Hi all!

Any recommendations for a ring mod with an adjustable frequency that works well with guitar?
I've found plenty of DIY ring mod-like circuits that make crazy clangy noises, I'm looking to build something that I'll use tuned to the key of the song I'm playing (Joy Landreth uses one like this, check this out: )

So far the main option is Craig Anderton's EPFM ring mod (project 9), with Mark Hammer's mods to control the carrier frequency a bit: https://www.diystompboxes.com/smfforum/index.php?topic=119112.0
I've got a 4011N NAND chip sitting around at home, and there are plenty of simple 4011 ring mod designs out there for synth, so the second option is to add a sine wave generator to the front of one of these. Nulling out the carrier signal might be difficult with these, tho.

I've found threads on the String Ringer (DIY Lovetone Ring Stinger), but it's huge and more complicated than I need, plus I've had trouble finding a PCB.
There's the Maestro Ring Mod, GGG has schematics and build docs but no PCBs for sale.
PCB Guitar Mania has a wild looking Flaming Lips ring mod which kind of appeals, but I'm not sure whether it's tunable or just for crazy sounds https://pcbguitarmania.com/product/death-by-flaming-ring-australia/
The Fairfield Randy's Revenge would be a great option, but I can't find DIY versions out there.

Any suggestions?

Cheers, Pat

Do it in the digital domain with an FV-1.

Logan 5 is OK, though not necessarily that quiet. Simple build though, low parts count.


The Flaming Lips version does have adjustable frequency, like the String Ringer, but like you stated, the SR is a big build. Both are available in PCB format from a couple of vendors.

Additionally, if on the fly frequency control appeals to you, the Royal Cosmo Wah is pretty cool. Combo wah and ring mod in one package. Unfortunately, the Snarling Dogs Mold Spore is still on our to do list. The dual pot arrangement presents a bit of a pain to work around.

Thanks Larry and digi2t

The FV-1 is a cool idea, I've never dabbled in digital for DIY, I'll look into that.
Ah, thanks for pointing that out digi2t, I hadn't read the blurb correctly.
An LM567 build is looking like a good option. If I leave out the transformers from the Flaming Lips one it's got the features I'm looking for (adjustable frequency and clean blend), and there's a good amount of info on the web about keeping the carrier signal as quiet as possible (filtering, diodes, etc).

Love all the stuff on your site! Some amazing things on there - the Royal Cosmo Wah looks bonkers!!

I wonder if Logan works with a regular LM567, or requires the low-power LMC version of the IC.    I have a bunch of LM567s right here.

I find one of the critical things to be mindful of, when using a ring mod, is the bandwidth of the input signal.  Keep in mind that RMs were first explored using PURE tones, like sine waves, for both carrier and modulator.  Once the harmonic complexity (and stability) of either or both of these increases, one starts to get results much less bell or rubber-band-like, and leaning more towards sheer noise, where you have sums and differences of MANY frequencies.  If noise is what you want, fine.  But if you're looking to use it to add some colour to things that can feel like they "want" to be at least somewhat melodic, then you'll want two things: 1) the ability to tune the modulator down below 150hz or so, and 2) rolling off the highs with the guitar's tone control, an external filter of some sort, or suitable filtering built into the RM itself.

For my money, one of the best, and most consistent, users of ring mod on guitar is Wayne Krantz.  We know he has used an EHX Frequency Analyser in past.  Which model, for how long, and what he uses now, is beyond my knowledge.

Quote from: GibsonGM on August 20, 2023, 07:33:13 AM
I wonder if Logan works with a regular LM567, or requires the low-power LMC version of the IC.    I have a bunch of LM567s right here.

I can't remember which I used, but the datasheet states that the C also offers double the oscillator frequency range.

It might remain to be seen if that's a good or bad thing, LOL. You know...ring mods....either really really cool or total garbage.  But everyone should have one for show and tell! 

If I were to design a ring modulator, I would start with an MC1496 analog multiplier (or the much rarer MC1495 that is designed for precision DC multiplication) because this allows pure multiplication without the generation of harmonics from square waves or switching devices.  Mark is right, once you get harmonics into the picture, any number of intermodulation effects can happen and these result in unpleasant noise.  Keeping the inputs within the linear range of the multiplier can be a problem but solving problems like that is why you are making the big bucks.

I do like making the big bucks!
Step 1: Ring mod
Step 2: ...?
Step 3: Profit! 

Quote from: Mark Hammer on August 20, 2023, 08:18:24 AM
I find one of the critical things to be mindful of, when using a ring mod, is the bandwidth of the input signal.  Keep in mind that RMs were first explored using PURE tones, like sine waves, for both carrier and modulator.  Once the harmonic complexity (and stability) of either or both of these increases, one starts to get results much less bell or rubber-band-like, and leaning more towards sheer noise, where you have sums and differences of MANY frequencies.  If noise is what you want, fine.  But if you're looking to use it to add some colour to things that can feel like they "want" to be at least somewhat melodic, then you'll want two things: 1) the ability to tune the modulator down below 150hz or so, and 2) rolling off the highs with the guitar's tone control, an external filter of some sort, or suitable filtering built into the RM itself.

For my money, one of the best, and most consistent, users of ring mod on guitar is Wayne Krantz.  We know he has used an EHX Frequency Analyser in past.  Which model, for how long, and what he uses now, is beyond my knowledge.

Thanks Mark, that's great - that'll explain why ring mods sound so different (to my ears more harmonious) in synth demos than guitar.
A filter on the input is a great suggestion, I was thinking of adding a compressor to the front end as well to even out the level going through it.
Great shout on the EHX Frequency Analyser, thanks! There's a tagboardfx stripboard layout for both the old and new versions, and I like that it's got such control over frequency and a clean blend.
I wonder whether the "Fine" settings/position of the pot are consistent over each octave to allow you to get close to the note you're tuning to by adding some markings and lining up the dots...

Quote from: GibsonGM on August 20, 2023, 07:33:13 AM
I wonder if Logan works with a regular LM567, or requires the low-power LMC version of the IC.    I have a bunch of LM567s right here.

That's right, LMC567 is one of the various changes for other circuits as well as the other options I listed, thanks.

Quote from: amptramp on August 20, 2023, 10:28:32 AM
If I were to design a ring modulator, I would start with an MC1496 analog multiplier (or the much rarer MC1495 that is designed for precision DC multiplication) because this allows pure multiplication without the generation of harmonics from square waves or switching devices.  Mark is right, once you get harmonics into the picture, any number of intermodulation effects can happen and these result in unpleasant noise.  Keeping the inputs within the linear range of the multiplier can be a problem but solving problems like that is why you are making the big bucks.

In another ring mod thread on the forum there's a suggestion about the Fairfield Randy's Revenge:

Quote from: nocentelli on September 26, 2013, 09:57:23 AM
There is a thread at the Pariah place that has Mr Fairfield himself dropping clues about what's inside, but no schematic or pictures even. I'm not sure pictures would be enough to trace it fully either, since most Fairfield pcbs are apparently multilayered and somwhat tricky to reverse. The pertinent facts dropped are that it's run on +/- 9v from an ICL7660, uses an AD633, and has 2 LM13700s to produce a phase shift oscillator. He says he started with what was in the datasheet, and worked from there....

I'd feel reasonably confident about putting together a design based on datasheets, so I could have a go at that using the MC1496 or AD633 for a fun challenge.
The EHX versions use each of those and tick the other boxes I'm looking for in a ring mod, so I might well start by building one of those and add on a LPF and compressor at the front end after the input buffer stage to do the filtering as Mark suggested and even out the signal

Mark, I found Wayne's EHX Frequency Analyser - it's the modern version.
In this part of the rig rundown with Premier Guitar you can just see the "4" of the "40V" marking on the top peeking out from behind the middle knob

Quote from: patricks on August 20, 2023, 11:22:38 PM
I'd feel reasonably confident about putting together a design based on datasheets, so I could have a go at that using the MC1496 or AD633 for a fun challenge.

You'll find plenty of ring mods for synth use designed around these two chips. Obviously a +/-15V or +/-12V power supply makes life somewhat easier, but otherwise it'll be close to what you need. The AD633 is expensive but extremely accurate, 1496 is less so and less so. LM13700 for even cheaper and cheerfuller.

For example, Roman Sowa's version has been around for years:

http://sowa.synth.net/modular/m_rm.gif

HTH

I'm finding that out the more research I do. The AD633 and ICL8038 are more expensive than the typical "jellybean" ICs in most stompboxes, but not hens teeth and not too expensive.

Thanks for the link to Roman Sowa's version - I love all the cool things on your site, too. I'll have to choose carefully which articles I read, or I'll want to DIY a synth next... 

Ring modulators can be combined to give some interesting effects.  If you are multiplying cosines of two frequencies, A and B, you get:

sin A * cos B = 0.5[sin(A + B) + sin(A - B)]

then you have:

cos A * sin B = 0.5[sin(A + B) - sin(A - B)]

Add these two equations together and you get 0.5 sin (A + B).  Subtract the second term from the first and you get 0.5 sin (A - B).  Some of you may recognize this as the governing equations for single sideband modulation.  It takes a 90 degree phase shift from an allpass filter like the ones used in phasors to generate sine from cosine but this raises an interesting possibility: you could use this to get a vibrato that does not require time delay elements but always goes above (upper sideband) or below (lower sideband) the incoming frequency.

If you stick with linear multipliers, you don't get anything but these frequencies, so there are no intermodulation products of harmonics.  You might need a lot of trimpots to get the signal centred in the linear range, but it would give interesting results.  Diode modulators give you the fundamental plus odd-order harmonics and switching multipliers can have their duty cycle adjusted to null out certain harmonics as is done in some FM multiplex decoders, but only linear multipliers give you the true sidebands without additional intermodulation products.

Quote from: patricks on August 21, 2023, 06:02:58 AM
I love all the cool things on your site, too. I'll have to choose carefully which articles I read, or I'll want to DIY a synth next... 

Yeah, there's a crazy chip from Alfa which would do this job, three times over!!

https://electricdruid.net/datasheets/AS3363.pdf

Quite what you'd *do* with three ring mods in one box is not clear to me, but it's pretty remarkable. (The obvious application for such a thing is in the mod matrix of a analog synth, allowing different modulation signals to be affect different things with either polarity and variable depth). Perhaps Amptramp's frequency shifter is an example?

Simpler dual VCAs like the AS3360 or AS3330 would also do the job.

Turns out I've been blathering on about the same stuff for a long time, now!
https://www.diystompboxes.com/smfforum/index.php?topic=59881.0

This fellow is demonstrating his build of the EPFM RM with an envelope follower governing the modulating frequency, such that when he digs in, the sum and difference get farther apart and more dissonant; an interesting idea.  But, thinking it over, and given that the EPFM design provides for mixing of the RM and clean sound in an op-amp mixing stage, another approach could use and envelope follower to dictate how much of the RM tone is mixed in with the clean sound.  Put an LDR in parallel with the fixed resistor bringing the RM into the mixing stage (and raise the actual value of that resistor from what the EPFM schematic shows), and an envelope follower could drive the LDR+resistor value down, when you dig in, and make the resulting tone more "boing-ey".

The EH 8000 guitar synth if I remember used a quad exclusive or gate 4030 for its ring modulator, and jolly good it was too!

Quote from: StephenGiles on August 21, 2023, 03:57:48 PM
The EH 8000 guitar synth if I remember used a quad exclusive or gate 4030 for its ring modulator, and jolly good it was too!

That's a fairly common trick on synths with square waves. The Korg MS-20 did the same thing, although I don't know if it was the first (That'd be an interesting question to research). XOR is equivalent to 4-quadrant multiplication for signals with only two states, and one XOR gate is a lot cheaper than a full analog multiplier, especially back then. It gets pretty dissonant pretty fast because of all the harmonics, but if it's followed by a filter (as would be typical on a synth) then that's not necessarily a problem.

A ring mod with both inputs the same remains one of the methods of getting an octave up, since the sum of two identical frequencies is a DC level plus an output of twice the input frequency.  Most people use fullwave rectifiers but this generates a lot of harmonics.  A linear multiplier would not necessarily have an output quite as rich in harmonics.

Quote from: amptramp on August 22, 2023, 06:59:58 AM
A ring mod with both inputs the same remains one of the methods of getting an octave up, since the sum of two identical frequencies is a DC level plus an output of twice the input frequency.  Most people use fullwave rectifiers but this generates a lot of harmonics.  A linear multiplier would not necessarily have an output quite as rich in harmonics.

Not a ring mod, per se, but Aphex used the strategy of producing "exciter" content by modulating the audio signal fed to an OTA with itself.