Standby Switch squeal/bark sound on Marshall or Fender

[Ampzone]

You guys ever get a Marshall or Fender amp that has a quick squeal/whistle when hit you hit standby to power down? I know some amp have some snubber like coupling caps to cut down on the pop you hear often. Here we have an amp that functions normally but kinda makes a quick whistle/squeal quickly when you hit standby, not the typical pop! If the volume is on 0 when you do this it makes not sound, but if it is above say 5-6 VOL it will do this when you hit the standby. I know you are quickly removing the power from the screens and perhaps this sudden withdrawal causes some amps to complain more than others. It's just the sound is not the usual pop or whooof!

[Jazz P Bass]

I have seen that on solid state amps.

It usually involves a failing power supply capacitor.

[nsubulysses]

I have experienced this squeel on a few Mesa rectifier series amps. I don't recall having that experience with other brands. I always assumed it was because it was such a high gain amp and some preamp tubes were slightly microphonic. I never looked into it further and was fine with my assumption because it only did it when the amp is cranked really high on volume and gain (like over 5) and you turn it off. Otherwise the amps worked normally even on a lower volume power down, as you say. I wondered if flipping the standby literally jostled the tube for a quick burst of microphonic noise before the sound cut out. just a guess

I've never heard a customer complain about this.

[g1]

I had a similar issue once, in that particular case it turned out to be lead dress around the choke area. I suppose the collapsing field of the choke was inducing the squeal in the wires.

[Ampzone]

I had a similar issue once, in that particular case it turned out to be lead dress around the choke area. I suppose the collapsing field of the choke was inducing the squeal in the wires.

It appears it is not a huge problem from what I read here. I just noticed as it was not the typical "pop" but a quick siren high pitch sound as the power is stripped away. I may take a look at the dress but otherwise I cannot find anything.
Thanks for weighing in. I may leave it alone if you guys feel its just a minor quirk.

[drewl]

Are these high gain channel switching amps?
Sometimes those will switch to the high gain channel when powering down and cause a little chirp.

If not it might just be the high voltage draining

[Ampzone]

Are these high gain channel switching amps?
Sometimes those will switch to the high gain channel when powering down and cause a little chirp.

If not it might just be the high voltage draining

In this case a Marshall super lead 100W, a squeak like chirp is a better way to describe it if you kick the standby on (removing power) at volumes 5 and up. Annoying but I remember somewhere hearing this before with other amps.

[Enzo]

Just as an experiment, leave the standby on, and instead pull the power plug from the wall outlet. Does it behave the same way?

[Ampzone]

Just as an experiment, leave the standby on, and instead pull the power plug from the wall outlet. Does it behave the same way?

Ah! good idea, I will try it.

[Jazz P Bass]

That test may help identify a power switch problem.

Or not.

[Ampzone]

That test may help identify a power switch problem.

Or not.

Test results, power off via the wall socket, no chirping. Also if one switches off the standby and power switch in tandem you get a longer chirp squeal as it dies. But yes no issue when you power off at the wall.

Strange. I will attempt to post a linked sound clip now.

You will hear the first the standby switched off, then both standby and power switched off at the same time.

https://clyp.it/hn4skao1

[Ampzone]

Test results, power off via the wall socket, no chirping. Also if one switches off the standby and power switch in tandem you get a longer chirp squeal as it dies. But yes no issue when you power off at the wall.

Strange. I will attempt to post a linked sound clip now.

You will hear the first the standby switched off, then both standby and power switched off at the same time.

https://clyp.it/hn4skao1

Did the clip play for you guys?

[Jazz P Bass]

Yes it did.

Odd noise.

Have you pulled any tubes.

I would start with the preamp.

Power tubes, one at a time.

[Ampzone]

Yes it did.

Odd noise.
The
Have you pulled any tubes.

I would start with the preamp.

Power tubes, one at a time.

I know, it's weird! I will try removing v1 and so on and see where it stops. Otherwise it plays normally
On the road now so it will be a couple days until I can try the test.

Maybe tne bias supply is injecting some junk?

[pdf64]

What's the amp? Schematic?