Why is my plate amp failing?

[icor1031]

I have had two plate amps now, die in the same way.
It's not a ground issue, as the second amp does not have a ground plug.

The first was SA 240W, the second was SPA 250W

What happens is that after X time, in the first case I think a few months, in the second case about 2 months, it starts playing audio to my sub that sounds like blowing air, or sizzling bacon.

It does this even with the signal line disconnected.

Also, it gets worse over time, once it starts. - becoming louder, but primarily more frequent.

Here's a video, if you can make out the sound.. There's a constant noise, that sounds like static - that's my camera. Ignore that noise.
The other noise you hear, that sounds similar to my description above, is what's coming through my sub.

Any ideas? (Taken using a panasonic omni mic capsulate.)

http://www.youtube.com/watch?v=D7jhjQy4G5M

((If related, it should not be a ground issue any more for this reason as well: The wiring was re-done. The ground was separated from the neutral in my apartment's breaker box, which is a sub breaker box (the parent's is still shared, as I'm told it should be.) .. Also, my ground is now my own, and not shared: I have put in TWO ground rods for my apartment.. Last, I know it is significantly improved, because my computer no longer restarts when I touch it - an issue I previously had.))

[Psycoacoustics]

I have had two plate amps now, die in the same way.
It's not a ground issue, as the second amp does not have a ground plug.

The first was SA 240W, the second was SPA 250W

What happens is that after X time, in the first case I think a few months, in the second case about 2 months, it starts playing audio to my sub that sounds like blowing air, or sizzling bacon.

It does this even with the signal line disconnected.

Also, it gets worse over time, once it starts. - becoming louder, but primarily more frequent.

Here's a video, if you can make out the sound.. There's a constant noise, that sounds like static - that's my camera. Ignore that noise.
The other noise you hear, that sounds similar to my description above, is what's coming through my sub.

Any ideas? (Taken using a panasonic omni mic capsulate.)

http://www.youtube.com/watch?v=D7jhjQy4G5M

((If related, it should not be a ground issue any more for this reason as well: The wiring was re-done. The ground was separated from the neutral in my apartment's breaker box, which is a sub breaker box (the parent's is still shared, as I'm told it should be.) .. Also, my ground is now my own, and not shared: I have put in TWO ground rods for my apartment.. Last, I know it is significantly improved, because my computer no longer restarts when I touch it - an issue I previously had.))

After changing my Comcast modem to one that included the phone option, I developed a hum in my system.

I don't know if what you have is a hum,,,, but if you get the noise without it connected to the stereo??? Than it must be comming form the wall, right? My stuff is already plugged into a "Audioprism power foundation 3", that
Obviously wasn't enough.

I went to Guitar Center And bought a "Hum X" plugged my cable box into it and,,,it worked!

Buy a "Cheater plug", put it between your cable box and the wall, see if the noise goes away.

Good luck! Mark

[icor1031]

It's not a hum mate, but thanks. Check out the video.

After changing my Comcast modem to one that included the phone option, I developed a hum in my system.

I don't know if what you have is a hum,,,, but if you get the noise without it connected to the stereo??? Than it must be comming form the wall, right? My stuff is already plugged into a "Audioprism power foundation 3", that
Obviously wasn't enough.

I went to Guitar Center And bought a "Hum X" plugged my cable box into it and,,,it worked!

Buy a "Cheater plug", put it between your cable box and the wall, see if the noise goes away.

Good luck! Mark

[dthomas]

Your computer restarting when you touch it sounds like a ground loop. Not sure what you mean by 2 ground rods but two seperate ground locations is not the best idea as it can promote ground loops and the circulating current they can develop. It is best to have one single ground that everything is attached to. Couple of other things is to see if you have a defective component in your system. You can do this by disconnecting all inputs and outputs from each device CD Player, Receiver, Amp, Cable Box etc... and plugging them into the AC volume and gain controls set to minimum see if you have a high DC or AC signal present on any of the devices. The output of a CD player can be as prone to high DC offset as a high powered amplifier can and this could be damaging the devices it connects to or at a minimum causing noise.

What part of the world are you in? Are you using a step down transformer that may be starving it for current?

[killa]

He uses "mate" a lot so he is probably australian

[dthomas]

Yeah but the Irish and Brits using mate a lot also.

[icor1031]

I am from USA, but I used to play with Anzacs..

Thanks for the information. Do you mind clearing a couple of things up for me?

I'm confused.. Are you saying that my cable box being plugged into the outlet, can damage my sub amp? ... and to disconnect every thing else, and plug the cable box into my sub amp instead of my receiver to see if it creates noise?
Because if that's so, then I think "any" device in the entire house could cause that. So, I assume I have misunderstood.

Also, I only mentioned the ground in case it can be an indirect cause. The sub amp I have now does not use a ground prong. Also, my ground is "much better" now, because my PC does Not restart when contacted, etc... Is the ground still an issue?

I'm not using a transformer.

Good evening.

Your computer restarting when you touch it sounds like a ground loop. Not sure what you mean by 2 ground rods but two seperate ground locations is not the best idea as it can promote ground loops and the circulating current they can develop. It is best to have one single ground that everything is attached to. Couple of other things is to see if you have a defective component in your system. You can do this by disconnecting all inputs and outputs from each device CD Player, Receiver, Amp, Cable Box etc... and plugging them into the AC volume and gain controls set to minimum see if you have a high DC or AC signal present on any of the devices. The output of a CD player can be as prone to high DC offset as a high powered amplifier can and this could be damaging the devices it connects to or at a minimum causing noise.

What part of the world are you in? Are you using a step down transformer that may be starving it for current?

[Psycoacoustics]

I am from USA, but I used to play with Anzacs..

Thanks for the information. Do you mind clearing a couple of things up for me?

I'm confused.. Are you saying that my cable box being plugged into the outlet, can damage my sub amp? ... and to disconnect every thing else, and plug the cable box into my sub amp instead of my receiver to see if it creates noise?
Because if that's so, then I think "any" device in the entire house could cause that. So, I assume I have misunderstood.

Also, I only mentioned the ground in case it can be an indirect cause. The sub amp I have now does not use a ground prong. Also, my ground is "much better" now, because my PC does Not restart when contacted, etc... Is the ground still an issue?

I'm not using a transformer.

Good evening.

I think what he means is,,,, unplug everything from the wall. Than start plugging everything back in one at a time while listening for the noise. I'd start with the sub, than the receiver, etc. Make sure everything is turned off while your plugging and unplugging. In other words plug in the sub, turn it on, listen, turn it off, plug in the next piece, turn it on and the previous piece, listen, and so on and so on until you find the offending component.

Also I would never plug anything into the outlets on the back of the receiver, I'm just weird like that. Or the sub for that matter. Any power amp has to go right to the wall, IMO.

I would also make sure that the outlets are wired correctly. Most home centers sell a small plug with lights on it to tell you if all is well.

You say the amp is failing,,, is it? Or is just noisy! Things like this can be pretty hard to track down sometimes. You may not have a ground loop, or a ground loop induced hum, but you do have some kind of noise! Plugging stuff in one piece at a time should point you to the offending piece.

Good luck and let us know what you find. Mark

[WernerM]

Is there anythig around the sub that is wireless? One thing that could be happening is that you are getting digital noise that is interfering with the amp. This can be related directly to the amps, but for 2 of them to be doing the exact same thing in such a short period is odd. I once had a computer speakers that would sound like that if my cell phone was to close to it. Every time I would get a phone call, it would emit static popping noises. That said, it also makes me wonder if somehow there is an issue with the sub itself. Maybe some sort of magnetic radiation that after time starts affecting the amp. Not very likely, I don't think, but anything is possible. The idea of disconnecting everything electronic near it, and leaving only the sub plugged in is good trouble shooting advice. If it does it when there isn't anything electrical near it to cause interferance (possible radiation), then you know it is in either the amp, bad sheidling of the wires in the enclosure, or a loose terminal on the sub, or in the sub itself. It would probably be easier just to take the sub to another room, or even to another location on different power. This way you don't have to unplug a lot of components, and you are also eliminating the outlet, or power contained in your apartment. Just my 2 cent's. I know some of this may sound waaaay crazy, but you would be amazed what I have found diagnosing digital noise in networking

[awwnuts]

All are off the mark. Nothing external causes this sort of noise.

The sounds you are hearing are the result of inferior (and probably counterfeit) transistors somewhere in the amp. Probably the input stage - either the diff amp or the muting circuitry. It can also manifest itself in the preamp stage, specifically in the op amps.

No matter how you slice it - it's internal to the amp.

[dthomas]

One I mean is disconnect everything and use a VOM to measure the output of each RCA jack with not input. What you are looking for is a DC voltage or an unusual AC voltage on the RCA jacks. Specifically the output of your receiver that feeds your plate amp directly. One of the devices supplying line level signals to your plate amp could be defective and could be causing your plate amp to fail. Actually this is probably more likely than a ground issue.

Also leaving your plate amp powered on have you tried to shut off individual pieces of gear seeing if one in particular is associated with the noise?

When you have 2 ground references it can be a bad thing especially if one is closer to earth than the other. It can can cause small currents to circulate on the ground line and introduce noise onto electronic equipment. So it could be a direct cause of your failures. Best solution is a single well done ground that all devices are referenced too at the service panel. Also having all your A/V gear on the same circuit is very beneficial as they will have the same reference to ground.

I listened to your video all I heard was noise. When you say your plate amp fails does it actually quit working at some point? Or are just hearing this buzzing/crackling noise? If the latter is the case than any of the devices feeding line level and even digital signals for that fact could be defective and sending the noise to your plate amps input.

[dthomas]

Yeah maybe but he has had the same problem on 2 different model sub amps. Doubtful they both have sub standard silicon in them. I think he has a failed device in the audio chain feeding the sub amp noise.

[awwnuts]

Not doubtful at all. The two models the OP discusses are actually the same basic amp.

If it was a source feeding the amp, then you wouldn't hear high frequency noises due to the non-defeatable low pass filter.

Source: I've repaired hundreds of these.

[Whitneyville1]

Icor's computer is close/part of his audio system. I can't pick on Dayton/P-E for these issues only. A-N makes a strong (and one I can vouch for) case for EMI/RFI, and Dave, you're grounding question points to a similar issue. Icor's apartment had wiring issues, especially relating to grounding. "Junk" in the common mode on the power lines is becoming more and more common today from microwave ovens, baby monitors, cordless phones, hair dryer motors, even the new "energy saver" inverter A/C units, and of course 'puter-thingey-type stuff. "Cleaning" power line voltage isn't easy and can get costly at times. Living over/near a welding shop with 'puter's, you better have LOT'S of copper sheeting grounded (mu-metal) with BIG air-wound coils and extremely high-voltage oil-filled caps to discharge the corona.

[Tin_Ears]

Bad press-on connection? Bad solder joint? Failing VC wire?

[scottq]

Is there anythig around the sub that is wireless? One thing that could be happening is that you are getting digital noise that is interfering with the amp. ... I once had a computer speakers that would sound like that if my cell phone was to close to it.

No, the noise in the video is not cell-phone interference noise; see here for an example. I find this much more common with GSM devices (than CDMA - occassional but very rare and much quieter) based on my experimentation.

The sounds you are hearing are the result of inferior (and probably counterfeit) transistors somewhere in the amp. Probably the input stage - either the diff amp or the muting circuitry. It can also manifest itself in the preamp stage, specifically in the op amps.

No matter how you slice it - it's internal to the amp.

Ding, ding, ding! I believe you are correct, sir (or ma'am?). I would guess output devices...

Certainly, frustrating for it to happen twice in a row. But with large lots of transistors purchased and inventoried at a time, it's entirely possible.

Do you run your amp/sub hard? Stressing the transistors will bring out failures much quicker than "light" usage.

[awwnuts]

No, the noise in the video is not cell-phone interference noise; see here for an example. I find this much more common with GSM devices (than CDMA - occassional but very rare and much quieter) based on my experimentation.

Ding, ding, ding! I believe you are correct, sir (or ma'am?). I would guess output devices...

Certainly, frustrating for it to happen twice in a row. But with large lots of transistors purchased and inventoried at a time, it's entirely possible.

Do you run your amp/sub hard? Stressing the transistors will bring out failures much quicker than "light" usage.

Definitely a guy. Also, output devices are far too low-gain to produce such subtle effects. An output device generally avalanches quickly and shorts B-E or C-E. The result is either lots of distortion or speaker-cooking DC.