#8
rr5025 said:
Ok another question, well two. Both are relatively simple.

First what part would connect to the ground. I don't see a ground symbol on the schematic anywhere.

Second what would I add to make it take a 9v battery? I know I need a voltage divider but just don't know where to put it.

Cheers
Click to expand...

Ground is the lower terminal on the "output". The one that goes to the "-" side of the battery. That goes to body of output jack and shielding. Note that in a bass you'd connect the "-" side of the 9 volt battery not to ground but to the "ring" terminal of the bass jack. (requires a 3-terminal stereo jack) By doing that, it acts as a switch so that when you pull out your guitar cord it disconnects the battery. Most active basses work this way.

I don't think anything is needed to run this on 9 volts. Especially an Alkaline "9 volt" battery which are slightly lower voltage than standard batteries. I looked up the rating of the 555 IC and it easily runs on 9 volts. The only question would be the voltage rating of the phototransistors. If they die then just replace them with the suggested cadmium sulfide bathroom light cell. I don't think you need a voltage divider.
 
#9
I was thinking about doing the same thing today. I have a passive Stingray copy that has a lot of space on the metal control plate. My thought was to add a separate output jack for a separate FX loop and amp, an on/off toggle and a volume pot. I hope you're posting pics and sound clips when you're done!
 

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