analogue ring modulator

[YAMI]

Hi guys, first post here.
So im about to do my first year project for my bachelor and i decided to make a case with 3 electromagnetic microphone inputs that can modulate each other in real time.
we have received fairly basic knowledge about this in our classes, but havent really expanded further on the topic other than making a basic board with oscilliators, an output and a volume know basically.
So we're supposed to make research on the thing we want to build which is what im trying to do here.
I would be really grateful if some people here could give a helping hand with the schematic itself. according to my teacher I was consulting last week, it should be possible to directly wire the inputs together to create a ring modulation effect. But since im not that hard on reading schematics yet, I can find out exactly how it would need to be wired together.
Hopefully I created this in the right place and I hope you have some insight on this topic since im pretty green on basic electronics.

[Leo_Gnardo]

according to my teacher I was consulting last week, it should be possible to directly wire the inputs together to create a ring modulation effect.

There we go with "theories" again... if mixing inputs caused a ring mod effect, that would cause ALL the mixes that have ever been made, live on-the-fly as well as recorded - to sound awfully weird. On the other hand, ring-mod-like effects can be created without any electrical inputs at all to a mixer. Too bad you can't get a front row seat at a concert by The Roches, you'd hear plenty of it. They don't often perform these days, but when they did, oh boy! Himalayan and Tuvan throat singers also carry it off, these days there's a couple of recordings you can find by overtone choir Prana, one is "Gathering In The Light" with Baird Hersey and Krishna Das, a good example of ear-busting modulations done "in the air", simply recorded for your listening pleasure & consternation. Listening on youtube, it's apparent the sound doesn't translate all that well: the modulations show up as distortion, but yet they are there. The sound is perfectly clear on their CD's. Recordings of vibraphone & marimba often display this type of modulation as well.

Another example is reflection of sound off a rotating moving surface, say bouncing sound waves off of fan blades, that gets a ring mod effect all right.

I'd say before reading schematics, maybe some reading up on Harald Bode, the father of the electronic ring modulator would be in order. He was a contemporary of Robert Moog and developed some instruments of his own. When I worked at the SUNY Albany electronic music lab, there was a Bode ring modulator atop the rack of Moog modules. It took a deft touch to use it well, as it could turn audio into annoying ear racket very easily. Those rare individuals who could use it well, got some amazing sounds in their compositions.

Perhaps your prof. is referring to the sum & difference frequencies that result from mixing audio signals, I guess that's a rough form of modulation, but hardly compares to the subtle through startling effects that can be accomplished with an electronic ring modulator.

[Enzo]

In fairness, he didn't say mixing inputs, he said wiring them together. I can imagine two voltage sources wired in series causing some intermodulation.

You should research how ring modulators function. If we suggest schematics, you still won;t know why our schematic works. If you can get two signal sources of any sort to modulate one enother, then adapting that to microphone or other audio sources won't be the maqin challenge.

[YAMI]

There we go with "theories" again... if mixing inputs caused a ring mod effect, that would cause ALL the mixes that have ever been made, live on-the-fly as well as recorded - to sound awfully weird. On the other hand, ring-mod-like effects can be created without any electrical inputs at all to a mixer. Too bad you can't get a front row seat at a concert by The Roches, you'd hear plenty of it. They don't often perform these days, but when they did, oh boy! Himalayan and Tuvan throat singers also carry it off, these days there's a couple of recordings you can find by overtone choir Prana, one is "Gathering In The Light" with Baird Hersey and Krishna Das, a good example of ear-busting modulations done "in the air", simply recorded for your listening pleasure & consternation. Listening on youtube, it's apparent the sound doesn't translate all that well: the modulations show up as distortion, but yet they are there. The sound is perfectly clear on their CD's. Recordings of vibraphone & marimba often display this type of modulation as well.

Another example is reflection of sound off a rotating moving surface, say bouncing sound waves off of fan blades, that gets a ring mod effect all right.

I'd say before reading schematics, maybe some reading up on Harald Bode, the father of the electronic ring modulator would be in order. He was a contemporary of Robert Moog and developed some instruments of his own. When I worked at the SUNY Albany electronic music lab, there was a Bode ring modulator atop the rack of Moog modules. It took a deft touch to use it well, as it could turn audio into annoying ear racket very easily. Those rare individuals who could use it well, got some amazing sounds in their compositions.

Perhaps your prof. is referring to the sum & difference frequencies that result from mixing audio signals, I guess that's a rough form of modulation, but hardly compares to the subtle through startling effects that can be accomplished with an electronic ring modulator.

ill look into that, thanks.
Hmm I guess it would be better to make a "main channel" and use the other 2 inputs as carriers?

[Mick Bailey]

There are a few 'classic' ring mod circuits - I've built several using transformers, but prefer the AD633 chip approach and this is what I've used in my latest synth build. The usual scenario is either a single audio source and variable (or even fixed) frequency oscillator, or two audio sources. Three interactive audio sources is an interesting challenge.

[Enzo]

What you haven't done, at least for us, is define what you want this thing to do. I mean "I want to make a ring modulator" is not very specific. Sorta like "I want to build a sound improver". SO to propose making one a main channel and so on still doesn't help us, so we cannot give meaningful help.

[eschertron]

In my limited understanding of a ring modulator, it is defined as a "four-quadrant multiplier", which in plain speak means that each of two signals is a carrier, and also a modulator for the other.
To get a feel (er, or rather, ear) for what ring modulation is, I imagine there are plenty of youtube examples (haven't looked). Plus, any decent digital recording rig has to have a plug-in or two for the effect. If you have access at home or school to such a setup, you can experiment and get an idea (or even a scope plot) of what ring modulation is. For example, a static carrier sounds much different than a complex signal, and could be easily mistaken for a simple tremolo effect (which is related, by the way, but not identical).

If the goal is to intermodulate not two, but three independent signals, some thought will need to be given on what that means. A product of the first two signals modulated by the third, perhaps? Was the 3 signals your idea or the profs?
If you go with something non-standard, the hard part of the engineering might be to decide on the implementation rather than the actual building/tweaking. As advised above by Mick, using an LM633 -- or any of the designs that feature OTAs like the CA3080 (yeah, my college textbook is that old) -- will make the transition into reality much smoother.
Good luck! Keep us posted, sounds like a fun project!

[rjb]

Greetings from a Kibitzing Bypasser

The first time I heard a ring modulator in action, I decided that if I ever heard one again it would be too soon.
I liked a lot of things Don Ellis did, but his intro to Hey Jude was not one of them.
Thus, I never bothered to investigate how RMs work.

Wikipedia tells me that a ring modulator (named for its ring of four diodes) multiplies two signals.
As noted, there are other ways of multiplying two signals; Googling "analog multiplier" shows a bunch of methods.

Ring modulators frequency mix or heterodyne two waveforms, and output the sum and difference of the frequencies present in each waveform. Multiplication in the time domain is the dual of convolution in the frequency domain, so the output waveform contains the sum and difference of the input spectral components. For the basic case where two sine waves of frequencies f_carrier and f_voice are multiplied, two new sine waves are created, one at f_carrier +f_voice and the other at f_carrier - f_voice.

https://en.wikipedia.org/wiki/Ring_modulator
https://en.wikipedia.org/wiki/Ring_modulation

So, you typically have two inputs. If you feed a musical instrument into one input and some random frequency into the other, you'll probably get random dissonance out. If you feed a single instrument into both inputs, or two different instruments playing in unison into the two inputs, I imagine you may produce some interesting tone colors.

This commercial demo shows that you can get musically interesting output by feeding an oscillator at a frequency related to the music (say the root or fifth of the key of the tune) into the "carrier" input.
https://www.youtube.com/watch?v=cjzXb0CdSUs

I'm not sure what you want to do with three microphone inputs.
Can you explain further (or maybe revise your project concept)?

--------------------------------------------------

Himalayan and Tuvan throat singers also carry it off,

I learned how to get the easiest overtone series at a percussion workshop.*
Sing "Herrrr" at a low pitch, then gradually shift mouth & throat position to "eeee".
At some intermediate position, you'll feel and hear various overtones popping out.
You can shift back and forth, making a sound like an electric razor or hair trimmer with a mis-adjusted blade.
If you live in an apartment or rowhouse, it's a great way to endear yourself to the neighbors.

* Percussion WS connection: Sing your low note to match the BMF tuned frame drum; the drum masks your fundamental note, making it sound like you're singing only the overtones.

[Mick Bailey]

A ring modulator as defined cannot operate on three signals. You can mix signals, but those mixed signals won't modulate each other. Another consideration is that a ringmod has the carrier nulled - it does not appear at the output unless the circuit is imperfect or badly designed. Because of the multiplication, the absence of a signal at either the main or carrier inputs will result in zero output.

There are a few approaches you could take, but it depends what the purpose of the circuit is. You can string ringmod circuits together in series, that way any input will modulate the others, but the output could end up as mush. You can work out mathematically what the outputs could be.

As it stands there's too much latitude in your spec - narrow down the purpose as per Enzo's post, and list the must-have critical features of the circuit. My approach is always to do a block diagram that identifies each functional unit and signal paths. It's then easier to design the circuit at each individual stage.

[YAMI]

thanks for the comments guys, it gave me a much more clear image of what I wanted to do and sorry for my somewhat vague description in the first post.
The important thing to remember here is that we're novices when it comes to this and our teachers are aware of that, so its mostly for experiemental purposes. Its gonna be used as an experiment more so than an actual "instrument" or effect.
So the device is a case that on the front consists of 3 electromagnetic mics where you can put different electronic devices on thus using those signals as the audio source.
in my mind, there's 9 knobs on the box as well. 3 volume knobs for each input and the other six knobs controls how much each source modulate eachother.

[Jazz P Bass]

Just a thought: Quote"im pretty green on basic electronics."

Why not start off with something a tad less complicated.

[rjb]

sorry for my somewhat vague description in the first post.

I'm still lost.

its mostly for experiemental purposes. Its gonna be used as an experiment more so than an actual "instrument" or effect.

OK, then what's your experiment? Maybe hook up 3 function generators to the inputs and scope the output?

So the device is a case that on the front consists of 3 electromagnetic mics where you can put different electronic devices on thus using those signals as the audio source.

What does this mean? Please name some "different electronic devices". How are they going to interface with your box?

in my mind, there's 9 knobs on the box as well. 3 volume knobs for each input and the other six knobs controls how much each source modulate each other.

How about just the volume knobs? Or, if your inputs are from devices with adjustable outputs, no knobs?
I would take Mick's advice and draw block diagrams with signal flow from inputs, through the potentiometers (I assume the knobs are attached to pots) to outputs.
Just how is that control matrix going to be configured?

I think you meant to label the knob at 3rd row, 2nd column "Modulation from C".
But more importantly, where is/are the output(s)?


PS- In my previous post, I failed to note that commercial ring modulators used for musical applications typically mix the "dry" signal with the modulated output.

EDIT: I agree with Jazz. Scale way back. Not to be snarky, but it seems you don't know enough yet to know what you don't know. Maybe try using the schematic from Wikipedia as the basis of a standard 2-input ring modulator. You would still have the engineering problems of sourcing parts and interfacing the box to real world devices. And you might want to mix the "dry" input with the modulated output. That would be more than enough of a challenge for a first year project! IMHO.

[YAMI]

Hey guys, thank you so much for your very valuable output. because of your replies I was able to get a really clear image of what I wanna do.
Im gonna make a ring module with the D633 IC with 2 coil microphones. And the schematic is kinda easy, but ill reply again if I need any assistance.
Again, thank you for setting me on the right path.

[Mark Hammer]

I think one needs to distinguish between what counts as a true ring modulator, according to a classic electronic definition, and what sounds like a ring modulator.

Just about any periodic modulation that occurs in the audio range (as opposed to subaudio) can produce audible sideband products that sound for all the world like a true ring modulator. So, take a tremolo, a vibrato, a phase-shifter, a flanger, a chorus, a swept filter of some kind, and modulate any of them faster than 20hz or so, and they will instantly acquire that "rubber band" quality. What I find fascinating is the manner in which they can each sound so different to us, when modulated at subaudio rates, yet begin to sound so similar as modulation rate goes up. I'll wager that if I set the LFO for 100hz, you wouldn't be able to tell any of them apart.

Not that they turn into the same thing. Rather, it's a matter of what features of the resulting sound we attend to and perceive most.

[rjb]

Im gonna make a ring module with the D633 IC

I think you mean AD633.
Google tells me AD633 is an Analog Devices quad multiplier; D633 is either a Darlington transistor or a Moog direct drive servo valve.

with 2 coil microphones.

What are "coil microphones"? Induction loops? Moving-coil (AKA dynamic) microphones?
What are your anticipated signal sources?

PS- Thanks for starting the ring modulator thread. I really needed another item on my "maybe some day" hobby project list- to be started after the home repair project list!