Ncore NC400 problems - pops and cuts out - help!

andrewh

Member
2012-05-02 4:51 pm
My NC400 monoblocks are acting up. They make periodic popping noises, and the left channel also mutes and unmutes itself randomly. The popping sounds are not very loud, and will come in a series at about one every couple seconds, about five to ten worth, then will go away for maybe another ten minutes. The muting happens for several minutes then spontaneously goes away for a couple more minutes, only to return. The muting may happen only after the amps are warmed up - I got an hour of two of continuous play time before the muting started happening yesterday.

The problem(s) appears to have started after we moved houses and I set my audio system back up. I'm worried I broke something because when I turned on the system for the first time, the amps were not muted, and there were moderately loud thumps and buzzes from the speakers as everything powered up. (The speakers should be fine since they are just 10" woofers with 500W continuous power handling - AE TD10S).

Upstream of the amps are: PC source, USB/SPDIF converter, SPDIF reclocker, MSB Link3 DAC, First Watt B1 preamp, Blue Jeans cables.

Does anybody know if excessive turn-on thumps and buzzing can damage the NC400 amps? If so, input stage, output stage? Should I order replacement boards, or can electrical components on the boards be replaced?

Some other potential causes I can think of include:

1) poor electrical in this new house - do I need stronger power conditioning/regen?
2) dust/loose connections in the amps from the move

I ruled out electrical interference from my other gear because I unplugged everything else from the power strip and even the input line level cable, but the popping sounds still continue. I wiggled and retightened the audio interconnects and power cables - no change. I checked and didn't find any shorts in my speakers.

I'm using two Furman power conditioners, one amp on each strip, with the rest of my components distributed across both. The system ran flawlessly at our old house for a year.

Appreciate any diagnoses or troubleshooting thoughts you may have.
 

andrewh

Member
2012-05-02 4:51 pm
Update: the popping sounds mainly come from the left channel, and happen consistently at 9am (and also randomly through the day). This makes me think the cause is some external EMI or mains power noise. I'm going to try sharing power outlets/filters with the right channel to try to rule out mains power noise.

At least I'm reassured the amp itself probably isn't damaged.
 

andrewh

Member
2012-05-02 4:51 pm
Problem solved! I plugged the left channel amp (which was transmitting the noise into the speakers) into the same power strip that the right channel is plugged into, and the noise hasn't come back.

Both power strips are plugged into the same wall jack (with two outlets), so I don't know exactly what's going on. But the wall jack looked like it had been DIY installed by the landlord, so it doesn't exactly inspire confidence. Seems like somehow it picks up noise from the power lines.