Pedal pops just on some amps

[Lino22]

The T-Rex fuzz pops both ways.

[duck_arse]

have you ever tried the millenium bypass? it can still be used with a 3 pole footswitch, easy peasy. and with a wrong diode on the gate pull-up, you can get slow turn on of the led.

[Lino22]

I will try that!

[Rob Strand]

The T-Rex fuzz pops both ways.

A commercial pedal doing the same thing can't be blamed on any layouts or wiring issues.   It has to be part of a larger scale problem.

Are you using the same power supply for all your testing?

What if you power the T-rex from battery via the DC jack (be careful of polarity)?

Could the amp have a fault?  Try different cables?

[Lino22]

I can hear a 50Hz hum from my amp, this is an old apartment house and the electricity is probably not perfect.
It definitely can be part of the problem. I will test the T-Rex tomorrow again, fed from a battery.
Also - the click seems to get louder when i place a pedal after the tested pedal (Ibanez DE7, T-Rex fuzz).

So if you grab one of your 3PDT wired pedals and test it on an amp with both preamp and master all the way up, it won't click?
I test it: Les Paul with volume down > pedal >VOX AC15.

I am gonna also test the Millennium 1, just soldering it up.

[Rob Strand]

If you have any non true-bypass pedals like Boss or Ibanez (past 1978), configure the following:

Guitar -->   Pedal under test -->  Non true-bypass pedal --> Amp

Set the non true bypass pedal to bypass and power from battery.    What this does is basically buffers the amp from all the switching.    If your amp has DC leakage at the input and you use true-bypass pedals what happens is the impedance on the signal changes between effect and bypass.   The small DC current leaking from the amp will have a different DC offset at the amp in effect and bypass mode so when you switch between the two you get guaranteed ticks.  *However*  given you were able to reduce the problem by manipulating the LED current  I don't think this is what is going on.   Just the same the set-up puts up a barrier for that case.

Next run the pedal under test from battery and see what the results are.

You can get weird problems sometimes when the shielding or the earth connections to the bridge on your guitar aren't good.    If you have a spare bare 6.5mm jack, solder the two pins as a short then plug it into the input of the pedal under test then see if you get any click.  That takes the guitar and cables completely out of the picture.

My gut feeling is you amp has something funky going on with the mains grounds (either by design of by fault) or there's something weird going on with your power supplies.

The more things with potential to cause issues you can removed (guitar, cables, PSU) the more chance you have finding the problem - basically because there's not much left in front of you that can go wrong.

FWIW,  I doubt the Millenium circuit will solve anything.   You have already established the LED current is the/a cause.    The LED current will still be flowing with a Millenium circuit.   In fact the main motivation for the Millenium circuit is to simplify the switching/switch.   By design it is known to have the possibility of creating clicks and the all the circuit maneuvering  with diodes etc is about keeping that low, not removing it.

http://www.geofex.com/Article_Folders/Millenium/millen.htm
Another extreme test would be to have your LED circuit  completely isolated from the pedal and power the LED from its own battery.  Basically it would be a completely separate circuit with it's own power which just happens to live in the same box as a pedal and uses the same switch.  No connection between the pedal ground and the LED 0V.   If that changes something then you have to start looking at the switch.  Some sort of extreme capacitive coupling or a fault.   If the metal mounting parts of your switch are not grounded it's possible to get weird capacitive coupling through the switch.

[Lino22]

Another extreme test would be to have your LED circuit  completely isolated from the pedal and power the LED from its own battery.  Basically it would be a completely separate circuit with it's own power which just happens to live in the same box as a pedal and uses the same switch.  No connection between the pedal ground and the LED 0V.   If that changes something then you have to start looking at the switch.  Some sort of extreme capacitive coupling or a fault.   If the metal mounting parts of your switch are not grounded it's possible to get weird capacitive coupling through the switch.

I was thinking about this, to feed the LED from a separate DC. I am dead sure it would help. The stomp switch metal mounting parts are grounded, i have just tested it.
I use a metal enclosure and all metal mounted pats are touching the metal. I do not use isolated jacks, so they are grounded via the enclosure. I was afraid of a ground loop if i wired the jacks grounds together, so i left the output hanging on the enclosure.

[Lino22]

If you have any non true-bypass pedals like Boss or Ibanez (past 1978), configure the following:

Guitar -->   Pedal under test -->  Non true-bypass pedal --> Amp

I did it

Also - the click seems to get louder when i place a pedal after the tested pedal (Ibanez DE7, T-Rex fuzz).

But i will do it again tomorrow and feed it from a battery.

[Rob Strand]

I was thinking about this, to feed the LED from a separate DC. I am dead sure it would help. The stomp switch metal mounting parts are grounded, i have just tested it.

Quite possible.   It's not solving the real problem though.   There's something totally whacked somewhere for things to behave like they are.

I use a metal enclosure and all metal mounted pats are touching the metal. I do not use isolated jacks, so they are grounded via the enclosure. I was afraid of a ground loop if i wired the jacks grounds together, so i left the output hanging on the enclosure

It's certainty reducing the list of possibilities.

Maybe the input and/or output jack grounds aren't connecting properly.  Try connecting the output jack to another ground.  Try a number of ground points you have nothing to lose.

But i will do it again tomorrow and feed it from a battery.

See how you go. What often happens with these crazy/frustrating types of problems is something you think is normal/correct turns out not to be so normal.   It's very hard to find.

[PRR]

Don't open the LED, short it.

[Lino22]

I see what you mean ... there will be less current shift.

[Rob Strand]

I see what you mean ... there will be less current shift.

It was already mentioned here,
https://www.diystompboxes.com/smfforum/index.php?topic=131618.msg1279844#msg1279844

It's not solving the problem it just burying the problem (perhaps only for now).

You can switch between a visible external to the box and second LED inside the box.   That means current doesn't change.   You can also feed the LED with a constant current source then short the LED with the switch.

https://www.electroschematics.com/led-constant-current/

IMHO, all crap solutions (because they aren't solving the real problem).

[Lino22]

Rob, i will make the testing as you suggested and post it here. Also, my December project you helped me with - the calibration square amp - is coming together and i should be able to bring results next week.
Thank you for your help i very appreciate that. I understand the problem is hiding somewhere. To help me stay better in the picture, i would like to ask if anyone can do the same thing as me

1. Turn both pregain and master on your amp all the way up.
2. Connect a (preferably home made) pedal that uses 3PDT true bypass + LED switching between your guitar and the amp.
3. Turn the guitar volume down.
4. Switch the pedal a few times there and back and check if it pops.

[Lino22]

I have tested the T-Rex pedal fed from a battery and with a shorted input jack. A very loud pop there and back.

I found out there is something suspicious going on with the input socket on my amp though. I will open and resolder it today. I thought it was a bad grounding in my apartment, because the buzz it produces reminds me of a ground loop, but when i wiggle the input socket the buzz gets barely audible.