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Discussion Starter · #1 · (Edited)
Hello. I find there are a lot of posts about audible hum through speakers... this is different though. My AMPS are audible.

I'm gearing up for an install and doing some hook ups on the bench lately.
When I run my ppi pc2600.2 and pc21400.2 even at low/moderate levels, I hear some musical hums coming from the AMPS. Like buzzy music. Pretty faint, probably won't be noticeable when installed in the car. By the way, sound through the speakers is great, no issues there.

Question is, should I care or is a little hum in the amp normal or OK?
If a rotten cap or loose choke coil is causing this, I'd like to fix it instead of it getting worse and blowing up later on.

And here's what I'm gearing up for:
2 jl 10w6v2, sealed, on the pc21400
4 mids on the pc4800, tbd, thinking focal polyglass 165.
2 tweets on the pc2600, tbd.

Thanks
 

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I had one of my Class D sub amps that hummed. I cracked open the case on it and three like to find the differences. It turns out the hummer had a coil in the PS circuit that was not potted correctly. However, when it warmed up the humming would stop. It didn't track with the music. It was just a constant freq hum. I was able to pot the coil (somewhat) without removing it and it got rid of the noise. If I had to do it again I would either remove the coil completely and re-pot or just live with it. No effect on the SQ...
 

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Yeah, open that thing up and throw some high-temp non-conductive epoxy on those coils. (liquid epoxy, not epoxy putty)

Same reason some TVs/monitors have the high pitched whine - coil whine, usually from the flyback transformer in that case.
 

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Make sure to bench a different amp that doesn't hum. sometimes you can get a hum through either noise in the power line or a bad ground. If you bench is straight then it's internal.
 

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Hello. I find there are a lot of posts about audible hum through speakers... this is different though. My AMPS are audible.

I'm gearing up for an install and doing some hook ups on the bench lately.
When I run my ppi pc2600.2 and pc21400.2 even at low/moderate levels, I hear some musical hums coming from the AMPS. Like buzzy music. Pretty faint, probably won't be noticeable when installed in the car. By the way, sound through the speakers is great, no issues there.

Question is, should I care or is a little hum in the amp normal or OK?
If a rotten cap or loose choke coil is causing this, I'd like to fix it instead of it getting worse and blowing up later on.

And here's what I'm gearing up for:
2 jl 10w6v2, sealed, on the pc21400
4 mids on the pc4800, tbd, thinking focal polyglass 165.
2 tweets on the pc2600, tbd.

Thanks

The "buzzy music" caught my eye. I used to have a pioneer that did this. Even without the speakers hooked up, if I cranked the volume I could hear music in a buzzy way. Most of the time I could pick out which song was playing.
 

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Discussion Starter · #7 ·
Hey thanks for the replies.

The pc2600 pretty much plays a tune, I think you could name that tune from just hearing the amp. The volume gets louder as the output increases. I didn't notice it much when playing into a pair of bookshelf speakers but when I fired up a sub it got noticeable. I believe this was due to both the increased load of the sub and the fact that I had it crossed over for low-pass at 100hz with the sub so it was easier to hear. I like the idea about painting some high temp adhesive epoxy on the coils. Sort of reluctant to crack open the warranty sticker but that's silly, it's 11 years old after all.

I don't recall hearing any sounds from the pc4800 when I tried it before, I'll re-test it.

The pc21400 didn't seem to play as musically but had intermittent higher -pitched sounds coming from towards the power input end I think.

All 3 amps are in excellent shape cosmetically. The 2600 has evidence of install, but not abused looking. Other 2 were supposed to be new, never installed. 4800 is excellent, I'm guessing hooked up on the bench and never in a car. 21400 is brand new for sure, never hooked up from what I can tell.

My bench testing is using a 12v small toy kiddie car sealed lead acid battery with thin little 14 or 16 gauge leads. Now maybe this would stress the amp power supplies into an unhappy state but according to the voltmeter, battery volts never dip below 11.5v (because I'm not cranking them up past maybe 100 W). Battery is >12.8 at open circuit. Source is mp3 player. Speaker tests were: pair of 60w 8 ohm bookshelf in stereo & subwoofer in mono played real lightly, at 2 ohms and 8 ohms.

Thanks again. This stuff is addictive. I think about it in every waking moment. Can't wait to get it installed.
 
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