Is a stereo EA Tremolo possible?

[sevenisthenumber]

Just wondering.
Someone kill my dreams or encourage me in this random thought...

[Mugshot]

this thread is relevant to my interests. 

[jkokura]

How stereo? Like the same output twice? Or like a back and forth effect like the Line 6 Modulation 4 unit gave me?

If it's the former, it could be as simple as just wiring a second output jack. If the other, than it will be a little bit more work and I'm not the one to talk to.

[phuzle]

you could do a buffer at the input that splits the signal into two identical EA trem circuits, each with separate but identical controls, which go to two outputs.  then you can dial in different speeds for each output.  maybe even add a blend circuit in case you don't want stereo.... sounds pretty cool to me, and with the simplicity of the EA trem, it would be pretty easy.

[mac]

i'd split the signal into 2 ea trems. and i'd use the same rate for both, but in anti-phase, ie, when one is +1 the other is -1.
i'd use one LFO to keep sync but... anti-phase??? LDRs???
if amps are a few meters away the fx would be cool.

mac

[R.G.]

Just wondering.
Someone kill my dreams or encourage me in this random thought...

Is it possible? Sure. The simplest thing is to make two.

That may in fact be the optimal way to make one. If you use a dual ganged speed pot, you get close-but-not-perfect frequency tracking so the LFOs wander around relative to one another, making for a much more interesting sound than simple antiphase LFOs.

But you can make one LFO and invert the LFO signal for the other modulation section too.

This sounds GREAT if you have two amps, one on each side of you. But as Mark Hammer notes, it may not project to the audience very well.  Even more interesting might be to have a Fender/ersatz Fender "vibrato" on one side and some other modulated effect on the other; very interesting auditory effects. Again, getting this same thing to happen at the head of each audience member is tricky.

[Mark Hammer]

Here's an idea.

The implementations I have seen of the EAN Tremolo which use a rate indicator LED (like the one shown here: http://www.runoffgroove.com/EAtremolo.png ) actually end up illuminating the LED in opposite manner.  That is, even though it is perfectly synced to rate, the LED gets brighter as the output lowers, and dimmer as the output gets louder.  So, if you aren't that fussy about seeing the flashing rate LED, you can use that LED to shine on a photocell and implement that photocell in a circuit that varies volume, gain, or both.  The fact that the photocell may have some lag built into it may mean that you end up with something that is in between precisely syncronized panning and what people strive for when they use a quadrature oscillator for panning.  So, it wouldn't be 180 degrees different, but rather 185 degrees, which will likely make it more musical-sounding and palatable (hard panning does get dreary pretty quickly).

And since we're off on a counter-intuitive tangent here, consider that the LED could also be used to modulated something else.  Like, say, the rate on a phaser.  So as the tremolo output level drops, and the LED gets brighter, it shines on a photocell placed in parallel with the rate control of a Phase 90 or a Ropez, and increases the phasing rate/speed.  Then as the volume picks up again, the LED gets dark, the photocell resistance goes up, and the phaser settles down again.

That's merely one example of how the rate LED could be used in conjunction with a photocell and other "yoked" effects. 

There, that's enough lateral thinking for today.

[jkokura]

This sounds GREAT if you have two amps, one on each side of you. But as Mark Hammer notes, it may not project to the audience very well.  Even more interesting might be to have a Fender/ersatz Fender "vibrato" on one side and some other modulated effect on the other; very interesting auditory effects. Again, getting this same thing to happen at the head of each audience member is tricky.

I've done something similar RG. Playing live I used a stereo Trem and a panning effect between two similar Fender amps. The house guys had my amps panned L and R. They said that the effect of my slow pan back and forth in the house was phenomenal. But you have to be in a club or sanctuary (wherever you play) big enough for you to have your amps miked to have the effect really working for you.

The stereo Trem ideas above are more complicated than a simple dual output but the sound way more fun. However, how would those dual board with opposite LFO's work if, say for example, our OA here wanted  to use his trem in Mono one time? Would this effect only be useful in Stereo or could it be used anytime?

[Mugshot]

how about a mono EA Trem with a mono output but is chained to a mechanical panner (to two amps) with the panning synced to the rate of the effect?

[sevenisthenumber]

how about a mono EA Trem with a mono output but is chained to a mechanical panner (to two amps) with the panning synced to the rate of the effect?

that could be cool!

[PRR]

[Mugshot]

care to share how this'll work? 

[PRR]

> care to share

The pink part is an inverter. The rest is obvious: duplicated variable-gain stages.

There are MUCH more elegant ways to do stereo-trem, but this is what the thread-topic wanted to use.

[Mugshot]

what about the input? isnt it necessary to buffer the input before it hits the separate mosfet stages?

[mac]

The pink part is an inverter.

unity gain?

mac

[Mugshot]

good news peeps. i built PRR's hack on the EA trem and it sure does work! not perfed but soldered on a PCB. now for the more daunting task: switching. im thinking of doing a relay switch for this little throbber since i need at least 5 poles to switch this thing: two for the input, two for the output, one to break the LED connection. sigh, im a complete noob with relays. we only have 12v relays here, and im thinking of using the same 9v source to power the relay switch.

[earthtonesaudio]

Your bypass options open up considerably if you don't use True Bypass. 

You could ground each JFET gate with a DPDT for instance; or open-circuit the LEDs if you don't want the flashy lights when the effect is off.

[Mugshot]

Your bypass options open up considerably if you don't use True Bypass. 

You could ground each JFET gate with a DPDT for instance; or open-circuit the LEDs if you don't want the flashy lights when the effect is off.

actually im inclined to use a 3pdt or a 4pdt even (if available) and just use the poles to cut the connection to the 22uF cap and the other pole to break the blinking LED connection to the oscillation section. and yeah, the input and outputs are always connected to the first mosfet stage. so basically it would be just switching the oscillation in and out. since this is stereo it will be sitting last in the chain going into the amp, but not in the loop.

but if a 5pdt relay will give me tbp, why not?  now i have to exert effort to read RG's relay basics.

[earthtonesaudio]

Another way to get something other than 180 degrees of separation would be to make your tap for the second driver (i.e. the inverter in PRR's schem) at one of the other R-C junctions.  Each RC stage presents something like 60 degrees of shift, so you have 60 and 120 readily available as well, not just 180.

Heh... you could have a three-phase triphonic trem.   

The gain for this alternative driver would need to be higher, but that's easy.

[earthtonesaudio]

Another way to get the opposite-LFO output would be to take the signal from the mosfet source.  It will be less-than unity so you might want to tack on a high input impedance booster.