Stereo Tremolo Output 2 inversion

[bside2234]

I'm thinking about building a tremolo and I would like stereo outputs (or two outputs whether it's true stereo or not 

How would one go about "inverting" the second outputs signal so I could use two amps and get that alternating tremolo effect rather than both amps pulsing at the same time?
I've tried searching all over and I can't find anything so I think I must be searching for the wrong terms.

Would this require two different LFO's sync'd together or is it possible to invert the second output without cancelling anything?

[MaxPower]

I'm a bit of a newb so there may well be better ways to do this. Anyways, op amps have an inverting and a non-inverting input (maybe that's just differential op amps?), so you could route the signal through two op amps, one through the inverting input and one through the non-inverting input. As for what op amp to use, I don't know. The 741 (uA741, LM741, etc.) is cheap so you can experiment with it and not lose any sleep over frying a few. Once you figure it out you can try op amps with better specs if needed.

Actually, I don't know if there's a noticeable delay added to a signal going through an op amp circuit and if there is, it may be a good thing as regards phase cancellation. So you might try running one output direct and one output through an inverting op amp (or a transistor, or FET) set to unity gain and seeing how that works out.

[duck_arse]

bside, search this site for the cardinal tremolo. it is most of what you want, I think, but might need some mods where it splits high/low, and at the output mixing. it will give you some ideas maybe.

[R.G.]

There are two issues here. I'm not sure what you mean.

The audio signal may be inverted or not, and the LFO may be inverted or not. I -think- you mean having the same audio signal to two amps, but having one amp get a loud signal when the other amp is getting a quiet signal, and vice versa as the tremolo modulates.

If that is true, you need to have synchronized, out-of-phase LFOs. It is far easier to generate inverted LFO signals in the same circuit than to synchronize them, although having them "hunt" to try to follow one another might be an interesting thing, too.

To get the alternating left-right, you make the normal LFO signal, then invert it with an opamp or two as Maxpower said - except that explanation hides a huge amount of complexity. LFOs exist more as a concept than a single real entity. An LFO is nearly always highly specialized to feed just the right amount of DC level and AC LFO signal to the thing it drives. And the "depth" control on an LFO nearly always includes complications of whether it leaves the LFO signal sitting at its middle value and expands both up AND down with increasing level, or whether it's at the upper DC level and expands down, or at the lower DC level and expands up.

So research the Cardinal and its precursors, back to the Fender high/low "vibrato".

[armdnrdy]

Also look at the Ibanez ST-810 stereo panner for ideas.

The LFO has an extra inverting op amp which creates an opposite pulse to the gate of a JFET.

When utilized in mono, this effect sounds like a tremolo. In stereo it's an opposite ramp up/down, left/right panner.

[bside2234]

Thanks guys.
@RG: Yes, that's what I meant. Two signals going to two amps. One loud while the other isn't to get that pulsing back and forth sound. I'll have a look at the other tremolos.

So on the ST-810, using this schematic: http://analogguru.an.ohost.de/193/schematics/Ibanez_ST-810.gif, IC2a is feeding output 1 and IC2b is "inverting" (I don't know if this is the correct term) or making the "opposite"
signal for output 2. Correct? Is it just the op-amp part or does the Jfet sections have anything to do with it?

[armdnrdy]

So on the ST-810, using this schematic: http://analogguru.an.ohost.de/193/schematics/Ibanez_ST-810.gif, IC2a is feeding output 1 and IC2b is "inverting" (I don't know if this is the correct term) or making the "opposite"
signal for output 2. Correct? Is it just the op-amp part or does the Jfet sections have anything to do with it?

Yes. IC2a output signal is the opposite of IC2b.

The JFETs have everything to do with it!
The JFETs act like variable resistors and "pull" the audio signal to bias voltage in unison with the LFO.
In other words, the JFETs are what causes the signal of each channel to ramp up and down.

Tremolo does the same thing. The volume is manipulated up and down. The ST-810 could be made a "stereo" tremolo by tying both channels to work in unison but......I think it sounds much better having the tremolo panned.