PWM Resistance Ring Mod/Ramp Trem **Audio Samples Included**

[Transmogrifox]

I have been experimenting lately, and I have come to thoroughly enjoy the ring modulator.  I suspect they arent' currently popular with guitar because they're a bit weird for modern pop--but at least Radiohead uses them.

Here's the "conceptual schematic":

http://putfile.com/pic.php?pic=10/2942051539.jpg&s=x10

This schematic shows the guts of the unit's operation, but the extra interface pots and level-shifting and trimming I did on the circuit that I made the audio clips with is not shown because it's currently pretty hodge-podge.  I intend to finish cleaning up this design and then I'll see if I can make a good useable pedal out of it.

Here are some audio demos of some of the sounds I am able to achieve with the above circuit:

http://media.putfile.com/RingFun1
http://media.putfile.com/RingFun2
--Just a bunch of messing around and tweaking knobs.  One thing to make notice about is the carrier oscillator frequency range when tweaking the knob.

http://media.putfile.com/TremDelayNoFX
Not a punk song or anything to do with NOFX.  This is straight from the breadboard to the audiocard, so the only effect is the Ramp Trem.

http://media.putfile.com/TremDelayAddedFX
Same as above, but with a phaser, auto wah, reverb and EQ added.  Just to demo some of the possibilities.

The TremDelay files are large files.  Just a warning.  Never mind some of the distortion (crackle, lo Fi type) that you hear.  I was recording a little hot on the audio card when recording and there were a number of places where the signal was clipped at the input.  The distortion is not coming from the Trem/RingMod circuit.  I looked at a triangle wave on a scope fed through at 250 Hz and did not see any visual distortion at the output, so I know the circuit would not be causing that kind of distortion---that severity of distortion is visible in the audio tracks and on a scope.

Any suggestions for a brutally simple way to rectify the carrier ramp signal into a trangle, and a quite simple nonlinear tri to sine converter or links to such circuits would be appreciated.  Sines, Tri's and filtered square waves tend to generate much more clean and convincing bell tones.  I like the ramp carrier because it leaves some ratty edges that really sound analog synth-like, but for having a versatile and massively tweakable pedal would be nice to have the tri and sine in addition to the ramp.  Square, and even PWM square pulses will be very simple to pull out of the ramp with one comparator.

[Jaicen_solo]

I gotta say bravo on this one! I can't even pretend to understand what you're doing here, but it sounds brilliant.
That ramping modulation is so different from the usual sine and hypertriangle we're used to!
I had thought of using a ramping oscillator witha an AD633 based ring mod, but I think it would cause carrier bleedthrough (according to the spec sheet it wants to see a pure sine for total cancellation). I agree that the 'ratty' edges are  really cool, makes a nice lo-fi edge to the sound. Can you record some more of just the ring mod in the higher ranges??
The NOFX track sounds brilliant as well. Keep up the good work!

[markusw]

Wow, impressive work, and the sounds too.... 

Any suggestions for a brutally simple way to rectify the carrier ramp signal into a trangle, and a quite simple nonlinear tri to sine converter or links to such circuits would be appreciated. 

Don't know if this of help but maybe you can get some ideas from this one http://aronnelson.com/userfiles/RS%20v6%20schem.pdf. At least the wave shaping section does ramp to square, tri and sine in fm and pwm mode.  I hav'nt yet built it completely but the "LFO/VCO + ramp/square wave fm and pwm part" is tested on breadboard. The remaining sections are supposed to work if my Spice sims are correct. Hopefully, we'll know more in a few days when I etched and populated the boards.

Markus

[Transmogrifox]

I had thought of using a ramping oscillator witha an AD633 based ring mod, but I think it would cause carrier bleedthrough (according to the spec sheet it wants to see a pure sine for total cancellation). I

It's worth a try.  Have you tried the AD633 as a ringmod with a sine?

I will see how this afternoon turns out, I may have a chance to record some more in the higher frequency range.  The carrier frequency ranges up to 18 kHz, which at first I thought might be too high, but it does bring in some subtle aliasing type sounds.

Markusw:  Thanks for the link.  How well does it shape the ramp to a sine?  It looks like it's pretty much a clip and filter kind of thing.  The rectifier part looked like it might be a good interesting way to keep it simple.That looks like a pretty rad circuit in itself.  You'll have to post sound clips when you get it built.

[Jaicen_solo]

I havn't really done much in the way of design i'm afraid. I initially intended to use an MC1459 or something, as it's readily available in the UK. Only problem is that it wants to see +15v to function. I hear that it is possible to run an AD633 on +9v, so I thought i'd give it a go. That said, I guess a voltage doubler could be used.
Anyway, my aim with this ringmod was to create a versatile oscillator to create a more interesting, lofi sound. I also intend to add some sort of filtering for even crazier tones.

[Paul Perry (Frostwave)]

I initially intended to use an MC1459 or something, as it's readily available in the UK.

Lucky you didn't! because, I suspect the multiplier you are thinking of is the MC1495, and it has been out of production for a decade.

[Transmogrifox]

Can you record some more of just the ring mod in the higher ranges??

Here they are.  I'll keep adding as I get them uploaded.  I sat down and just tweaked with it for about 30 minutes constantly recording then listened back through it.  When I heard something I liked, I exported the section as a .wav file (later converted to mp3).   So here it is:

http://media.putfile.com/RingFun3
http://media.putfile.com/RingFun4
http://media.putfile.com/RingFun5
http://media.putfile.com/RingFunz14

[petemoore]

  Very "Alien', yet quite musical...very nice ! ! !
 

[Dave_B]

#4 sounds harpsichord'ish to my ears.  This thing is cool, Ryan.  Nice work!

[Transmogrifox]

Here are a few more.  It's almost obsessive now:

http://media.putfile.com/RingFun6
http://media.putfile.com/RingFunz10
http://media.putfile.com/lowbassringmod

I was just having too dang much fun playing with it.  It's amazing how much the use of good stable ramp generator cleaned up a ton of noise and carrier bleed-through.  The only problem is that headroom becomes a problem for powerful pickups if the power supply sags much below 8 Volts.  Maybe I should look into some rail to rail opamps.

Thanks all for the "kudos".  I'm hoping I can put a diy project of it together for the more ambitious types.  It certainly has a little more to it than a FF or MOSFET booster.