Odd question about a trem style circuit

[ThunderShowers]

Hey, I've been Missing from here for almost six years, but I'm getting back into this sort of thing again. The Voltage Pump Tube booster I built from learning here still is the star of my rec-room show, But now is the time for a new and exciting project. Apologies in advance if this is the wrong place to ask.

While I am great at seeing a circuit and modifying it, and understanding how specific things work and brute-forcing that to do what I want, when it comes to knowing technical terms, I find myself at a disadvantage, and that shows when i try to research or design something off the top of my head. That's why I've crawled back here.

For a while now I've been messing with stereo Guitar. No, not bridge/Neck stereo, I've been doing Bass/Treble. Three strings per channel, you get to run all sorts of cool effect splits (Octave down the bass side and Auto-wah the Treble for example) I want a tremolo/Spinning speaker style effect, which would be easy enough, but I'm not wanting On/Off. I want To swap Right/Left.

Therein lies the issue. Most tremolos are an up down amplitude control, Here I'm trying to get To different signal paths to swap. I have no clue where to even start. Any and all help is appreciated, and thank you in advance.

[mth5044]

Welcome back!

Some questions - are you looking to pan the treble and bass frequencies across each other? Such as one second you have treble on the left, bass on the right, then the next you have bass on the left, and treble on the right? If so, you're talking 2 inputs, 4 outputs.

Or are looking to take one signal, say treble, and pan it between left and right?

[GGBB]

I can't help you much I don't think, but I'm fascinated by the idea. Obviously there are stereo tremolos which would let you do "ping-pong" with a mono input signal (e.g. http://www.freeinfosociety.com/electronics/schemview.php?id=1100). It's no stretch to use two of these to process a "stereo" signal and buffer-blend the outputs to mix them back together, but synchronizing the LFO rates and depths would be the challenge. In the Anderton schematic, that seems straightforward enough in principle at least - duplicate the two channels with two in phase and two out of phase - one of each for each channel of the input signal. Then buffer and blend channel A's in-phase output with channel B's out-of-phase output for one output channel, and vice-versa for the other output channel.

If you build something - please post sound samples!

[ThunderShowers]

Welcome back!

Some questions - are you looking to pan the treble and bass frequencies across each other? Such as one second you have treble on the left, bass on the right, then the next you have bass on the left, and treble on the right? If so, you're talking 2 inputs, 4 outputs.

Or are looking to take one signal, say treble, and pan it between left and right?

Two in, two out. You are correct about panning left to right, but this has to be contained to two amps. This is the prototype to a more ambitious project as well (Individual string per channel.)

I can't help you much I don't think, but I'm fascinated by the idea. Obviously there are stereo tremolos which would let you do "ping-pong" with a mono input signal (e.g. http://www.freeinfosociety.com/electronics/schemview.php?id=1100). It's no stretch to use two of these to process a "stereo" signal and buffer-blend the outputs to mix them back together, but synchronizing the LFO rates and depths would be the challenge. In the Anderton schematic, that seems straightforward enough in principle at least - duplicate the two channels with two in phase and two out of phase - one of each for each channel of the input signal. Then buffer and blend channel A's in-phase output with channel B's out-of-phase output for one output channel, and vice-versa for the other output channel.

If you build something - please post sound samples!

Aye, that sounds much like what I'm going for, and it's a good place to start. I might be a bit tired or I would have gone "Oh yeah, stereo tremolo is already a thing..."
Syncing does seem like that hard bit, as well as the blend, as that's quite a bit beyond where I've been. What I'm really looking for is, yes, that ping-pong Bass and treble swapping sides, but also the ability to get a slow spinning feel. I feel like there should be a way to use a single LFO source for that (Some way to split it and inverse the one wave maybe? I'm probably envisioning this wrong) but the technicality is beyond me. I'm a 555-Timer-LFO, Lowtech solution sort of guy, so this is a bit beyond me on the technical side at this point, But digging I will go - Any other pointers in directions for circuits to work into each other I will take.

[Rob Strand]

Therein lies the issue. Most tremolos are an up down amplitude control, Here I'm trying to get To different signal paths to swap. I have no clue where to even start. Any and all help is appreciated, and thank you in advance.

Sometimes it's how you think about it.   

Plan A:  Start with what you know

If you had two separate tremolo's it is easy to understand.   The trouble with that is the two channels would be out of sync.  So the problem to be solved is how to take make them sync, or more likely sync in opposite phase.

So you take two circuits but only have one LFO, so that guarantees they are synced.    Now imagine inverting the LFO  so now it goes up when the other is going down.  Now you feed one circuit with the raw LFO and the other circuit with the inverted LFO.  That is pretty much one possible way of doing it.

However, it's not quite there.    The control signal, say to a JFET, will swing between voltage Vlo and another voltage Vhi.  When you invert it it will go -Vlo to -Vhi.     So you don't want to invert it you want to flip it about the middle (Vlo + Vhi)/2.    You would do that by feeding the LFO into an inverting amplifier with the +input wired to a DC voltage (Vlo + Vhi)/2.

That's only one way to go about it.  It's probably not the cleanest way to do it but you have to start from something you know.    There some very subtle things that might be objectionable to the purists.   For example the LFO might not be a pure sine wave the top might be fatter than the bottom.  When you invert the sine wave like I have described the fat part gets moved to the bottom.  Another issue is when the battery goes flat.  Will the middle of the LFO stay in the right place?  Yet another issue is getting the idea to work when you have a depth control.

Plan B:  Find similar ideas and copy them.

Think about stereo effects with modulation.  You might come-up with chorus units.  However you can also get Leslie simulators.    Have a poke around at those type of circuits for ideas.


BTW: I'm pretty sure I've seen a stereo tremolo somewhere.

[Rob Strand]

I should have kept reading down the thread.

Bass and treble swapping sides, but also the ability to get a slow spinning feel. I feel like there should be a way to use a single LFO source for that (Some way to split it and inverse the one wave maybe? I'm probably envisioning this wrong) but the technicality is beyond m

A crossover circuit used for speakers is one place to start.   There's quite a few configurations possible not all giving the same result.

In concept you can use a stereo tremollo and a crossover.   
The trick is to mix the high from one channel with the low from the other using a simple summer.

Input signal  ------>   Stereo Tremollo  ----> L   --->    HPF1-------------------\
                                                                     --->   LPF1---------+--------------- Lout
                                                                                                |             |
                                                       ----> R   --->    HPF2---------/            |
                                                                     --->   LPF2--------------------+---- Rout

+  = summer

Other options could move the crossover point around.

[ThunderShowers]

I should have kept reading down the thread.

Bass and treble swapping sides, but also the ability to get a slow spinning feel. I feel like there should be a way to use a single LFO source for that (Some way to split it and inverse the one wave maybe? I'm probably envisioning this wrong) but the technicality is beyond m

A crossover circuit used for speakers is one place to start.   There's quite a few configurations possible not all giving the same result.

In concept you can use a stereo tremollo and a crossover.   
The trick is to mix the high from one channel with the low from the other using a simple summer.

Input signal  ------>   Stereo Tremollo  ----> L   --->    HPF1-------------------\
                                                                     --->   LPF1---------+--------------- Lout
                                                                                                |             |
                                                       ----> R   --->    HPF2---------/            |
                                                                     --->   LPF2--------------------+---- Rout

+  = summer

Other options could move the crossover point around.

You're not quite envisioning the Left/Right split here, though what you're onto is also a really cool idea. Regardless, In essence:

Left Channel is (Bass) EAD Strings
Right Channel is (Treble) GBe Strings
I want to have them switch sides.

[Rob Strand]

You're not quite envisioning the Left/Right split here, though what you're onto is also a really cool idea. Regardless, In essence:

Left Channel is (Bass) EAD Strings
Right Channel is (Treble) GBe Strings
I want to have them switch sides.

Sorry,  now I'm on channel.  Thanks for spelling it out.
It's actually Stereo in and Stereo out.


Lin   ------>   Stereo Tremollo1  ---->  LA  ------+------------- Lout
                      |                                              |
                      | LFO link         ---->  LB  --------------\
                      v                                              |      |
Rin   ------>   Stereo Tremollo2  ---->  RA -------------+------ Rout
                                                                     |
                                               ----> RB -------/

That's the concept.  The ckt could probably be squashed down.
EDIT: Forgot to add each tremolo has it's two inputs tied together.