Speakers popping and static noise at all volume levels PPI Amp - diyAudio
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Old 16th November 2008, 01:47 PM   #1
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Default Speakers popping and static noise at all volume levels PPI Amp

Hello everyone, I'm new to this forum because I've recently had some problems with my amplifier (I'm assuming it's the amplifier) and I've been searching around this forum for some answers. I can't seem to find any other threads with a problem quite like mine.

I have a PPI PCX-4125 amp and recently I've had static in all 4 speakers that is the same loudness at all volume levels, and it's somewhat random, usually when first turning the amp on. It seems to calm down after the amp warms up a bit. The other problem that started at the same time was a loud pop from my rear speakers when I turned the amp off.

Does anyone have any ideas where I can start looking to fix these problems? I'm a recent electrical engineering graduate so I have a basic understanding of most electronics, I just don't know much about amplifiers and without a schematic I don't know where to start looking.

I've taken the amp apart and checked for cold solder joints and any obviously burned parts and can't seem to find anything obviously wrong with it.

Any help would be greatly appreciated!

Thanks.

--Mike
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Old 16th November 2008, 02:36 PM   #2
ppia600 is offline ppia600  United States
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Sounds like one or more of your speakers' terminals is touching ground somehow. Maybe one of the rear? Are any of your speakers made by kicker? They had a problem with internally shorting to their frames and causing issues like that. It could also be a lack of ground connection of the rca jacks at the deck side (inside the deck, maybe a burned or cracled rca ground trace)
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Old 16th November 2008, 04:01 PM   #3
jol50 is offline jol50  United States
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I agree, RCA or speaker grounding issue. Also check the ground on amp RCA plugs. That will have resistor in it to 12v ground usually, but if it has nothing or nothing when moved then that is problem.
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Old 16th November 2008, 05:39 PM   #4
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I am running MB Quart PCE-216's in the rear and QSD-216's in the front, I forgot to mention that I have recently blown one of the front speakers I believe with a combination of loud rock music and poor tuning on my part. I found out the hard way that these two speakers sound so drastically different that it is VERY difficult to tune them and actually make them sound good with one general EQ for both sets of speakers. I don't know when this happened, but it could have happened around the same time this problem started, I haven't taken the door apart to look at it yet. Another set of PCE-216's will be replacing the blown Q's up front in my near future.

Speaker terminal grounding was the fist thing I checked when this all started. Although I just simply checked for continuity between the speaker wires (@ amp terminals) and ground when I did it. I will dig in a little more this time and I'll post back to let you know what I find.

Thanks for taking the time to respond!
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Old 16th November 2008, 06:28 PM   #5
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If you have 12dB/oct crossovers and have an open speaker, that can cause problems for some amps. At the crossover point, the impedance is near 0 ohms when there is no speaker load on the crossover.

When troubleshooting a problem like this, you should disconnect all speaker wires from the terminal block of the amp and test the amp with a known good speaker and a short length of speaker wire (that's run directly from the amp to the speaker).
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Old 17th November 2008, 02:46 AM   #6
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Ok, I checked the grounds today and everything seems fine. I also checked the impedence of all my speakers and they are all 4 ohms.

I checked between the RCAs on the amp and the chasis ground and there is (I can't remember exactly) but somewhere between 9 and 14 ohms there.

There is about 1.5 ohms between the RCA ground on the head unit and the chasis ground. (Checked at the end of the RCA cables in the trunk, not right at the head unit.)

I also tried a known good speaker and switched the input to another source using different RCA cables and the static noise is still there. In fact, the static is there even with no source plugged in and just one speaker (known good one) plugged in.

The part that throws me is how random the noise is, it is the worst when the amp is first turned on, it gets better as it warms up. It goes away for a while but will always come back at random times while the amp is running.
The times when the noise is at its worst, is usually after running the amp hard and then turning it down, or running it hard and then shutting it off, when you turn it back on you will be greated with an earfull of static.

If it would help out, I could record the noise it makes and post a link to a .wav file for people to listen to it. It sounds pretty strange to me.

Thanks again for the help everyone, I really appreciate everyone taking time to read all of this and give me advice.
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Old 17th November 2008, 04:03 AM   #7
jol50 is offline jol50  United States
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Sounds like an old stereo with a volume pot full of dust.
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Old 24th November 2008, 08:13 PM   #8
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Any other ideas on this problem? Is there anything other than a ground short that would cause this problem? If not, what about the loud pop I get every time I power down the amplifier? These two problems started at the same time so there has to be some common problem causing them both.

The amp has the same problems on a bench with all known good components hooked up so I know the problem is in the amp. My next step is to completely dissassemble the amp and check for any components that look discolored and try replacing them. I have no idea what can cause these symtptoms but if I find anything obvious I will post on here what I find just in case someone else has a similar problem.
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Old 24th November 2008, 08:18 PM   #9
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possibly bad solder joints on the board somewhere, or bad caps. Can you remove the board and have it reflowed in a electronics rated reflow oven somewhere local. Should only take 5 minutes to reflow and 1 hour cool down.

On a easier note try a heat source like a small blow dryer, and or some freeze spray on the amp in small areas looking for the fault....
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Old 24th April 2009, 02:21 PM   #10
pcaioo is offline pcaioo  Hong Kong
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have you fixed your problem?? My PP 4125 also got the same problem . but only 1 of the 4 channel.,
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