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Old 01-01-2013, 07:26 AM   #1
ville525
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Question Loud pop from amp

Hi! I have an old Marshall 5210 (solid state). The problem is that it pops really loud when i turn it off, kind of like a gunshot. Does anyone know why this happens? It doesnt matter if the volume is on or not. Neither if its earthed or not. It works great otherwise, the popping is just really annoying.

I've heard you could add a switch between the power source and the speaker, does anyone know if this works (and is safe)? Or is there any other solution?
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Old 01-01-2013, 07:39 AM   #2
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I used to have this issue with my Matamp. When I had it serviced I asked the tech to check it out. Turned out it was nothing bad, couldn't remember the exact thing that caused it, but he said it was harmless. IIRC he put a resistor between the switch and something else to reduce the noise, but it was still there.

If you're still concerned about it, have a tech look at it for you.
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Old 01-01-2013, 10:57 AM   #3
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Turn down the volume before you turn it off. This is normal for some amps. Not sure I'd add the switch between the output and speaker. If you happen to forget to turn it back on, you might damage the amp.

The popping you're hearing is nothing more than the voltages from the power supply collapsing. As those voltages collapse, the preamp and amp circuits also begin to collapse and an abrupt signal gets sent to the speaker. The coil of the speaker then generates a flyback voltage, which is being shot back into the amp. Like I said, turn down the volume and it may go away.
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Old 01-04-2013, 07:45 AM   #4
ville525
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Quote:
Originally Posted by KG6_Steven
Turn down the volume before you turn it off. This is normal for some amps. Not sure I'd add the switch between the output and speaker. If you happen to forget to turn it back on, you might damage the amp.

The popping you're hearing is nothing more than the voltages from the power supply collapsing. As those voltages collapse, the preamp and amp circuits also begin to collapse and an abrupt signal gets sent to the speaker. The coil of the speaker then generates a flyback voltage, which is being shot back into the amp. Like I said, turn down the volume and it may go away.


It doesnt matter if the volume is off, or even if i plug in headphones. But how would a switch damage the amp?

/Sorry for late reply
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Old 01-04-2013, 08:04 AM   #5
Offworld92
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That's normal.

Does your amp have a standby switch? If so turn that off for a minute then turn off your power, that should prevent it from happening.

But it's not a big deal either way.



On this subject, does anyone have a link to a article or something detailing technically why this isn't a big deal. My audio tech friend got pissed off at me when I turned my amp off saying how it was terrible for the speakers, and we got into a mini argument over it. It'd be nice to show him up.
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Old 01-04-2013, 08:09 AM   #6
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Quote:
Originally Posted by ville525
It doesnt matter if the volume is off, or even if i plug in headphones. But how would a switch damage the amp?

/Sorry for late reply

It would disconnect the speaker from the amp, which is bad, Amps need some form of resistance between the hot and the ground, otherwise it can damage the amp if it is on while the speaker is out of the circuit.
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Old 02-07-2013, 04:49 AM   #7
idioot28
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I recently serviced a 5210 for a friend, it had the exact same problem. It is normal to hear of soft pop when turning the amp on and off. But just before the off-pop it gave a loud bang, as you discribe, like a gunshot.
This is due to a sudden voltage change (voltage interruption which causes a sharp rise in voltage) when turning off. The rc snubber provides an alternate path for this current to flow so it won't damage anything in you circuit.

Basically the rc snubber consists of a cap and a resistor.
I put 2 snubbers on the switch, one over brown and one over blue side.
I used an X2 .1uF 250v cap and a 100 Ohm 3w resistor in series, parallel on/over the switch (on both sides)

After if installed the snubbers, the loud bang was not completely gone (if the trafo isn't a 100% anymore, there will always be a little ripple in the current) but it has been reduced by at least95%. The standard on/off plops are louder than the switch "bang" now.

Google for some examples on rc snubbers.

Good Luck!!

Last edited by idioot28 : 02-07-2013 at 04:51 AM.
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Old 02-07-2013, 04:58 AM   #8
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Quote:
Originally Posted by idioot28
I recently serviced a 5210 for a friend, it had the exact same problem. It is normal to hear of soft pop when turning the amp on and off. But just before the off-pop it gave a loud bang, as you discribe, like a gunshot.
This is due to a sudden voltage change (voltage interruption which causes a sharp rise in voltage) when turning off. The rc snubber provides an alternate path for this current to flow so it won't damage anything in you circuit.

Basically the rc snubber consists of a cap and a resistor.
I put 2 snubbers on the switch, one over brown and one over blue side.
I used an X2 .1uF 250v cap and a 100 Ohm 3w resistor in series, parallel on/over the switch (on both sides)

After if installed the snubbers, the loud bang was not completely gone (if the trafo isn't a 100% anymore, there will always be a little ripple in the current) but it has been reduced by at least95%. The standard on/off plops are louder than the switch "bang" now.

Google for some examples on rc snubbers.

Good Luck!!

This thread is a month old. I'm guessing he's sorted it.

Reported.
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