Ultimate Ring Modulator

[Rodgre]

Okay, what gets your vote for the ultimate in buildable ring modulator circuits?

what are your thoughts on the EH Frequency Analyzer? The Ring Frobnicator? the Paia balanced modulator module? The Craig Anderton EPFM circuit?

Others?

One of these days, I would like to make a seriously fine sounding clang machine. I love the Moogerfooger, but I can't afford it at the moment, or at any moment in the near future.

I love how the Moog will turn into a fantastic tremolo if you set it right. Besides the Frobnicator, can others do this as well?

Should I just build the frobnicator and be done with it?

Roger

[gtrmac]

I wish someone would come up with a more modern circuit for this effect. A design using the AD-633 chip would be nice. there is a schmatic of the modulation circuit but the oscillator is not included.

[brett]

Should I just build the frobnicator and be done with it?

Best not to expect too much from the Ring Frobnicator.  It lets thru a lot of modulator signal, so you'll either need a noise gate or be able to play continuously (only kidding).

A couple of weeks ago I put up a schematic and PCB for something I called the "Modulatron".  It's a balanced modulator that has the lowest bleed-thru of any modulator I've heard so far (ie better than the CA3080 and LM13600 based designs).  And it could probably be made much quieter with some re-design by the experts that frequent the forum.  At present it's "almost useable" in terms of modulation noise.  In standard form it modulates down to about 30Hz, which sounds like a very fast tremolo.  That can be easily lowered to 3Hz by changing the 0.01uF cap on the 555 to a 0.1uF cap.

cheers

[Zero the hero]

As suggested by brett, I do not reccomend Ring Frobnicator: I had much problems with this unit! Carrier signal was so audible and guitar signal was almost absent from modulation. It drove me crazy and in the end I dismantelled that circuit.
So I've built the Maestro. There's a big problem with this one: as stated previosly in this forum, MC1495 is almost impossible to find...
Ring modulators based on AD633 chip use the same tech of the maestro (four quadrants-multipler chips) and the results should be the same.
Intersil produces an intersting four quadrant multiplier, if I find the datasheet I'll post it here...

[Zero the hero]

That's here: http://www.intersil.com/data/fn/fn2477.pdf

[Mark Hammer]

Here is a shopping list of the things you want from a ring modulator.  Not all will be obtainable from every unit, commercial or DIY.

1) Ability to eliminate the carrier signal.  This is the steady signal you use to produce sum and differences.  In many instances you get leakage of that signal.  It is not that annoying when covered up by the guitar signal, but if you can still hear it during the silent parts it gets very annoying very quickly.  Some units provide a "null" adjustment to reduce and even cancel the carrier from the output signal, and others may simply be designed to remove it.  Since small amounts of carrier leakage are not easily noticed during musical passages, careful use of a noise gate can solve most of whatever good design hasn't. This isn't so much a performance control issue as one of usability.

2) Blending of affected and unaffected sound.  RMs "depitch" the sound by varying amounts, and since most guitar players will want a RM to enable them to play something that sounds *sort of* pitched now and then, injecting some dry signal in with the RM signal helps to maintain a sense of notes going higher or lower.

3) Wide range of modulating/carrier frequencies.  The lower the modulating frequency the more the resulting effect sound will seem pitched.  So, a modulation frequency of 40hz will produce outputs of 260 and 340hz when used with a 300hz input frequency, and outputs of 960 and 1040 when used with a 1khz tone.  Having a wide LFO range allows you to adjust the modulating frequency to suit the purpose you intend (i.e., mostly pitched or wacko) AND the note range you intend to pursue it in (higher vs lower notes).

4) If you can't have a decent on-board LFO, then opportunity to use an offboard/external LFO or VCO is desirable so that you can nail the sort of modulation you want.  Presumably that LFO/VCO will let you have control over the modulating waveform as well as frequency range.

5) Modulation amount.  Not every RM lets you adjust how much the carrier will modulate (i.e., LFO amplitude) the input signal.  If you can dynamically vary the modulation intensity (and this would likely be easier if the unit employed an outboard LFO) that's even better (morph from normal to wacko over the course of a note).

6) Frequency doubling.  Feed the same frequency into the X and Y inputs and you double the frequency (sum of a frequency and itself is 2xfreq, difference of a frequency and itself is zero).  Not all permit you to use the input signal itself as a source of modulation.

7) Input filtering.  The closer to a pure tone your input signal is the less cluttered the RM output will be (less of all the sums and differences of the carrier and harmonics).  Having some capacity to vary the lowpass filtering of the input signal is just as helpful as being able to vary the waveform of the modulating signal....maybe moreso.

I'll leave it at that, and suspect that others will add to this shopping list of features.  There are, I suppose all the usual things you want in a pedal, like low noise, no undesirable distortion, low power consumption, decent switching, etc.

[ExpAnonColin]

There's also an analog devices chip that's a quad quad quad multiplier (AKA quad 4 quadrant multiplier).  4 in one chip.  I have as a sample, I've never used it.

Here's my favorite design to start with:



There are a couple more in the archives.

-Colin

[Paul Perry (Frostwave)]

Different people want (and expect) different things from a ring modulator. For a classic ring mod, without bleedthru, I'd vote for that ckt from Tomboy with the AD633. And those trimmers.. make them 10 or 20 turn!

[Zero the hero]

Maybe a sine wave generator will sound smoother... I'll try this mod when I'll build it

[Paul Perry (Frostwave)]

Zero, it would be pretty simple to put an "overdriven OTA" tri to sine converter in this. By that time, you would be well on the way to matching my Blue Ringer.. and a good mod to have is external input as alternate to the local oscillator, and voltage control of the local oscillator