I built a EA Trem ROG version.  When I play into a clean amp the Effect is strong.  When I play into a distorted amp or dirt box the effect is lost until the signal starts to die down.  Is there anyway to tweak the Trem so the effect is strong with distortion without using a dirt box in front of it?  I am basically looking to get somewhat of a toggle switch on /off type of effect.

Quote from: dosmunI built a EA Trem ROG version.  When I play into a clean amp the Effect is strong.  When I play into a distorted amp or dirt box the effect is lost until the signal starts to die down.  Is there anyway to tweak the Trem so the effect is strong with distortion without using a dirt box in front of it?  I am basically looking to get somewhat of a toggle switch on /off type of effect.

easy....i'll give you a drawing in a moment...

andy

...heres a drawing for you...it uses a DPDT footswitch to toggle between 2 volume pots, so its convenient for live performance....if you didnt have the space in your enclosure for a 2nd pot, then you could use a fixed resistor or trimmer pot internally instead of pot #2...

also, if you use a 3PDT footswitch (instead of the DPDT), you could use the center lugs of the top and bottom rows to go to the neg side of an LED, so you could tell which volume pot you were on at any given time...

andy
dragonfly fx

BTW....you can also set up your "rate" and "depth" pots this way....you'd have 4 footswitches and 6 knobs !!!!  but you'd also have MANY different tremolo's at the stomp of a switch or two...

think about it....

you could have....

*vol 1, speed 1, depth 1
*vol 1, speed 2, depth 1
*vol 1, speed 1, depth 2
*vol 1, speed 2, depth 2
*vol 2, speed 1, depth 1
*vol 2, speed 2, depth 1
*vol 2, speed 1, depth 2
*vol 2, speed 2, depth 2

all at your feet at any given moment !!!!

<come to think of it, i'm gonna build one this week for myself !!!!>

Andy
Dragonfly FX

What do you use for a value of the 2nd pot?   Since ROG changed some resistor values.  Will that need to be adjusted as well?  What exactly is changing to a new pot going to do?

Quote from: dosmunWhat do you use for a value of the 2nd pot?   Since ROG changed some resistor values.  Will that need to be adjusted as well?  What exactly is changing to a new pot going to do?

you use the same value as the original pot...you just set one for your "louder" setting, and one for your "softer" setting...the switch merely toggles between them, so no need for any changes to the circuit.

andy

...or....maybe i'm "misreading you....are you NOT getting enough push, even with the volume pot "all the way up"

if thats the case, then further mods would be necessary.....

...though ive built a few from the ROG layout, and they had a TON of boost available....


andy

btw...for the npn transistor, try a MPSA18 or NTE47 instead of the one recommended by ROG (2n5088 ?) ...it'll modulate better through the full range of the depth/rate pots, and still wont distort

It is not the boost I am looking for.  I am assuming that the input signal is split and the out going signal is the mix of the straight signal and the affected signal.  I can run a distortion in front of the Trem and get a real intense effect.  I was just wondering if it is possible to get that same intensity with the distortion after the Trem because I usually use the amps distortion.

Quote from: dosmunIt is not the boost I am looking for.  I am assuming that the input signal is split and the out going signal is the mix of the straight signal and the affected signal.  I can run a distortion in front of the Trem and get a real intense effect.  I was just wondering if it is possible to get that same intensity with the distortion after the Trem because I usually use the amps distortion.

ah ha !!! i see.....

well.....

umm....

...dont have an answer for you on that one...i "doubt" you'll be able to get the intensity with the distortion "after" the tremolo, simply because the trem circuit isnt being pummeled into submission by the distortion..

but....hopefully someone will chime in and prove me wrong !


good luck,
andy

Someone who knows what they're talking about correct me if I'm wrong, but it seems to me that distortion is also compression.  Compression = loss of volume dynamics.  So, if you've got a wobbly signal going into a distortion, the compression will smooth it out.

I don't know how you're going to get around that.

Of course, it's also possible that I'm entirely wrong.  It's happened before.  

Yes...distortion after tremelo can blur it to non-existance.  Your best bet is to use a pedal for the grind & run the trem after it.  Or use a Fender which is equal to having trem last in the chain.

I have also found that the ea tremolo isnt very effective when distortion is applied after it. I came to the same conclusion as smashinator too.

I guess the problem is the 'depth' of tremolo that the ea circuit produces, ie not enough.  If Q1 on ROG's circuit was to almost completely reduce the output signal to zero (at the trough of the effect) then you should hear a tremolo effect even if distortion is applied after it. This is certainly the case with other trems i have tried.

I have been messing with the circuit a bit to try and squeeze some more depth out of it - so that it tremolos with distortion, and sounds choppier.

This has been my thinking:
I understand that the circuit around Q1 is basically a common emitter amplifier, and its gain is set approximately by Collector resistor/Emitter Reistance. In this case its 4k7/(180+(1k2 in parallel with the effective resistance of Q2)). I set the depth pot to pruduce max depth and measured the effective resistance of Q2. I found that it swung between roughly 3k and 8k. Can anyone verify this?? That would be a big help.

This struck me as being a bit odd, just because the 1k2 resistor its in parallel with will always 'dominate' the effective resistance of the 'emitter resitance'. My thinking was therefore to increase the 1k2 resistance to about 8k so that the resitance seen at the emittance has a larger variance with the swing of Q2. I think that this has produced more depth in my tremolo.  :roll:  Is anyone able to try this out to see that im not being stoopid?  Incidentally im using the original ea circuit (posted on RG site) with a BC108 as Q1, though that circuit isnt massively different to the one on ROG.

matt

Quote from: mveitchI have also found that the ea tremolo isnt very effective when distortion is applied after it. I came to the same conclusion as smashinator too.

I guess the problem is the 'depth' of tremolo that the ea circuit produces, ie not enough.  If Q1 on ROG's circuit was to almost completely reduce the output signal to zero (at the trough of the effect) then you should hear a tremolo effect even if distortion is applied after it. This is certainly the case with other trems i have tried.

making Q3 a higher hfe transistor, such as a MPSA18 or NTE47 will help with the depth issue....

andy

Paul Marossy's site has a link to *another* site that hosts a scan of the original 1968 Electronics Australia article.

The various diy incarnations have mutated, but the circuit analysis is worth the read.

I think I used a 1N4401 for Q3, and a 1M for the depth pot. Gets quite choppy - almost on/off. I changed about every other part, too, though...