Voltage Controlled OpAmp RingMod (Modulator)

[fonik]

harry bissell once recommended irvine's design for a ring mod. i changed the resistors to our common values, and added two VCAs to the inputs, thus giving a voltage controlled ring mod. makes a lot of fun.
refer to this thread for comments, samples and such...

there is enough interest for me to offer a professional built PCB for this project, and i am asking for advance-orders right now.
however, i won't take any money before i hold the PCBs in my hands.
the PCB will be 2.3 x 2.8 in in size. if hit the 50pcs the prize will be about 7.-USD/5.50EUR ea.
i would believe the difficulty level of this project is intermediate. to calibrate the VCAs a scope would be most helpful.
regard the Recommendations for PCB sales on electro-music.com, please.

SOLD OUT (edit: 1 DEC 2010)

the pricing:

PCB:
7.- USD / 5.50 EUR

P&P:
Deutschland: 1.50 EUR
Europe: 3.50 EUR
Worldwide: 6.- USD (1 PCB) / 8.- USD (1+ PCBs)

Documentation
VCRingMod building docs

a finished module could look like this:


or like this (right part of the triple module)


here's my schematic:


original post:
harry bissell once recommended this design for a ring mod. i built it on breadboard, changed the resistors to our common values, and added two VCAs to the inputs, thus giving a voltage controlled ring mod.
i had to remove it from breadboard, but i will built a module soon. so again, no soundclips for now. however, you could easily build it on your breadboard very fast. i just wanted to share, since i liked it very much.

Reference: Irvine, Robert G., Operational Amplifier Characteristics and Applications, p. 174-176

[kkissinger]

Forgive me if I sound like a total newb, but I'm trying to figure out the meaning of the op amp symbols at 10-9 and 7-8 ... are they just unity-gain buffers?

Also, at the IC1A and IC1B inputs, I presume the diodes are external, correct?

The voltage-control biases the modulator, correct?

Thanks!

[blue hell]

[kkissinger]

Hey, BlueHell, thanks for the info.

Incidentally, I just added a switch and a couple of capacitors to my Aries Balanced Modulator (to get rid of unwanted DC bias) and this circuit caught my eye -- looks like a neat way to get some clean modulation.

I just glanced at a recent parts order (I should take delivery tomorrow). I'm building a couple of MPS modules that use the LM13700 and I ordered 10 chips to build up my parts stock. I'll be set to mess around with this circuit

[fonik]

[slacker]

Thanks for sharing this Matthias, it's very cool.

I've only breadboarded the modulator part without the VCAs but it works really well. You get really nice ringmod sounds with 2 audio signals and I like the fact that you can drop the carrier right down to below audio and it acts like a VCA.

[fonik]

[fluxmonkey]

just straight (w/out the VCA modulation), how does the sound of this compare to other ring-mod designs, like 633 or even passive transformer/diode?

[widdly]

Does the ring mod work with DC inputs and AC inputs?

If it works as a VCA with a DC input, you couldd loose the 13700 and duplicate the ring mod part twice for the left hand side VCA's. Then it could also work as a 4 input ring mod.

[fonik]

yes. it works DC. great idea, widdly.

as in comparison to other ringmods: i have a AD633 ringmod, i will be able to compare them as soon as i built a module from our new circuit.

[BOB-SNARE]

[slacker]

Here's a couple of quick soundclip of the modulator, I haven't made any attempt to do anything musical, it's just to show what it sounds like.

One input's a fixed frequency saw and the other is a triangle that sweeps from below audio and back again, in the second clip I change this to a saw half way through.

If you look at the wave form you can see that it works how BOB-SNARE explained. At slow modulation speeds the ramp up saw morphs into a triangle and then into a ramp down saw. If you use a triangle wave it morphs into one twice the frequency.

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ringmod1.mp3
Description:		Download (listen)
Filename:	ringmod1.mp3
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ringmod2.mp3
Description:		Download (listen)
Filename:	ringmod2.mp3
Filesize:	1.25 MB
Downloaded:	1768 Time(s)

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[fonik]

PCB could look like this. however, i will have to build my SMT version first. so stay tuned...

[LektroiD]

I need 4 of these! I love this effect. I also have the Moogerfooger MF102.

Would this also have low & high impedance to work with mic, guitar or line level (presuming this is the purpose of the VCA), or would I need to modify?

[fonik]

[richardc64]

[fonik]

wouldn't we need two actually? one for the carrier and one for the modulator?
anyways, i'd liked to leave it as a synth module. maybe i should/could bring out the left opamps pins to pads? the one could use it for whatever he wants to...

BTW i once had the MS20 external in circuitry on my breadboard and i found it quite useful. i especially liked the idea of using a 1M potentiometer to change input impedance and amplification. worked fine for me.

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[a100user]

Hi Matthias,

Bringing the pins out to pads is a very good idea.

Thanks for posting the MS20 circuit, agree that could be very useful.

David

[Dave Kendall]

+1 for pads for the spare Opamp.

Maybe if board space permits, include pads for the couple of additional components to make a simple attenuverter?
They're always useful to have around....

cheers,
Dave

[richardc64]

[fonik]

[fonik]

built the SMT version tonight. worked from the start. sound samples will follow as soon as i got the frontpanel and put it into the system. BTW, i enjoy SMT more and more...

[haxster]

Very nice Design. I love no Wires! what kind of Jacks are those? Are those BI potentiometers also?

[fonik]

jack sockets are from china (chuangjiebao), potentiometers from taiwan (song huei). both direct orders from manufacturer (MOQ 1000psc).

[adambee7]

Another excellent piece of work Matthias. When you get either version ready for sale I'll have 4. Cool.