Ross compressor: is the switch pop unavoidable?

[kvandekrol]

I've built three Ross compressors so far, in three different configurations, and all of them have the same true-bypass switch pop. Is this inherent to the design of the circuit, since it's going to amplify even the smallest signal when nothing else is coming through, or am I just doing something horribly wrong? Does anyone have a true bypass Ross compressor that does NOT pop when switching?

Here are the three variations I built:

1) Straight up Ross compressor from Tonepad (3PDT stomp switch)

2) Ross w/ mods: Mark Hammer's "release" switch, as well as a mod to switch the capacitor immediately after the IC for a different treble response (3PDT stomp switch).

3) Same as above, but with an AMZ relay bypass board.

The AMZ bypass was the quietest, but it was never completely silent (though the pop became less noticeable when the Sustain control was turned down).

I also experimented with a 1M pulldown vs. a 2M2 pulldown resistor on the input, and did not notice a difference with either the 3PDT or the relay.

If it's something I have to live with, that's cool - I just want to make sure there's nothing I'm (consistently) doing wrong, and was also wondering if there were any success stories out there...

[Steve Mavronis]

I've built several overdrives (250) and compressors (dyna comp) and never had a pop problem using this 3PDT wiring scheme:

http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b/

No pull down resistors and simple symmetrical pattern. The key is an extra wire on the switch grounding the PCB input when switched to bypass mode.

[kvandekrol]

The wiring method I use is slightly different in appearance but has the same result of grounding the PCB input. For the heck of it, I rewired one of mine to the gaussmarkov configuration on your link just now, but no change

I should also mention that I'm using different 3PDT brands as well... one is Cliff, and one is an unbranded Taiwanese w/ clear red epoxy.

[Steve Mavronis]

Hey just wondering; how are your input and output jacks grounded to your enclosure? Do you have good bare metal contact or is there any paint on the inside where they touch. I use inner tooth washers between the jacks and the inner box bare metal wall. Also that Gaussmarkov configuration grounds the switch to the output jack, which is ground with the input jack through the enclosure body. I use Switchcraft metal open frame jacks and a Cliff 3PDT by the way but don't think that matters? Maybe it's something different in the way your Ross Comp is modified from a straight Dyna Comp affecting the discharge pop. I hope someone offers a solution that works for you.

[kvandekrol]

Very solid ground connection for the input and output jacks. My ground connection is on the input, but the whole circuit is star-grounded at that point.

[Atodovax]

I also have the same problem. Star grounded, everything fine but huge POP when engagged. I even tried 47k  pulldown resistors on input and output with no luck. Anyone there knows how to work around this problem?

[Mark Hammer]

Any possibility it's pedal ventriloquism?  I.E., what is the supposedly offending pedal plugged into?

[amz-fx]

It may be that the trimpot needs adjusting. Try tweaking it a little bit to each side of the center to see if that helps.

regards, Jack

[Atodovax]

It may be that the trimpot needs adjusting. Try tweaking it a little bit to each side of the center to see if that helps.

regards, Jack

I have it settled exactly at the middle point (950 ohm on each leg) But i will try moving it a little bit and report back

[Atodovax]

Ok turning the trimpot did lower the POP but only at its extremities which made the compressor sound horrible... I finally lowered the the volume pot to 5k and this lowered the POP a little bit and also removed lots of treble which i dont like but i cannot think of another solution. I tried no LED, different 3pdt swtiches , star ground, mounted pots, short wires for input output, super neat build. I wonder if anyone with an original unit could clarify if this POP is something to be expected even with the orignal pedals

[WormBoy]

I built a Ross from the Tonepad layout (etched the board myself). Regular 3PDT true bypass, and almost completely silent when switched. Certainly no worse than any of my other pedals. Built another one for a friend on a PCB from Aion, and that's close to totally silent as well. So I don't think your problem is inherent to the circuit.

[Atodovax]

I built a Ross from the Tonepad layout (etched the board myself). Regular 3PDT true bypass, and almost completely silent when switched. Certainly no worse than any of my other pedals. Built another one for a friend on a PCB from Aion, and that's close to totally silent as well. So I don't think your problem is inherent to the circuit.

I was doing the effectslayout mxxr dynacomp actually

[idy]

Have Kvendekrol and Atodovax read the pages that describe the cause and treatment of switch popping?
http://www.muzique.com/lab/pop.htm
is a good place to start.

Do you know what the guys mean by "pedal ventriloquism? Its not a joke.

Everyone is telling you it is not inherent in any circuit or any (correct) layout. But a leaky cap will sabotage any switching arrangement. And a bouncy switch will add noise to any circuit. And another pedal (or active guitar, or amplifier) leaking DC will sabotage other pedals around it.

[Atodovax]

Have Kvendekrol and Atodovax read the pages that describe the cause and treatment of switch popping?
http://www.muzique.com/lab/pop.htm
is a good place to start.

Do you know what the guys mean by "pedal ventriloquism? Its not a joke.

Everyone is telling you it is not inherent in any circuit or any (correct) layout. But a leaky cap will sabotage any switching arrangement. And a bouncy switch will add noise to any circuit. And another pedal (or active guitar, or amplifier) leaking DC will sabotage other pedals around it.

Well i did read that and other articles... See i´ve already tested at the output and the input of the effects and i see 0 mv.. Nothing.. Also, i tried disconecting the IN and OUT from the 3pdt and added 1uf capacitors in each conection series to the switch with 1MEG resistors to ground, again NOTHING. I also tried with no LED, also nothing better. What DID reduce a little bit the "click" or "POP" was using a lighter swtich but i always use the same kind of 3pdt switches and this "POP" is the kind you would expect with a leaky input or output cap or an effect with no PULLDOWN resistors. The 1uf capacitors i tried where ceramic multilayer so im really stumbled here... Should i decouple every +9v conection on the pcb with caps and resistors? i dont think the original pedal has this, at least it seems this layout is following the original schematic.. Very strange... I also tried with different CA3080s. If anyone could confirm that the Effectslayout is working that would be great. Also i tried the pedal alone, with the enclosure, with battery and with PSU. Always the same switching noise that is reduced when the VOLUME knob is turned down. I did find a partial solution to the problem using a 2k resistor from the Output to ground but obviously that lowered the volume a lot and the pedal lost almost all the high end.

[ElectricDruid]

Does the "partial solution" mentioned above suggest that the circuit itself might be producing the DC? And if that's so, why? It seems like many other people have built these pedals without problems, so perhaps we need to be looking for what the particular fault is in this particular build/builds? Could there be some common cause? Or do two different builders have similar issuers with different causes? (also not impossible, just marginally less likely).

No bad reflection on either of you, Kvendekrol or Atodovax...just trying to get to the bottom of where the problem lies.

T.

[Atodovax]

Does the "partial solution" mentioned above suggest that the circuit itself might be producing the DC? And if that's so, why? It seems like many other people have built these pedals without problems, so perhaps we need to be looking for what the particular fault is in this particular build/builds? Could there be some common cause? Or do two different builders have similar issuers with different causes? (also not impossible, just marginally less likely).

No bad reflection on either of you, Kvendekrol or Atodovax...just trying to get to the bottom of where the problem lies.

T.
Thanks for replying.. Its strange that we are percieving the same syntomps using the same layout, but i have built dozens of pedals using effectslayout and they all worked great. i wonder if my Multimeter is not reading DC and thats why i think its not there

[Atodovax]

Ok so after changing the 3pdt switch for the third time. Now i realize that the "POP" is only audible when im playing the guitar. If i click on the switch with the guitar volume turned down, i dont have any click. not even with the pedal maxed out. But if i play a chord and let the strings ringing while i push the switch (with the pedal set loud enough) i can definetly hear a loud "POP" with the obvious increase of volume and gain that the effect provides. As if the POP was only acting when there is "guitar sound flowing through the pedal" ha ha ha

[Digital Larry]

I don't have any experience with this circuit, but it would be interesting, if you can get a scope (everyone should have a scope) to see what is really causing the pop.  Seems like everyone is assuming that it is due to a difference in DC offset, but as you mentioned, a compressor with no signal coming in is going to be at the maximum gain and then suddenly it gets connected and it's going to take awhile to respond to that input transition (which like as not, did not occur at a zero crossing of the guitar signal).

I don't want to be controversial but it seems like a compressor might NOT want to be 100% true bypass for just this reason.  A FET input buffer would likely not load your guitar in any noticeable way and the compressor circuit would still be responding to your playing.