Ken Stone active real ring modulator schematic

I have 2 questions about a schem
“Active Real Ring Modulator” of Ken Stone.

Again a question about the impedance of the 2 inputs signals

There are one input for Modular signal and one for Mic / guitar signal

plz , the red cross = modular in and thee green cross for mic / guitar ?

And the second question, i don’t understand the AC or DC inputs part for Carrier signal, if someone can simply explain what does it mean please.

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Does this help?

Also curious how this sounds different than the passive ring mods I see around.


yes thx i have read it, this schem come from this site but the informations are not really clear for me

for the sound it’s the same thing, just with opamp for synth level, because the passive one are very quiet/low

Well, the red x input is labeled “Mic/guitar”, and it has a gain stage with gain 11 (it says 10x in the description but it’s 11x right? 1+10k/1k?) so I’d say that’s right. Synth level is higher so that input bypasses that gain stage.

The AC input has a decoupling capacitor to remove DC offset from the input signal, the DC input doesn’t. There’s also a third input with an “unbalance” pot to add DC offset “thus changing its characteristics. The unbalance function is not unlike a wet/dry mixer.”


thanks a lot for your answer

Spinal Tap references in electronic design? I suppose it was inevitable.


I’m curious about the mix of NE5532 and TL07x op amps here. As I understand the NE5532 has lower impedance but lower noise, but it’s not at all clear to me how that influences the choice of which to use where in this circuit.

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Merely repeating myself

I’ve seen designs where 5532 amps are used for audio input and output stages, whereas tl07x are used for generic signal conditioning.

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it’s not really clear in the schem : “IN modular” / “Hi In” it’s for MIC/Guitar input infact

But here the 5532 is used for the carrier input and for the second stage of the signal input, TL07x for the first stage and for both stages of the output. Strikes me as haphazard but I don’t know much about this stuff.

I guess another way to put it is the 5532 is used for the synth level inputs and the TL07x for the mic/inst input and the outputs. From that point of view it’s less arbitrary.

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Seems “HI IN” is short for high impedance, not high level (it’s described as “high input impedance 10x” in the circuit description).

(also, TIL that TI just released a new TL07xH series with better specs, their datasheet was updated this month)


yes thx i better understand :slight_smile:

but it wasn’t clear “High Gain input” here

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Yes, the “mic/guitar” “hi input” is high gain (11x) because the signal is low level compared to synth.

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i not really understand the fonction of AC/DC input Carrier

the both are for synth signal in ?

all signal in modular is DC no ?

what the difference to use AC or DC input Carrier in a “real modular application”

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I think the confusion here is that the term “AC” is usually associated with “wall current”, the 110 or 230V you have in every house.
But in this context it means the literal Alternating Current. Which is when the signal goes negative during its swing.

Maybe this picture makes it clear

If you connect a biased signal ( which is always positive) to the AC coupled input, it will be “moved down” so it will swing around 0V.
What it means for the sound I have no idea :wink:


Ah thx a lot @sebastian , everything become more clear now :slight_smile:

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Me neither, but if you build it and mess with the “unbalance” input pot, you’ll find out.

(You could even replace the ground with -12V to make it work both directions.)

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I get the impression by reading up on wikipedia about the workings of a ring modulator that the ‘unbalance’ input will influence 2 of the diodes in the ‘ring’ by giving them a small constant current which probably makes the center point of the modulation move off center and create an unbalanced output signal. I’m not sure about this though, nor about how that will affect the sound.

This is what ring modulation does to a sine and a square wave:

See also:

@Dud Have you been able to find/buy the transformers as described in the schematic or are you improvising with some transformers you already have?


The modulator is made with 2 transformers 42TM018 and 1N60 germanium diodes.
To sum up, it was an old passive modulator project that I had done in a box, then wanted to turn it into a module, but it had a very low signal, I tried to add an opamp on the output, but I ended up not putting this module in my 3rd case.

I hope i’m going to end up putting it in my next one when I do it with this full active schematic.

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