how do different wave-forms used as the fixed pitch osc affect the tone?

thanks fred and don for all of your responses- i have to say i am really impressed by the level of expertise on this forum - and i can only imagine what would have happened to my sanity if i had sacrificed an etherwave board and countless hours to perform a mod on the fixed pitch oscillator that would have produced no real difference in sound!!!

with regard to modding both the fixed and variable oscillators, i think i'll have to leave that to the pros - fred, did you say somewhere that your new theremin is in the "latter stages" of completion? i think once it is finished it would really set a new waypoint in the history of the theremin's development!

One quick and dirty thing to try for bipolar transistor local oscillators is to tweak the bias point.

Dead-center of the rail voltage will be about as close to a sinewave as you can get. Dropping the bias down with a voltage divider will allow you to distort the local oscillator waveshape. But this affects other things, like voltage gain, collector-base capacitance, etc. So you may have to do a bit of re-tuning when you change the bias.

Don

[b]"fred, did you say somewhere that your new theremin is in the "latter stages" of completion?"[/b]

I probably did ;) ... And, yes, I have more than one Theremin in the "latter stages" - I think I have some deep personality problem which seems to prevent me from moving out of "latter stages" to "in production"! --- It goes something like this.. At the "latter stage" I have found better ways of implementing what needs to be done, see 'features' which can 'easily' be added, find some problems which are 'minor' but need fixing, and also need to refine the design to eliminate the plethora of trimmers etc tacked on to the prototype, in order to make the product manufacturable.... So I do a redesign incorperating these - get to the "latter stage" of this, and find myself going full circle. As much as anything, it is lack of dicipline on my part... And also a somewhat (perhaps) unrealistic demand I impose on myself that what I put on the market must be damn near perfect, and (above everything else) absolutely reliable..

But I will have a damn good Theremin on the market soon - I do not want to say anything more about it though.. When I announce it, there will be a U-Tube video and units in the post to people who will test it.. Hopefully I should have the needed funds to start production in May / June this year.

[b] More on EW tone .. [/b]
As Don says, you can distort the local oscillator waveshape.. and there are sufficient harmonics in the other waveform for this to make a difference.. However, The bigger problem with the EW is (in my opinion) not that there are too few harmonics, but that there is too much distortion... I do not own a EW, but have built the circuits and played with them - It is my belief that the diode mixer and following VCA with its nasty distortion control which spoils this instrument.
Remove the diode mixer and replace it with a AD633, and remove the horrible VCA and replace it with something like a THATS 2180A, and you get rid of the real problem.. Then simply square up the output of variable oscillator, square up the reference oscillator and add a simple tunable RC lowpass filter for tone control, and I believe you would have a far better instrument - But the above have not been tested on a real EW.. One day I will buy an EW and see if this works! ;0

[i]However, The bigger problem with the EW is (in my opinion) not that there are too few harmonics, but that there is too much distortion... [/i]

hmm, that is an important point - the input signal on the etherwave is set to overload the [edit - amp chip? i forget] and clip the sound (the instructions say this turns the 'skewed sine' into a square wave)... so this probably means that significant work on feeding different waveforms into the RF pitch oscillation end would probably just sound like changes in pulse-width unless the clipping were remedied as well, right?

[i]"so this probably means that significant work on feeding different waveforms into the RF pitch oscillation end would probably just sound like changes in pulse-width unless the clipping were remedied as well, right?"[/i]

Not sure what it will sound like.. but I am of the opinion that there is little point doing much at the HF front end if the mixer / distortion / vca is left original..
This discussion got me thinking about how one could do a practical mod build for the EW.. I think perhaps the best way would be to buffer both HF waveforms (high frequency unity gain buffers - perhaps even video amplifiers and 75 ohm co-ax cables), and take these together with the volume CV to a connector (Perhaps a S-Video connector).. One could then process these waveforms in an external box (having waveshaping,mixer+VCA).. This would leave you with the original EW functioning as normal, and allow the box to give another audio output with good harmonic control and without the horrible EW distortion - One could mix the audio outputs to taste.