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Normalling the carrier of passive ring mod
MUFF WIGGLER Forum Index -> Fractional Rack Modules  
Author Normalling the carrier of passive ring mod
Spivkurl
So, I've begun my fractional adventure after buying a partial system from a fellow wiggler. It has a bunch of great modules already, and I've added two in the last week or so.

One of those added was a passive ring modulator, built to the general specs of the CGS design, and using some nice old USSR built germanium diodes. I matched them to the best of my abilities, and it has turned out sounding quite good! It's nice as is, but I have enough space on the DIY panel to include a simple oscillator (not VC, just manual) to use as a normalled carrier.

I have done some preliminary searching on the site, but have not found the solution to normalling this carrier with a switching jack for the carrier input.

I have tried the various obvious connections, but the ring modulator also acts as if there is no carrier present until I insert an external one. I know that the oscillator is running, as it has been viewed on a scope, as well as the direct output being heard by tapping right off the board.

So, my question is - Is there some sort of special grounding consideration when this passive ring modulator is normalled since it does not regularly share the common PSU ground?

My main experience has been with DIY banana modules, and this 3.5mm jack thing is a very different experience. Thank you for any help!
Spivkurl
Okay, in response to myself...

It looks like what I need is a jack with two switches, and not just a switch for the tip signal. This makes perfect sense, and I don't know why I didn't think of it! Possibly I have one from salvage work.

For future reference, what is the preferred 3.5mm jack with a switch for both tip and sleeve (or ring)?
Adam-V
You want to normal the oscillator to one input on the ring mod right?

A mono jack with a switch on the tip is all you require for that.

You just need to connect the oscillator output to the switch contact. and the tip contact to the input of the ringmod. When a plug is inserted into the jack, the oscillator signal will be disconnected and plugged in signal will be connected to the ringmod.

If you want to have the oscillator output available at the same time, add another jack with the oscillator output connected to the tip contact as well as the RM switched contact.

Connect all the sleeve contacts together and to ground

Hope I haven't confused you. Let me know if a picture would help and I'll see what I can do.

Cheers,
Adam-V
Spivkurl
Adam-V, thank you for your response.

What you propose is exactly what I attempted originally, and without success. EDIT - Rereading your response, it is not quite what I was attempting... I am using it as the carrier, and not the "input," which are not fundamentally interchangeable. The input and output are interchangeable, but not the input and carrier.

Then I hit on this schematic, which made it all make sense...

https://delptronics.com/documents/RingModulatorSchematic.pdf

My carrier oscillator is based on the CD4046 (one of my favorite CMOS ICs), and not the 555 though.

It works perfectly now, with the jack that switches both tip and sleeve. The problem was that the carrier input requires both, one to each secondary of the transformers. Without switching the sleeve, the oscillator is left without a reference, and the circuit was incomplete. I originally tried it with the ground of the oscillator both connected or not connected the the sleeve of the jack, but neither way would the oscillator carry the ring mod.

I have to do an adjustment to the CV input, but the ext carrier input works great, and I can use the output of the oscillator simultaneously for other modulations (FM etc...)

I am eager to have the CV part working... I could see it sounding very funky with a sample and hold plugged into it modulating the carrier frequency. The range is pretty huge, from like 1 Hz to nearly out of audible range. The very low frequency creates some excellent VCA style gating.
Adam-V
No worries mate, at least you got it sorted out.
Spivkurl
Haha, just edited to clear up confusion. hyper

Thanks again!
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