My empeg has a problem now when it has been running for a while. The rear RCA outputs start to emit a random scratchy / whooshy sound that is quite loud over the music. If I switch the front and rear RCAs, the sound moves to the front speakers. So it's something about the rear RCA outputs.

Anyone else experience this? It must be some hardware problem, any guesses where I should start looking?

The traces on the PCB at the RCA jacks could have hairline fractures. That's one idea.

Another possibility is the player *might* be lacking the "capacitor mod". Is it a Mk2, or a Mk2a?

Thanks for the reply. It's a Mk2a. What's the capacitor mod?

A Mk2a should be fine -- the capacitor thing was for Mk2 units: removing a couple of caps from the PCB improved high end response, or something like that.

Scratchy sound is more likely to mean "bad connection", either in the docking connector, or the wires that connect that to the PCB, or perhaps a cracked trace on the PCB.

Since you said it happens only after things have warmed up, I'd bet more on the PCB.

Something in the recesses of my memory wants to say that this is one of the numerous issues that can come about from the faulty IDE headers (cold solder joints). I seem to remember it being reported before and thinking that it was odd that the IDE header could affect music playback in that way.

Then again, perhaps my memory is just rubbish.

Wouldn't hurt to check it carefully though. Both of the units I had eventually developed problems with the IDE headers.

Do you have a tuner? Does the same sound occur over tuner (or AUX input?)

I have had the IDE header problem, but touching up the solder joints seems to have fixed that. In my case, I'm not streaming my music from the hard drive (which is actually a CF card) but rather from the Ethernet port, using my custom player software. The front outputs are fine, just the rear are acting up. I don't have a tuner.

I've looked at the PCB and can't see anything obviously wrong. I'm going to touch up all the related solder joints and I think I'll replace those BB INA2137UA op-amps for good measure. If the op-amp was ESD zapped I'd think it could have this problem, too.

I tried wiggling the unit in the dock while the noise was happening, and no change. I also cleaned the dock connector with a little DeoxIT.

For now I've put in my spare empeg (always good to have a spare!) and it's been working fine.

Thanks for the help guys, I'll let you know how the resolder / op-amp change goes.

I agree that the symptoms you describe make it sound like a hardware problem, such as the aforementioned broken traces, or maybe a bad op-amp or bad capacitor. The fact that the audio problem is only on one of the two pairs of outputs should (under normal circumstances) be a dead giveaway that the problem is entirely in the output stage of the audio hardware.

HOWEVER... you *are* running custom software. And the DSP on the empeg is controlled by software. And the front/rear outputs do have features that are DSP controlled. So if you can't find anything wrong with the hardware, I'd say, see if the problem reproduces by running a regular player build.

Doh! Somehow I missed that in the original post. Ignore my post. Good luck finding the problem.

Well I touched up the solder joints, and replaced the BB op-amps, at $5/ea. Now another channel is scratchy! But it happens all the time now, and I found the culprit. It's the little EMI filters right before the analog connector. I can't find the exact part, but I think these should work:
http://search.digikey.com/us/en/products/MEM2012P10R0/445-3362-1-ND/1473648

Looks like it's fixed. The replacement filters are a little smaller which made soldering tricky, but they work fine.

Nice work!