Transistor Organ


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This simple circuit can provide hours of enjoyment as you learn tunes, play duets or just make some really weird sounds by pushing all the buttons at once. You have probably seen this ciruit before, it is fairly common. I have seen it in several books. The best thing about the circuit is that you can tune each individual note, or go to a whole new octive by changing one capacitor (C1). Because of this, it is possible to from an entire Transistor Organ ensemble. Why you would want to do this is anyone's guess...

Schematic

This is the schematic of the Transistor Organ

Parts

Part
Total Qty.
Description
Substitutions
R1-R88250K Trim Or Regular Pot
R9, R122100 Ohm 1/4 W Resistor
R10110K 1/4 W Resistor
R111220 Ohm 1/4 W Resistor
R1315K Pot
C110.01uF Capacitor
C210.1uF Capacitor
Q112N4891 Unijunction Transistor
Q212N2222 Transistor2N3904
S1-S88SPST Switch
SPKR18 Ohm 2 W Speaker
MISC1Wire, Circuit Board, Knobs For Pots

Notes

  1. You can tune the organ to any instrument by adjusting R1-R8. I used a clarinet to tune mine, but you can of course use any instrument you wish.
  2. The circuit may drain a 9V battery fairly quickly at full volume. You may remove R11 for even more sound.
  3. You can rig up a relay and a foot switch to change C1 (for a different octive) while your playing.

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Comments

dan
Transistor Organ
Monday, May 04, 2009 5:38:12 PM
just finished a school project on this circuit. works great! best regards, dan
anonymous
Transistor Organ
Monday, January 26, 2009 11:53:13 AM
Hello! The 2N4871 is work in this circuit in a place of Q1 ?
Batman
Transistor Organ
Thursday, January 22, 2009 7:45:53 PM
If you're planning to use a 2N2646, make sure you flip the bases (i.e. base 1 should connect to R12/R13 and base 2 should connect to R9) otherwise it won't work.
Brenton
Transistor Organ
Sunday, December 28, 2008 11:47:47 AM
So the octave change is as easy as changing one capacitor right? what should the value be? is there and equation? a power of 10 to the capacitor value? and secondly this organ is monophonic right?
anonymous
Transistor Organ
Monday, November 24, 2008 8:22:17 PM
I used MU-10 Unijunction transistor just to get it to work. But, the volume is kinda low even at gain set at the highest. How can I get higher volume still using 2N2222? I used MU-10 because I couldn't find the one listed above and 2n2646 didn't work either. Thank you.
K
Transistor Organ
Wednesday, November 19, 2008 3:00:28 PM
I couldn't find 2n4891. So, I am planning to use 2n2646. Has anyone tried this?
Michael
Transistor Organ
Friday, October 24, 2008 12:42:02 AM
Hello P. Dont connect the line-input INSTEAD of the speaker! Just short circuit the speaker leads (or even let the speaker in the circuit) and use both sides of R11 to feed into your next stage! Regards Michael
p.
Transistor Organ
Thursday, May 22, 2008 1:00:58 PM
Can anyone give advice on substituting an audio output for the speaker - something I could plug into a mixing board or an amp? I'm starting out with a simpler, 1-tone version of this project. I've got it working fine with the speaker, but when I use the line out instead, I only get sound from a small range in the middle of the potentiometer. If I turn it too far either direction I get a mix of silence and rustling sound (like wind on a mic or a dirty pot). Any assistance would be great. Thanks.
kadry
Transistor Organ
Sunday, March 09, 2008 12:57:16 PM
hi there, i am doing a project on this circuit, and was wondering if you have a booklet or any amount of information on this circuit.for example the way it works and all the specifications and conclusions considering it.i would appreciate it greatly. thankyou
anonymous
Transistor Organ
Wednesday, February 27, 2008 11:53:25 PM
I'm having some difficulty troubleshooting this circuit and I'd appreciate any ideas. I used the NTE6409 alternative and 8 500k pots instead of 250k's. Also I used an audio-taper pot for R13. The rest of the circuit is as described. How sensitive are the pot parameters and the capacitor parameters in getting an audible oscillation? I'm also using #26 wire, which may be on the thin side. Any responses in the comment section would be great!
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