Joined: May 16, 2005 Posts: 8933 Location: Birmingham, England, UK
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Posted: Tue Jul 06, 2010 1:36 am Post subject:
Ondes Martenot Schematic
Well, not quite.....
But I knew it would get your attention!
This, is the schematic from an RCA Theremin. The Ondes is very similar, except the frequency is either swept by a Variable Capacitor or potentiometer. Has anyone got any ideas how a circuit like this one could be modified so that pitch and volume isn't swept or changed by body proximity, and could be changed via a VC or Pot?
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Joined: Dec 29, 2006 Posts: 1176 Location: australia
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Posted: Tue Jul 06, 2010 3:51 am Post subject:
not quite the same but a couple of versions of a simple tube based instrument.
one from Judd's book, other from Douglas
both have vibrato and operated by keys......relays?
Judd tone source.jpg
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Joined: May 16, 2005 Posts: 8933 Location: Birmingham, England, UK
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Posted: Tue Jul 06, 2010 4:10 am Post subject:
Thanks Andrew, but it doesn't quite address the question, because for one, that circuit is a multivibrator, which produces a square wave (not the tone I am looking for). I've got an excellent book by some guy (I think it may also be a title by Douglas- but much older, called "An Electronic Organ for the home constructor" which has the Ondioline oscillator in it, but yet again, it's a multivibrator example. There is also of course Eric Barbour's example which produces a sawtooth, but both of these are not heterodyning designs, and it is this design that produces such a nice tone (or as far as I can work out).
I found a brilliant Australian website a couple of years back, with an example of a heterodyning sweep test oscillator- that worked at audio frequency. The bloke who owned the site, an academic, said he'd get back, but he never did, even after I tried to recontact him. I've probably still got the pdf- but where is another question! _________________ ACHTUNG!
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v-un-v - what basic waveform are you looking for? Seems to me that two HF sine wave oscillators (one fixed, one variable) fed into a diode ring mod should give you heterodyne frequencies in the audio range. Of course the upper sideband will interfere with your neighbours' TVs but they'll just have to suffer for your art). It would be interesting to have a variable waveform on the fixed oscillator, perhaps with some expressive controller.
Veering slightly off-topic, how nice to see a mention of Fred Judd. Just thinking of the flexi-disc he recorded for Practical Electronics still makes me smile after all these years.
And... since you have the Alan Douglas and Judd books - I remember seeing in (I think) an Alan Douglas book, an obsolete continuous pitch controller instrument that somehow used a metal mesh cylinder wrapped around a resistive element. It's killing me that I can't remember where as I really want to build something like this, and it would be great for an Ondes-like device.
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Posted: Tue Jul 06, 2010 4:06 pm Post subject:
Wouldn't a ring mod just produce a sum and difference of the two frequencies it was fed with, resulting in not such a nice sound? (I'm ring-modulated up to the eyeballs right now- but that's another story! )
This is the sound that I'm looking for;
The sound is very 'woody'. Almost hollow in nature. Could be a square but not quite. _________________ ACHTUNG!
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Posted: Tue Jul 06, 2010 4:17 pm Post subject:
I found this too the other day. The 'synth' is a 1930's Hammond Novachord!!!!!!!!!!!!!!!!!!! WOW!!!
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Posted: Tue Jul 06, 2010 4:39 pm Post subject:
slabman wrote:
And... since you have the Alan Douglas and Judd books - I remember seeing in (I think) an Alan Douglas book, an obsolete continuous pitch controller instrument that somehow used a metal mesh cylinder wrapped around a resistive element. It's killing me that I can't remember where as I really want to build something like this, and it would be great for an Ondes-like device.
I have access to both of Douglas's books, will scan the relevant pages if you like.
just to throw another one in the mix, I have been experimenting with 6BN6 & 6JH8 tubes as demodulators. It seems neon oscillators produce sine waves when pushed (20kHz), so i tried to use one as a fixed oscillator and another as variable, kind of a BFO. Found (and was warned) that neons get pretty unhappy at 20kHz and the signal amplitude gets very small (~2V in my case).
So will go back to trying a simple triode-based MV as the fixed oscillator and one of the circuits above as the variable (thyratrons are also not too keen to operate at 20kHz)
v-un-v "Wouldn't a ring mod just produce a sum and difference of the two frequencies it was fed with". Exactly. So, if you had a 100khz fixed oscillator and another that varied from 100-120khz, the lower sideband would be 0-20khz and the upper is in the RF range and easily filtered out. So the result is a variable pitch and not the familiar klang produced when carrier and modulator are both in the audio range.
AndewF - is that means I didn't dream that controller, then yes, please scan those pages in. I was beginning to think a synth from a parallel universe had impinged on my subconscious.
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Posted: Wed Jul 07, 2010 5:46 am Post subject:
You are right- and I am a fool!
THX
It would be interesting what this would sound like, but in the meantime, I must go out now.
l8r.
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Posted: Wed Jul 07, 2010 8:05 am Post subject:
RF wrote:
you were looking for that special sweet creamy tubey goodness...
Oh yes! Where? I WANT!
I just love the idea that it is so pure and simple. The controller being the most important element, because after all, this is an instrument that must be played! _________________ ACHTUNG!
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Joined: Dec 29, 2006 Posts: 1176 Location: australia
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Posted: Fri Jul 09, 2010 12:54 am Post subject:
slabman wrote:
And... since you have the Alan Douglas and Judd books - I remember seeing in (I think) an Alan Douglas book, an obsolete continuous pitch controller instrument that somehow used a metal mesh cylinder wrapped around a resistive element. It's killing me that I can't remember where as I really want to build something like this, and it would be great for an Ondes-like device.
now I have scanned it an read the article more closely, maybe this isn't what you are referring to. nevertheless the Diakon cylinder on pg63 looks like an excellent project
Thanks for those scans - you're right that it's not the object I am (mis?)remembering but it's still marvellous to see these. Those early synth pioneers were wonderfully inventive. To this day, nobody has picked up on things like the waveform controller in the Electronic Sackbut (I seem to remember that appears in the Douglas book too).
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