Combo amp makes noise when turned off

[Bonedoge]

I got small combo amp called PJB Briefcase, and whenever I turn it off it makes a popping noise like 'PZZzz..', even if I turn the volume all the way down before turning it off.
And actually I can see the cones are shrinking inwards when it is making that noise.

Is it serious problem? Is it severely damaging the speakers?
Or is it general with this specific model?

Please help with me even if it sounds totally dumb

 

[Bob_Ross]

At least 50% of all the amps I’ve ever used made that sound. Never was a problem.

If I’m not mistaken that sound is the result of “capacitive discharge”

…or perhaps it’s “amp farting”?

One or the other.

 

[Wasnex]

I too have worked with various amps that do similar things. Can't say if it's normal for the Briefcase. If not, there is nothing you can do to fix it, unless you know how to trouble shoot and repair electronics. Then you will most likely need a copy of the schematics/repair manual.

 

[Bonedoge]

At least 50% of all the amps I’ve ever used made that sound. Never was a problem.

Thanks a lot! That makes me feel much better.
As I have never experienced that with other amps I played with, I think I was worried too much.

 

[agedhorse]

Most amps have protection circuits designed to avoid this.

 

[SC Bassboy]

Kinda related: The thing that always got me in trouble was during teardown after a show. The P.A. system would still be bumping music while we packed up and I would turn off my amp before unplugging the direct signal coming out the back. The tubes would quickly "scream to death" at full volume through the system. So... try to remember that next time you are on stage, especially if your amp already pops through the bass speakers when you turn it off.

 

[Bonedoge]

The tubes would quickly "scream to death" at full volume through the system.

Ow.. That's absolutely dreadful.. I'll keep that in mind. Thanks for the advice!

 

[JazznFunk]

Kinda related: The thing that always got me in trouble was during teardown after a show. The P.A. system would still be bumping music while we packed up and I would turn off my amp before unplugging the direct signal coming out the back. The tubes would quickly "scream to death" at full volume through the system. So... try to remember that next time you are on stage, especially if your amp already pops through the bass speakers when you turn it off.

New band name... 'The Screaming Tubes'.

 

[Ben Clarke]

What did PJB say when you emailed them to ask about it?

 

[Ben Clarke]

Kinda related: The thing that always got me in trouble was during teardown after a show. The P.A. system would still be bumping music while we packed up and I would turn off my amp before unplugging the direct signal coming out the back. The tubes would quickly "scream to death" at full volume through the system. So... try to remember that next time you are on stage, especially if your amp already pops through the bass speakers when you turn it off.

Unless you turned your amp off within seconds, that's the sound tech's fault. 100%.

 

[Wasnex]

My GK 700RB mutes the output section when you turn the amp off. However just before it totally shuts down, you can see the woofer cone wobble a bit. I think I can trick the mute circuit into not work by cycling the amp on and off again before it totally shuts down. I don't remember specifically what it does, other than make unexpected noises. AFAIK this is probably normal as the mute circuit takes a while to reset. Not something I do intentionally.

I also have a couple of Sadowsky SA200s that let at a squeal as they are shutting down. Since both amps do the exact same thing, I assume it's normal. I can reduce or possibly eliminate the squeal by continuing to play as the amp is shutting down.

 

[ninjatanzen]

My GK 700RB mutes the output section when you turn the amp off. However just before it totally shuts down, you can see the woofer cone wobble a bit. I think I can trick the mute circuit into not work by cycling the amp on and off again before it totally shuts down. I don't remember specifically what it does, other than make unexpected noises. AFAIK this is probably normal as the mute circuit takes a while to reset. Not something I do intentionally.

I also have a couple of Sadowsky SA200s that let at a squeal as they are shutting down. Since both amps do the exact same thing, I assume it's normal. I can reduce or possibly eliminate the squeal by continuing to play as the amp is shutting down.

On my new GK 1001RB Legacy it makes a shut down noise. My old Genz Benz GBE 600 does not. Go figure @agedhorse has implemented solutions literal decades ago and new amps makers don't always take the time/effort. I still love my GK, and the GB.

 

[agedhorse]

On my new GK 1001RB Legacy it makes a shut down noise. My old Genz Benz GBE 600 does not. Go figure @agedhorse has implemented solutions literal decades ago and new amps makers don't always take the time/effort. I still love my GK, and the GB.

There is a lot of effort placed upon being player friendly like that. Been doing it for decades, the GBE-600 (which is getting close to 25 years now) has a very traditional delayed mute release on power-up and an almost instantaneous mute at power-down. Makes power-up and down close to silent. The newer class D amps do the same thing but with very different circuitry.

 

[Wyvern]

I've had a few bump on and off- usually normal.

Recent class D is silent through the cab but makes a capacitor squeal seconds after shutdown, similar to an old camera flash charge, but in reverse. Bit concerning, but it still works.

 

[ninjatanzen]

There is a lot of effort placed upon being player friendly like that. Been doing it for decades, the GBE-600 (which is getting close to 25 years now) has a very traditional delayed mute release on power-up and an almost instantaneous mute at power-down. Makes power-up and down close to silent. The newer class D amps do the same thing but with very different circuitry.

Interesting! I've noticed some/many amps seem to have a delay powering up. For whatever reason I didn't think about why this was, but it makes sense. As a consumer, it's much appreciated that the more knowledgeable designers look out for us (such as yourself).

 

[abarson]

What did PJB say when you emailed them to ask about it?

You mean, like actually contacting the manufacturer of the equipment? Contact Us | Phil Jones Bass

 

[Ben Clarke]

You mean, like actually contacting the manufacturer of the equipment? Contact Us | Phil Jones Bass

I know, it's a radical idea. But I think it's worth consideration.

 

[Bassdirty]

You mean, like actually contacting the manufacturer of the equipment? Contact Us | Phil Jones Bass

Why call/contact them, then wait (who knows how long, could be minutes, even hours), then potentially get ONE answer,
when you can post here first, get several different (and fun) answers (theories), 'almost instantly'?





I'm kidding. Relax. Just a little morning humor.



T$

 

[SC Bassboy]

Unless you turned your amp off within seconds, that's the sound tech's fault. 100%.

I always made that argument, too

 

[Five or Six]

Only time my amp would do that is if I shut it down with a bass still plugged in.