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Popping sound from Amp


Rampdog

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A Classic 30 is a tube amp. A lot of amps pop a little, so do stereos at times. I think repetitive loud pops aren't great for speakers, and it could be capacitors - just a guess.
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Originally posted by Rampdog:

Thanks Pappy, Kramer, Blues, and Geoff, and the rest of ya'. Thanks for the bumps too...ceptin' I'm startin' to bruise...

I have a lot of tube amps. One of them is a Classic 30, but no heavy "pops" on it.

 

But I had exactly the same thing on my larger amp (100w) Carvin MTS3212. The thing is, with the Carvin it has a standby switch, and the pop came when turning to standby. Now, it could be several things causing this, but IF it is the same manifestation, that means it is not in the power tubes.

 

I traded out my V1 preamp tube (the first tube in the amp, on the input) which is typically a 12ax7 or something similar. In my case the pop wasn't every single time, but was enought that I winced every time I would turn the standby on.

 

After I traded out the V1 tube (which needs no biasing or anything, it is self bias for these kinds of preamp tubes) it ALMOST never did again. Once in a great while, but I quit wincing (flinching) when I turned to stanby after that.

 

I did notice again, a little bit but not much, on my Classic 30, one thing you might try for fun, unplug the actual guitar cord into the amp first...wait a minute and then turn it off (making sure the voltages are all idle) see if that helps. If not, or even if so (since it isn't "normal") try changing out the V1 tube.

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I yahoo!ed "loud pop from amp capacitor discharge"

and had a bunch of hits about the capacitors discharging their stored power in one big go and causing the popping sound, on all sorts of amps.

 

Them's the whatchmacallits that I was thinking of.

 

Can't remember what the amp tech did to fix the problem though.

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Originally posted by Kramer Ferrington III.:

I yahoo!ed "loud pop from amp capacitor discharge"

and had a bunch of hits about the capacitors discharging their stored power in one big go and causing the popping sound, on all sorts of amps.

 

Them's the whatchmacallits that I was thinking of.

 

Can't remember what the amp tech did to fix the problem though.

This may be a myth, but I remember hearing long ago that after you switch the standby on, to keep playing until the sound fades out. I've done this from the beginning, and I don't get any pops at all.

It's not simple to be simple.

-H. Matisse

 

Ross Precision Guitars

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Usually a pop when you open a switch is caused by a small arc or spark across the switch as it interrupts the flowing current. Putting a small capacitor across the switch will fix that. Just like the capacitor in an old fashioned distributor keeps the points from burning up.

 

Try something like a .01 uF 400V capacitor attached to both terminals of the switch. If it helps but isn't enough, try one a little bigger, like a .1 uF.

"A cheerful heart is good medicine."
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I'm trading out the first pre-amp 12AX7 tube with a Sovtek 5751. It should be here today...I ordered it a few days ago. Ricochet, It pops when I turn it 'OFF' not on. And I have tried unplugging my guitar first as well as keeping it plugged in. Tried all knobs off and on. Same thing. I've even tried turning it off and running like hell out of the room...I ain't as quick as Ali...Let's see if the tube works. I'll let ya'll know after I put it in.

Again thanks all.

I forgot...also there is no standby on the Classic 30

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Originally posted by DC Ross:

Originally posted by Kramer Ferrington III.:

This may be a myth, but I remember hearing long ago that after you switch the standby on, to keep playing until the sound fades out.
Ive heard the same thing...

 

 

Someone give me a tube amp and I'll check it out ;)

Lynn G
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Maybe...but again, in real experience I had it almost constantly, changed out V1 (input preamp) and almost never get it after that.

 

There are a lot of things...the only constant is it definitely is something suddenly changing state and it is getting amplified through the circuit to the speakers.

 

It's a very easy thing to try..one could for example trade between two preamp tubes (just mark them so you can put them back) and see if it helps.

 

Also...should have asked, is the outlet you are plugging into grounded? If not, try the amp at a friends house and see if it still does it.

====================================================

Check out my original music at

http://www.soundclick.com/bands/jacker

 

"In theory there is no difference between theory and practice,

but not in practice."

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Just to mention for those that don't know...a capacitor is a kind of "temporary battery".

 

The first ones were literally two "plates" made of something like tinfoil that are rolled with up together with an insulator between the two plates. When a + and - (relative) voltage is applied they "charge up" and if you then connect them to say a light bulb, they discharge into it...they would light the light bright for a second and get dimmer as time went by.

 

The large ones (some types) are polarized so that you only ever want to apply + DC voltage to one side, and - to the negative side. If you reverse this you can blow them up.

 

The "popping" you hear is NOT a cap blowing up. It might be suddenly discharging, but I think it is more likely something else. I think in my case when the V1 tube fixed it mostly that there was some sudden shutdown of the voltage that reflected down the circuit to the speakers.

 

It might be a cap, but you ought to first try it with definitely a good ground, and maybe the tube swap just to see if it helps. If it doesn't I would take it to an amp tech.

====================================================

Check out my original music at

http://www.soundclick.com/bands/jacker

 

"In theory there is no difference between theory and practice,

but not in practice."

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I'll put this on the "Ask Myles" thread, but here is what little I do know about it.

 

Originally posted by DC Ross:

....This may be a myth, but I remember hearing long ago that after you switch the standby on, to keep playing until the sound fades out. I've done this from the beginning, and I don't get any pops at all.

The pop is caused by an output cap discharging. The reason your method works, DC, is it continues to draw power from the cap evenly as opposed to the pop heard when it discharges all at once. This can be done with the Classic 30. Simply strum your guitar while you power down the amp until the cap is drained and the sound goes away.

 

This is an effective answer to the problem (and it works on ss amps, too) but I'm hoping Myles has a relatively easy way to remedy this issue once and for all.

It's easiest to find me on Facebook. Neil Bergman

 

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fntstcsnd

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Originally posted by Rampdog:

Ricochet, It pops when I turn it 'OFF' not on.

I understood that. When you turn it off, you're opening the switch. There is current flowing through the switch, and when you open it it tries to keep flowing. Makes a little spark. You can sometimes see that happen with a light switch in your house. The spark makes electrical noise that the amp picks up. The amp doesn't quit amplifying instantly when you turn it off. A small capacitor across the open switch terminals will "soak up" the voltage surge that causes the spark.

 

You're not rapidly discharging any capacitors when you turn the amp off. They leak down gradually through any bleeder resistors, and through plate current still being conducted through the tubes till the cathodes cool off. Some amps don't have bleeder resistors, and the filter caps can hold a charge that'll zap you weeks later.

"A cheerful heart is good medicine."
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I don't think it's specific to tube amps. I have a small Peavy Transtube (solid state designed to emulate tube response) amp and it does the same thing, regardless if it's turned to vintage or modern (The manual doesn't say this but ti seems like the "modern" setting does not emulate tubes, while the "vintage" setting does).

-Andy

 

 

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Ok. But if you're correct, Riccochet, why have my amps exhibiting this issue consistantly not popped when I play the guitar while powering down? (All solid state electronics.)

 

Originally posted by Ricochet:

...Some amps don't have bleeder resistors, and the filter caps can hold a charge that'll zap you weeks later.

Yeow! I did not know that. I was thought all capacitors gradually lost their charge when input power ceased.

 

My electronics for audio teacher in college told us of a friend of his who was either injured or killed as a result of a capacitor discharge.

 

In the course of diagnostics in his job aboard a navy vessel, they had to power down room-sized capacitors for 24 hours, then place a metal tool across the leads to dissipate any retained charge before working on the circuits. (With heavy rubber gloves on, etc.)

 

He called up to the control room to be certain the circuit had been powered down and the inexperienced operator made sure it was off by switching it on, then off again, immediately re-energizing those huge caps to full power. I can't imagine what happened when he crossed that tool, shorting the circuit.

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Well, one explanation I can think of for it not popping if you're playing the guitar as you shut it off is that you're running enough gain distortion to saturate a preamp stage. If the guitar tone's at all "fuzzy," you're there, and adding a momentary noise spike on top of it's going to be pretty much inaudible.
"A cheerful heart is good medicine."
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Sometimes... but it works whether it's clean or distorted. And believe me, the level of the pops was always loud enough that it would have been noticed even with distortion.

 

(Besides, I've trained myself to isolate sounds within a mix. If it were at all audible, I'd hear it. But these were sounds anyone, regardless of training, would have noticed.)

It's easiest to find me on Facebook. Neil Bergman

 

Soundclick

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I'm not saying that you wouldn't hear the sound over the distorted (or clean) guitar sound. I'm saying that you're adding a signal peak on top of a signal that's already at or near the clipping level, so the amp simply can't make any more sound. It just clips off. And the clipping level drops as the stored voltage in the filter caps drops off.
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Originally posted by fantasticsound:

Ok. But if you're correct, Riccochet, why have my amps exhibiting this issue consistantly not popped when I play the guitar while powering down? (All solid state electronics.)

 

Originally posted by Ricochet:

...Some amps don't have bleeder resistors, and the filter caps can hold a charge that'll zap you weeks later.

Yeow! I did not know that. I was thought all capacitors gradually lost their charge when input power ceased.

 

My electronics for audio teacher in college told us of a friend of his who was either injured or killed as a result of a capacitor discharge.

 

In the course of diagnostics in his job aboard a navy vessel, they had to power down room-sized capacitors for 24 hours, then place a metal tool across the leads to dissipate any retained charge before working on the circuits. (With heavy rubber gloves on, etc.)

 

He called up to the control room to be certain the circuit had been powered down and the inexperienced operator made sure it was off by switching it on, then off again, immediately re-energizing those huge caps to full power. I can't imagine what happened when he crossed that tool, shorting the circuit.

Not only that...but some capacitors you need to KEEP a bleed to ground or even unplugged they can build up a charge! Really!

 

 

In a similar veien...things you never think much about (til you do)...I bought a book a while back, great book on home electronics projects and other. A lot of the "experiments" with electronic/electric start with using a tinfoil sheet that is just put up to your TV screen..the static electricity charges it and it can actually be used, has many volts (not many amps) and can power a homemade klanger (coil and clapper).

====================================================

Check out my original music at

http://www.soundclick.com/bands/jacker

 

"In theory there is no difference between theory and practice,

but not in practice."

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Originally posted by BluesWithoutBlame:

Not only that...but some capacitors you need to KEEP a bleed to ground or even unplugged they can build up a charge! Really!

Common electrolytic caps will partially "recharge" after being quickly discharged. The actual dielectric is the oxide film on the aluminum anode foil, and the electrolyte is conductive and in contact with the cathode, so is normally regarded as though it's part of the cathode. But when the cap's quickly discharged, the ions in the electrolyte don't have time to diffuse to equilibrium in the somewhat viscous solution in modern "dry" caps, so after they have time to diffuse a small charge will "re-form." I always leave the grounding wire (with a series resistor) clipped onto filter caps as I go to work on an amp.
"A cheerful heart is good medicine."
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