Gordon's Progress

On the topic of Modular Synthesizers - I just purchased one from Analogue Solutions. Or rather, two "MiniModulars" which I proceeded to make into a quad-oscillator, dual filter audio damage machine.

Rather than buying a signal processing machine, I would buy a "system" modular synth, which you can actually play regular notes on, for timbral and tonal variation. It's nice to "not" use the same timbre to process into a new sound.

Also, when getting into modular synthesis, take the time to listen to as many samples of said system as you can find. This is the reason I chose Analogue Solutions over Doepfer. Roughly, their cost is the same, and in my ears, the AS sounds fuller. It could also be that I am a drummer, and probably a little deaf! :)

AS systems are compatible with Doepfer and Analogue Systems modules.

Other suggestions: For a more "unique" sound when it comes to synthesis, try steering away from your standard Moog filter sound. Yeah, 24dB filters are great, I know, I have two! :) But your synth will be able to realize so much more with a few different filters. the MS20 clones are HUGE nowadays, and Doepfer is making vactrol filters that supposedly sound "creamier" than your standard filter. Mainly to do with an enclosed LED. When it comes down to controlling your analogue synth, you will definitely need a MIDI-CV controller. It's absolutely necessary for doing more than drones.

I've been reading your progress reports, and am still way back at page 7. I like your "elastic chest hair" idea!

My final suggestion - although digital effects are definitely on the less expensive side, especially when you want the most quantity for your currency - in the long run, you will be more pleased when you buy boutique analogue pieces. It guarantees a tailored sound, custom built to your preferences. That's a whopper of a discussion, though...

Thanks for your informative posts!

[i]Rather than buying a signal processing machine, I would buy a "system" modular synth, which you can actually play regular notes on, for timbral and tonal variation. It's nice to "not" use the same timbre to process into a new sound.[/i]

Good point. Just go with a well-equipped synth. You'll have a lot more possibilities and fun with it!

The real issue is how to interface your Theremin with the synth.

Indeed, to utilize an analog synth from any MIDI-equipment (computers, keyboards, or a MIDI-theremin) then you would need a MIDI-cv converter.(I own the one from PAIA and it is very good.)

Alas, your Kees isn't MIDI or CV equipped.

If you are into kit building, you might consider a Paia Theremax -- besides the standard pitch and volume CV's it also has gate, trigger, and velocity CV's.

One of my future projects is to build the Paia "MIDI Brain" that converts cv's to MIDI -- the idea being that I can control MIDI equipment from my Theremins.

The only MIDI theremin that has gotten rave reviews is the Moog Ethervox (out of production and costs around $5000 if you can find one!). Reviews on other MIDI theremins are sketchy.

The Doepfer Theremin module is a single antenna unit -- the antenna is right there on the control panel, and would be tough to adjust controls without also getting into the control zone of the module. I wouldn't dissuade you from getting the module however you may find it limited compared to your Kees.

Kirk, welcome to Thereminworld. Enjoy!

-- Kevin

Also at issue is what any given MIDI Theremin or MIDI converter can actually do - what features does it offer? what tricks can you do with it? Even the fabled Ethervox - what can it do with MIDI? Peter Pringle has given us some brief descriptions and demos, but I still don't feel that I have an adequate understanding of what it was able to do.

I have a list of features I think a MIDI Theremin should have, some of which I know the Ethervox had, some of which I'm sure no MIDI Theremin has had, many of which I have no idea if any MIDI Theremin has had. I consequently don't know which features I should turn into software and release for free, which I might have to get Moog Music's permission for first, and which I should patent first.

Doepfer is releasing eventually a "Pitch to CV" converter module

Hi Kirk, welcome to Theremin World, and in particular the strange world of Gordon's head. :-)

And thanks to everyone who has pitched in with synth knowledge.

I'm pleased to hear that modules from doepfer and analogue solutions are compatible. I take it there is a well defined standard for CV and manufacturers stick to it? I'm also pleased that AS are UK based. I like dealing with local companies.

Doepfer appeals to me because the feeling I got from the website is that Herr Doepfer thinks the same way I do about that sort of thing. In fact they way I found the site was by figuring out how I would process the signals coming from a theremin if I had to make the hardware myself, and then searching for a manufacturer that had already done it for me.

With regards to CV or midi - I get that midi is far more sophisticated, but it comes with a price. Complexity. It is primarily designed for fixed-pitch instruments, so any pitch data generated by a continuously variable instrument like a theremin is going to have to be represented by both pitch and pitch-bend data, which is a compromise - it sounds like setting yourself up for confusion and head-scratching later on. The simple, direct, one-to-one relationship between pitch and a control voltage has to be a lot simpler to deal with.

I also have a lot of experience with a system that is in many ways analogous to a modular analogue synth, namely the programming language Forth, so I have a strong starting point to build on, and appreciate the power of such a system to achieve one's goals quickly and easily, given the right mindset.

By contrast, everything I see about midi just looks like a confusing, cack-handed way of going about things. A real hotch-potch. But then I think the same of a lot of conventional programming languages too.

With regard to discrete modules vs. an all-in-one solution, I would go for modules. The plan would be to start with the bare minimum, which would be two antenna providing cv out, controlling an oscillator and an amp respectively.

My options for antenna are

- the doepfer modules, the cheapest solution, but nowhere near my requirements.

- an ePro, which certainly has the pitch antenna I want, although it sounds like the volume would need the de-snappify mod, the most expensive solution, with the bonus that I get to own an ePro, but beyond my means.

- a theremax, I am not safe with a soldering iron and I have a recollection of reading that it was not the most linear of theremins.

- custom built antenna similar to the doepfer modules but built to a better specification and freestanding. Most likely beyond my means, unless I can persuade someone that it's a commercially viable product; Herr Doepfer is not convinced and doesn't do one-offs. Nonetheless this is my ideal solution, and Mr Rothman at theremin.co.uk does do custom jobs, and there will be an opportunity for me to talk to him face to face next year, so I'll be deferring any decision until after that.

- an etherwave and a pitch to CV convertor. The most practical solution and my fallback option, although it still strikes me as silly to go to the trouble of creating a pitch only to reduce it to a couple of control voltages. Far better to go directly for the CV. Again, expense is an issue - a lot of the cost of Mr Rothman's device is probably in its midi capabilities, which I do not want. I am hopeful that Herr Doepfer's pitch to cv module gets built sooner than eventually, and that it is up to the task at a more affordable cost.

After that, I would want to build it up slowly, adding one or two modules at a time, taking my time to explore the capabilities of each one as I get them, and figuring out carefully what module I would add next.

Perhaps I could best describe my long term plan like this. I want to design a sort of über-theremin, which is to an etherwave as a church organ is to a piano, and this i

[i]"an etherwave and a pitch to CV convertor. The most practical solution and my fallback option, although it still strikes me as silly to go to the trouble of creating a pitch only to reduce it to a couple of control voltages. Far better to go directly for the CV."[/i]

Just to clarify: a pitch-to-cv converter will produce a control voltage given any monophonic input -- you wouldn't have to purchase an additional Theremin. Your Kees would work fine.

Theremins produce a pitch internally and then that pitch is converted to a cv. It is the same process whether the Theremin has it's own pitch-to-cv circuit or if you use an external module.

Midi note-on/note-off messsages are biased towards keyboard instruments. Midi Theremins generally transmit continuous controller (CC) messages such as pitch-bend data. Software can be used to map (or quantize) the pitch-bend data into discreet notes if that is what you want. (the Ethervox does this in firmware and, as such, can be played like an aerial autoharp).

If you wish to control an analog modular synth from a Theremin there is no need for MIDI because you can control your synth directly from the analog control voltages.

The standard for most synths is 1volt per octave. (that is, the oscillators and filters contain linear to exponential converters). To play a synth so that it tracks in tune with your Theremin, your synth should have 1volt per Octave response.

Gordon, having read your posts and listened to your music I think a modular patchcord synth is the way to go for you. There is nothing that encourages experimentation like all the knobs and patch points on a modular synth. Though digital synthesis offers wide capabilities analog synth programming is more intuitive and spontaneous.

You are really in for a lot of fun, Gordon.

I have faced my fear of circuit diagrams and found one of a theremin here (http://www.physics.gla.ac.uk/~kskeldon/PubSci/exhibits/E9/cir1.gif).

[edit] - or I could have just waited to read what Kevin posted while I was writing this posting (which took about an hour and a half as I was figuring it all out as I went along.) D'oh. [/edit]

Now, do I understand it correctly?

Looking at the top half, the pitch control circuitry, I see two high frequency oscillators, both identical except that one has an antenna added in. They are connected by a device which has two coils and a ring of diodes. This must be the ring modulator that heterodynes the two signals to produce an audio output. So if one were to build that half of the circuit one would have a pitch only theremin.

Looking at the bottom half, the volume control circuitry, I see an exact copy of the pitch control circuitry, and below that an operational amplifier and a bunch of resistors and stuff, (including another ring of diodes) that takes feeds from the volume control circuitry and the identical portion of the volume control circuitry and somehow or other uses the output from the upper half of the volume control circuit, which is pitch information, to vary the volume of the output from the pitch control circuitry.

Gosh. I had imagined the volume control would be a lot simpler than the pitch control. Do all pitch and volume theremins work like that, or is this atypical?

Also, is it the amplifier portion of the circuitry that determines the responsiveness of the volume antenna, or is the shape of the antenna the determining factor? Well, the shape of both antenna are the same on my Kees as on an etherwave, but they have quite different volume responsivenesses (is that a word?) and as a check I have just been and swapped the antenna of my Kees over. After retuning it appears the shape of the antenna is not very significant. (But by golly it looks weird with the antennae in the wrong places.)

So what have I learned?

Unless the circuit I looked at is very weird for a theremin, a pitch and volume theremin is basically two pitch-only theremins joined together. How they are connected determines the behaviour of the volume antenna. So my idea for a volume only theremin or a theremin that creates a control voltage directly are both a bit silly.

Also the pitch to CV converter, an envelope follower (i.e. a volume to CV converter, yes?), a couple of CVOs, a ring mod and an etherwave is looking more like the preferred starting point for my übertheremin, seeing as I am already familiar with the response of the pitch antenna (as it is similar to my Kees) and I liked the volume antenna when I used it at my gig. Now all I have to figure out is which order to buy them in...

Gordon, while you posted your last message I edited the one before and added a little info.

Ironically, the volume side of the Theremin circuit is a little more complicated than the pitch side.

The pitch side is pretty simple, as you said, just combine the fixed and variable oscillators to get the beat frequency and that is that.

The volume side must somehow take its beat frequency and convert it to a signal that can be used to control volume. In the Theremax, the volume beat frequency is run through a pitch-to-cv converter and the resulting cv is used to control an internal Voltage-controlled Amplifier (VCA).

[i]Also the pitch to CV converter, an envelope follower (i.e. a volume to CV converter, yes?), a couple of CVOs, a ring mod and an etherwave is looking more like the preferred starting point for my übertheremin, seeing as I am already familiar with the response of the pitch antenna (as it is similar to my Kees) and I liked the volume antenna when I used it at my gig. Now all I have to figure out is which order to buy them in...[/i]

You are on the right track, Gordon. Chances are, a pitch-to-cv module will include an envelope follower (and yes, an envelope follower is a volume (amplitude) to cv converter.) You would use your control voltages to control any modules that are voltage-controllable (usually prefixed with the letters "VC"). The most common modules are VCO (Oscillator), VCF (Filter), VCA (Amplifier). Most modern analog synths have many more functions that are voltage controlled.

Often the Low Frequency Oscillators (LFO's) are voltage-controllable, too. Thus, you could use your Theremin to control modulation rates, or the clock speed for sequencer modules.

A modular synth is, well... pretty personal. Those of us who have assembled them have chosen modules that fit our particular needs.

Having said that, your "barebones" modules (for starters) would be a case, power supply, pitch-to-cv converter/envelope follower, two or more VCOs, a VCF, a VCA, a noise generator, Sample/Hold, Ring Modulator, and a couple of Envelope Generators (EGs) to control the others, and LFO's to modulate everything else AND to trigger the EGs. Your upgrade path could include a fixed filter bank, sequencer(s), and more VCOs, VCAs, and VCFs. You will also need mixer modules, too.

For grins, you can check out my website http://kevinkissinger.com -- click on the "Synthesizers" link and you will find the specs for my modular synth.

Very exciting project, Gordon!

One more idea =
Frostwave is offering a theremin that not only outputs sound, but Pitch CV and Gate as well. So, you could have a theremin that puts out control voltage. It is not too expensive - I almost bought it, instead of the Etherwave.

As for boutique pieces - there are several companies that produce effects/synths/etc. that are not typical. Frostwave, for example is considered "boutique". Not common. Most people do not have Frostwave effects.

A modular synth is considered boutique as well. Most people go to their local music store, buy the first keyboard brand name they see. Most are looking for the most "bang for their buck", so to speak. A Theremin is boutique. Not too many people have them. They are made in small numbers.

Here are some really neato manufacturers, Google their names:

Frostwave
4ms
Z-Vex

And some less than boutique, but still fairly unique:
electro-harmonix
analogue solutions
analogue systems

Lots of great gear, slightly more costly, but completely unique sound - and don't let me get started on amplifiers...If I was a guitarist...I would probably have the debtors after me.

Thank you Kirk. I understand now. It's the guy with a dusty little shop who really knows his stuff and that people go to when they actually know what they want and want to talk technical without being stared at as if they have a duck on their head by an assistant who is at best vaguely aware of the names of some of the products on offer.

Kevin. Your bare bones system has given me quite a lot to think about. I can already see a lot of interesting possibilities of things to do with the list of modules you suggested. You have also given me plenty of things to read up about until I am in a position where I can say, of all these possibilities, which is the one effect that will require only a couple of modules and that will keep me amused for long enough to save up for the next couple of modules which will allow me to start playing mix 'n' match with the patch cords and start realising the potential of a modular system.