Mute popping when shutting down amp

Thread Starter

robismod

Joined Sep 22, 2015
193
I have a Fender SS Ultimate Chorus amplifier when flipping power off, unit makes a loud popping sound. Can this be muted somehow? I’ll attach a couple of schematic pics…EA2EC7E2-692F-4269-ADA0-59017FEAD820.jpeg58315271-8ABA-4252-97AD-EE56A985E74A.jpeg
 

Dodgydave

Joined Jun 22, 2012
10,585
That sounds like the discharge of capacitors via the speakers, looking at the circuit the speakers go to ground via a series resistor, has this fault suddenly occurred or has it always done it?

Does it do it with the volume turned off?
 

JohnInTX

Joined Jun 26, 2012
4,704
I have the exact same amp. It’s a beast but does have the loud pop when switching off. I’ve been in and out of the amp for various repairs and upgrades but never addressed the pop. While waiting for TS I played with it this AM:


The only way to suppress the pop completely is to break the signal path at the stereo effects return jack i..e plug in a dummy plug and isolate the power amps from the preamp/tone/effects path.
A dummy plug in the mono effects return jack (isolating the power amps from all but the chorus section) still pops but a bit less.
Volume controls, no instrument connected (which shorts the inputs) etc. have no effect.
Disconnecting at the power cord instead of the power switch has no effect (thinking a ratty power switch)

I usually have something plugged into the effects loop so it hasn’t been a bother to me but it would be interesting to persue with @robismod and you guys to see what’s going on.
 
Last edited:

Dodgydave

Joined Jun 22, 2012
10,585
I have the exact same amp. It’s a beast but does have the loud pop when switching off. I’ve been in and out of the amp for various repairs and upgrades but never addressed the pop. While waiting for TS I played with it this AM:


The only way to suppress the pop completely is to break the signal path at the stereo effects return jack i..e plug in a dummy plug and isolate the power amps from the preamp/tone/effects path.
A dummy plug in the mono effects return jack (isolating the power amps from all but the chorus section) still pops but a bit less.
Volume controls, no instrument connected (which shorts the inputs) etc. have no effect.
Disconnecting at the power cord instead of the power switch has no effect (thinking a ratty power switch)

I usually have something plugged into the effects loop so it hasn’t been a bother to me but it would be interesting to persue with @robismod and you guys to see what’s going on.

Ok so are you saying if you short out the input to the output amplifier the "POP " will be removed or suppressed..?


IMG_20221130_180351.jpg
 

Thread Starter

robismod

Joined Sep 22, 2015
193
What JohnInTx said above…I’ve read that others have done that, some say turning volume down helps, and someone had suggested building in a relay circuit of some sort to “turn off the signal to speakers for a short period”. In that vein, could a simple on-off switch be wired in to the speaker leads—turn it on to block signal, then power down? (Of course remember to turn off when ready to power up again)
 

Thread Starter

robismod

Joined Sep 22, 2015
193
What JohnInTx said above…I’ve read that others have done that, some say turning volume down helps, and someone had suggested building in a relay circuit of some sort to “turn off the signal to speakers for a short period”. In that vein, could a simple on-off switch be wired in to the speaker leads—turn it on to block signal, then power down? (Of course remember to turn off when ready to power up again)
Many others have said it’s not a big deal and doesn’t hurt anything…but it makes my nerves stand on end…LOL
 

JohnInTX

Joined Jun 26, 2012
4,704
Ok so are you saying if you short out the input to the output amplifier the "POP " will be removed or suppressed..?
Yes. And actually my quick test just opens the signal path and connects the power amp inputs to air.
@robismod It’s annoying for sure. It also scared the hell out of my grandson when he was about 2yrs and to this day runs from the room when I reach for the switch.
‘Scares small children’ isn’t a great endorsement for a musician so maybe it’s time to take a look at it.

FWIW I’ve always charged it off to the +/- 15 supply getting hammered non-symmetrically but even with that, it gets noisy as the power caps discharge and the channels change around.
 
Top