What is necessary to implement a volume antenna to this design? Is it a problem?
My New Year gift to TW: A new theremin circuit
No problem, you'd need a single volume oscillator working on a different frequency (to not to interfere with the pitch oscillators), a discriminator stage, a CV amplifier, and a VCA...
The thierrymin circuit is stable enough to work without external grounding, although the sensitivity of the pitch antenna might be slightly reduced. Switching from externally grounded to battery mode requires sometimes a slight retuning of the variable capacitor, though.
It works naturally best when grounded through the shielding of the audio cable if connected to a grounded instrument amplifier. - Thierry
Thierry, is there a particular reason why grounding through the shielding of the audio cable to the amp would be any better than a direct ground wire to an earth socket? Is it because the amp earth may be different to the mains socket earth (although it shouldn't be)?
I didn't say that "indirect" grounding via the audio cable shield was preferable over a direct earth connection. I wrote "It works naturally best when grounded through the shielding of the audio cable if connected to a grounded instrument amplifier." because that is normally the most common, the easiest, and the less risky way to ground a theremin.
Great circuit! I've built it on a circuit board and it worked perfectly fine! More stable on the circuit board than on a bread board indeed. Thanks so much!
However I'm now looking to make the instrument more bassy - something that would not be unlike a "bass theremin". Do you think that would be possible? I've read on this thread that the mixer had a 100 Hz hi-pass filter, I'll probably want to try to modify that later. But right now the main problem is that the lowest pitch generated by the circuit is still to high. Even if I tune the circuit at the lowest possible and mess around with the length on the antennas, I still only get about 0.5 inch of "usable" bass notes. I'd like it to be the bass instrument of the orchestra, so I'd need a wider usable bass range. Maybe that's just wishful thinking...
So I don't know much about the oscillators used here, but I'm wondering if you have any idea how to make them generate lower pitches. I'm trying to figure out the inner workings of the oscillators, but if you guys have pointers to what parts I'd need to change or look into, that would be great!
"I've read on this thread that the mixer had a 100 Hz hi-pass filter"
??? - the lower cut-off frequency of the mixer is 1.94Hz, thus that isn't the problem. To achieve a better bass register, there are theremins like the Moog Etherwave Standard or Plus, which can be upgraded with a special module to go down to 5Hz instead of ~60Hz by design.
But I fear that for this small and simple Thierrymin circuit here, there is not much which can be done to extend the low register. It has never been designed to replace professional instruments which cost a multiple... You might try (at your own risk ;) ) to replace C14 and C44 with 2.2pF instead of 3.3pF each. This should allow to go a little lower, but at the same time, the waveform would become somewhat smoother, so a good amplifier and speaker is needed behind.
Thanks for the super fast reply!
I'll definitely try that (at my own risk!) and report on the results. I know it's a big thing to ask for such a small circuit, but I'm still eager to try it!
So, I've changed the C14 and C44. It does help get the tone lower, and you were right saying that it needs more amplification. Also, I feel like it affects the range of the antenna, making it smaller. All in all, the tone doesn't get as low as I would have liked, but it was nice to try! Thanks again!
So right now, the best way to generate lower tones is to actually use an octaver pedal. It actually works pretty good. Sometimes, thinking outside of the box helps!
Still got a question though: would it be possible to extend the range of the antenna so it would be like 5 meters instead of a few feet? Or am I once more asking too much of such a small circuit? Thanks!