theremin sounds like a cello

Posted: 3/18/2012 3:56:49 AM
invisiblejelly

Joined: 3/18/2012

Hi all I recently bought an etherwave standard and tried to get a cello like tone out of it but couldn't get it going all through the octaves.So I took out one of those small capacitors coming from the two main oscillators and put in a bunch of diodes and kept putting them in till I got what I thought was a nice cello like sound that went all the way up the octaves (about 4 and 1/2 octaves which is what I like to play with).

http://soundcloud.com/invisiblejelly/theremin-test-7-cello-like

the above is a recording of what it sounds like which was recorded only from a small mike on my computer.

Posted: 3/18/2012 5:40:48 AM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

Nice hack!  I think it sounds great.  Would you mind posting a picture of the board with your diodes in place?

Posted: 3/18/2012 7:24:11 AM
invisiblejelly

Joined: 3/18/2012

Here is a picture of the etherwave standard board with the diodes in.

http://i298.photobucket.com/albums/mm270/michaelpudney/etherwavemodboard.jpg

C6 is replaced by 4 diodes 3 of which are IN 4148 signal diodes and one is a IN 4004 rectifier type.Three  4148's are connected to C6 and L12 and one 4004 and two 4148's are connected to D4 and L12...of course the correct polarity has to be done with these,the larger diodes show the correct polarities.Good luck if you try this.

Posted: 3/18/2012 7:59:53 AM
Thierry

From: Colmar, France

Joined: 12/31/2007

You could install the ESPE01 module instead. With that one you'd have the Double bass/Cello/Alto/Violin sound over more than 6 octaves. For that turn the waveform knob to about 10 o'clock and the brightness knob to about 3-4 o'clock once the module installed.

Posted: 3/18/2012 3:55:40 PM
Jeff S

From: N.E. Ohio

Joined: 2/14/2005

Not bad!  A little buzzy at the bottom though.  Is it my imagination, or does the sound get attenuated as the pitch increases (or did you play that way deliberately)?

Posted: 3/18/2012 8:25:04 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

invisiblejelly, you replaced for example C6, a 15pF capacitor by 4 diodes which are reverse biased by 12VDC, so they'll behave like 4 small capacitors in parallel. 3 of these are 1N4148 which will have a junction capacitance of 0.85pF each which makes 2.55pF. The 1N4004 will have around 12pF at this voltage which makes a total of 14.55pF, so you will be very close to the original capacitance of 15pF. Out of that these diodes will not act as diodes because they will be reversed-biased all the time. 

Thus I wonder what could make a difference there? Could you explain what was your intention and your computations when replacing the capacitors by diodes with obviously similar behavior, I'm sure I'm missing something! Could you please also post some screenshots from your oscilloscope so that we can get an idea of the pre- and post mixer waveforms?

Posted: 3/19/2012 6:54:02 AM
invisiblejelly

Joined: 3/18/2012

Hi Thierry I do have an ESPE01 module and I installed it ok and got some beautiful sounds and was able to get similar results that Thomos Grillo had in his great demo video on the module.But because I'm an experimenter and only have one EW theremin at the moment I took it out and found I could get a bass sound similar but not as good as the module by replacing C6 and C2 with two diodes( IN4004's) used as capacitors this proves that a diode is not the same as a capacitor of similar value.This started me on playing with diodes to see how it altered the sound by having mixed diodes in parralell as capacitors.Every diode I added altered the sound a little bit so I ended up taking out C6 (but leaving in C2) and I ended up adding 9 extra diodes till I got a sound I liked. I don't have an oscilloscope and actually only know a little bit about electronics only enough to do a bit of experimenting.I had fun with the diodes and got an interesting result over 4 and 1/2 octaves but I could extend that buy raising the wire to the pitch antenna more above the ground plate..but the bass was a little scratcy with this.I do prefer 4 and 1/2 octaves as it is easier to play tunes.

Posted: 3/19/2012 7:02:14 AM
invisiblejelly

Joined: 3/18/2012

RS Theremin I may have sqeezed one off trying to add some extra rich harmonics.I liked your cello sound and there are many theremin secrets to uncover it would seem so I won't ask of you privately how you did it so I can have the chance of hunting it down myself...what fun it is to experiment with theremins.

Posted: 3/19/2012 7:05:45 AM
invisiblejelly

Joined: 3/18/2012

And Jeff I did play the upper register a bit quieter and yes it is a little buzzy probablly from the diodes in paralell which might add some noise.I quite like the buzz.

Posted: 3/20/2012 8:30:18 AM
invisiblejelly

Joined: 3/18/2012

Thierry you wrote "You could install the ESPE01 module instead. With that one you'd have the Double bass/Cello/Alto/Violin sound over more than 6 octaves. For that turn the waveform knob to about 10 o'clock and the brightness knob to about 3-4 o'clock once the module installed."

Invisiblejelly says "For the cello sound with the diodes I have the brightness knob turned all the way to the right about 5 o'clock and the wave form at about 10 o'clock .

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