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Ring mod vs VCA
MUFF WIGGLER Forum Index -> Modular Synth General Discussion Goto page 1, 2  Next [all]
Author Ring mod vs VCA
Epignosis567
How is a ring modulator different than through zero AM?
In what ways?
Yes Powder
I don't think I've ever heard of it being called "through zero AM."
If you want to insist on it though, I'd say that maybe the input for "through-zero AM" would be DC-coupled while a ring-mod would be AC-coupled, but I can definitely think of so-called "ring-mods" that are DC-coupled so don't take me too seriously here because I sure as fuck aren't.

Also, this would really belong in "Modular Synth General Discussion" instead of "Eurorack Forums".
Epignosis567
1. Yes I was using the term “through zero AM” facetiously.
2. Yes I agree it would be better suited to that forum perhaps one of the mods could move it.
Epignosis567
I also do realize that they are different, I can hear and see on an oscillscope that they’re different, but when I’m asking is in what ways and how.
Nutritional Zero
Lasagna
Yes Powder
Epignosis567 wrote:
I also do realize that they are different, I can hear and see on an oscillscope that they’re different, but when I’m asking is in what ways and how.

Uhh... by my definition you could send a sub-audio range signal into a "through-zero AM" unit and use it as a voltage-controlled attenuverter?
I don't know if you were expecting it to be much interesting than that, because it really isn't seriously, i just don't get it
Ceres
It’s mathematically different. In AM the carrier frequency is present at the output and the sidebands are half the amplitude of that of the carrier.

As for the topic title. I enjoy using ring mods for VCA pursposes. Particularly colorful ring mods.
Graham Hinton
Epignosis567 wrote:
How is a ring modulator different than through zero AM?
In what ways?


If you want to use terms like that you could say that ring (balanced) modulation is through zero AM.

Ceres wrote:
In AM the carrier frequency is present at the output and the sidebands are half the amplitude of that of the carrier.


No, that is only the one specific case of 100% modulation. As modulation is increased the level of the carrier decreases and the sidebands increase. If modulation is >100% you get sections of zero level which produces even more sidebands. Balanced modulation has no carrier present.

A true diode ring modulator is really a switch and is like using a squarewave modulator with a multiplier. Again, more sidebands.
Shledge
I always thought they are interchangeable? Hence bipolar VCAs often being seen as ring mods.
dthorn
A ring modulator is just one specific type of circuit that performs through zero AM. All ring modulators are bipolar VCAs, but not all bipolar VCAs are ring modulators.
Shledge
What is an example of a bipolar VCA not being a ring modulator?
mbartkow
Shledge wrote:
What is an example of a bipolar VCA not being a ring modulator?


Every one that is not based on a ring of diodes. Eg. MI Blinds. Also, plenty of modules that bear the "Ring modulator" name, but inside are four-quadrant multipliers.
Shledge
I don't get the distinction since they both... pretty much do the same job - invert the phase of a signal when it goes through zero. It will generate the sum and differences like any other RM. The term may be from the arrangement of diodes, but it is now used for 4-quadrant multiplication in general. It just seems a bit pedantic and splitting hairs, similar to arguments people have had over "bitcrushers".
mbartkow
Shledge wrote:
I don't get the distinction since they both... pretty much do the same job - invert the phase of a signal when it goes through zero. It will generate the sum and differences like any other RM. The term may be from the arrangement of diodes, but it is now used for 4-quadrant multiplication in general. It just seems a bit pedantic and splitting hairs, similar to arguments people have had over "bitcrushers".


No, there is plenty of inaccuracies here. Inverting the phase of a signal when it goes through zero is the absolute value operation, also known as full-wave rectification, or hard wavefolding. It has nothing to do with any modulation, because it is an operation on a single signal.

Ring modulator is NOT a 4-quadrant multiplier. It is a switching modulator that just flips the polarity of the signal according to the sign of the carrier wave. It does NOT multiply in a linear way like the true 4q multipliers do. This is not hair splitting, a RM is a very crude modulation that even with sinusoidal input produces a lot of higher harmonics (unlike multipliers).

Also, multiplication DOES NOT equal sum and difference. It is a common BS often repeated by people who seem to ignore elementary maths*.



*) Actually, the "sum and difference" part refers to frequencies (and only in a very particular situation), not signals. It is completely not true if your signals are not pure sinusoids. A product of two signals in general has nothing to do with sums and differencies. Not to mention it never happens with a RM (for any signal), because it is NOT a multiplication.
Shledge
I meant that inverting phase = flipping polarity. Terminology wasn't on my side when I typed that.

A diode-based ring modulator is a crude 4 quadrant multiplier. The term "ring modulator" came from the the diode arrangement. The fact is that the term stuck for 4 quadrant multiplication in general. Even XOR functions get called "ring modulators". But lets get super pedantic and say they're all heterodynes, but that isn't fun...

Funny you mention rectifiers, considering diode ring mods look somewhat similar to bridge rectifiers...

Quote:
Actually, the "sum and difference" part refers to frequencies (and only in a very particular situation), not signals.


Yes, the frequencies. You're basically agreeing with me here despite claiming I'm repeating bullshit. Again, the only difference is that diode ring mods are crudely doing it.

Where are the inaccuracies? It hasn't changed my view on how this is really just being pedantic and splitting hairs. This is just like the types of people who try to argue over what bitcrushers are/are not.
mbartkow
Shledge wrote:
Even XOR functions get called "ring modulators".

Which is wrong. Synth manufacturers have long tradition of using misleading and plainly wrong terminology for marketing reasons.

Shledge wrote:
A diode-based ring modulator is a crude 4 quadrant multiplier.

Well, it is as much crude as calling an on/off switch a crude VCA. Is this splitting hairs here? If you cannot see/hear a difference between soft multiplier action and harsh full-volume switching polarity, and call it hair-splitting, then ok.

Shledge wrote:
Yes, the frequencies. You're basically agreeing with me here despite claiming I'm repeating bullshit.

You didn't say anything about frequencies, you said multiplication is adding and subtraction, which is nonsense.
Shledge
mbartkow wrote:

Which is wrong. Synth manufacturers have long tradition of using misleading and plainly wrong terminology for marketing reasons.


It sticks though, that is the point. Insisting what is/isn't ring modulation, especially when "ring modulation" itself as a term came from shaky ground out of the sheer coincidence of how the circuitry looks, is just pointless pedantry. It also stinks a little of gatekeeping too.

Quote:
Well, it is as much crude as calling an on/off switch a crude VCA. Is this splitting hairs here? If you cannot see/hear a difference between soft multiplier action and harsh full-volume switching polarity, and call it hair-splitting, then ok.


Never said that they should sound the same. In fact I'm quite aware that they don't - that's why bipolar VCAs are deemed to do "pure ring modulation". They're still both considered ring modulation by many since the differences needed to well... differentiate them is where the hair-splitting comes from. Both are 4 quadrant multipliers, just in crude/proper forms. You'd have a better point if you were comparing XOR ring mod instead. You'd have an excellent point if it were comparing ring modulation to frequency shifting.

Quote:

You didn't say anything about frequencies, you said multiplication is adding and subtraction, which is nonsense.


I didn't say "multiplication is adding and subtraction". Obviously I was talking about the sum and differences of the frequencies that ring mods typically produce.
ranix
the name "ring modulator" refers specifically to the diode ring. If there's no diode ring it's not a ring modulator

that would be like having a spring reverb with no spring
Shledge
Yes but again, the term stuck to apply to 4 quadrant multiplication/balanced modulation as a whole, purely because it itself is an imperfect, crude implementation of it. It's the same way FM is used for synths like the DX7, even though technically does phase modulation.

Even modules like Warps makes this distinction of implementation by offering diode RM, "pure" RM and XOR RM.
ranix
it didn't really, synth manufacturers just deployed 4 quadrant multipliers instead of ring modulators and labeled them ring modulators anyway because they sounded similar and accomplished roughly the same end purpose (ish) if you turned the knob on the front panel
Shledge
They sounded similar because... they are similar*. That's the entire point!

*except for XOR RM, which isn't really 4 quadrant multiplication.
ranix
yes, that is the entire point, they are smiliar and they are not the same
Shledge
The similarity is close enough to put them under one name. As you said, they did sound similar - and when you consider they're both just 4 quadrant multipliers anyway, then it's not hard to just call it "ring modulation". Having different names for practically the same effect is just a bit silly IMO.
Shledge
It's like distortion, or reverb - there may be many different ways to do them, and will all sound different, but they're still considered to be of the same effect.
ranix
yeah but spring reverb is spring reverb

Rex Coil had a thread awhile back on the 5u or diy forum (I forget) about his adventures with the CGS ring modulator and using different diodes to get radically different sounds from it. He had a whole thread about using LEDs as the diodes...

a ring modulator is a ring modulator and some other kind of modulator without a diode ring is not the same thing
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