2. amps-preamps
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Electrical buzzing sound, or else I'm imagining it

For about a year now I've either had an intermittent problem or an intermittent psychosis, and it's turning out to be really difficult to tell which one it is:

The sound from my system is often dry, reedy, really unpleasant -- even my girlfriend can hear it -- and the problem seems to be of an electrical nature. There's a sort of a buzzing noise through the upper midrange and low treble -- sort of the audio equivalent of those little trickles we used to see on the television when dad was running the electric carving knife in the next room.

If I experiment with different connections (interconnects, power cables, etc.) I can sometimes -- but not always -- make the sound come booming in, perfect, so there's no possibility at this point that what I'm hearing is speaker damage. The trouble is that the bad sound doesn't always go away when I do this little disconnection routine (I've tried every configuration, scientifically), and it always comes back, no matter what I've swapped.

One other symptom that might be interesting: when I get really lazy in my detective work and start connecting speakers to an already powered-up amp and preamp, I can hear a whisper of cloudy-sounding static, almost like the sound your ear would make if it was full of water. I know a person should never hook speakers to powered-up equipment, but in the past when I've done this incredibly stupid thing I haven't heard any such crackle.

It's not the source because it happens on different sources, and it's not any of the cables because I've switched them all out at least once. It's not RF pollution because I've treated the whole system extensively and, besides, it's in the wrong frequency band.

The mains in my house are NOT grounded, so at this point I'm thinking that it's a buildup of fault energy in the amp or preamp, but why would that affect the sound intermittently, and why only in this very peculiar, difficult-to-pin-down sort of way? Could a "bad cap" be the culprit? Any ideas are appreciated. I don't *think* I'm delusional, because non-audiophile friends can hear the difference, but on the other hand this problem has spanned several configurations of gear.
dog_or_man
dog_or_man OP
68 posts
 
Getting closer!

I just tried this exact sequence, and it worked:

1) I stopped the CD player but did not power off

2) I shut the preamp and power amp off (preamp into "standby")

3) I disconnected the speaker cables at the speakers

4) I disconnected the CD-player from A/C power, and re-established

5) I disconnected CD-player ic's at the CD-player end, and re-established

6) I powered on the preamp and the power amp (with no speaker connections)

7) I reconnected the speakers

I Pushed "play"... and everything was PERFECT.

....So what does everyone think, now?
twoleftears's avatar
twoleftears
5,318 posts
 
Hmmm. More technical-minded Audiogoners out there will be able to explain exactly why, but it can be dangerous both powering up your amp without speakers attached, and even more so connecting the speaker cables to your amp while it's powered up.

Your latest experiment is definitely interesting, but I'm not sure how much it narrows down the possibilities. IMHO, it demonstrates that:

(A) there is--as I think you suspect--some system synergy that is causing the crappy sound. Something like the build-up of a static charge or some such, which gets dissipated when you break connections and turn components off.

...or...

(B) there is--as I suggested before--some kind of partial or intermittent short, poor connection or something similar, in one of the cables or one of the components. As you suggested in a previous post, the mere act of connecting or disconnecting an IC to a RCA jack can change things, physically moving wires or solder joints and hence temporarily "curing" the problem. I once had an expensive pair of Acrotek 6 nines copper interconnect which if dressed in a certain way wouldn't pass any signal at all, and if dressed three inches in another direction worked just fine.

By the way, did you use your own original cables for this last experiment or the new ones?
dog_or_man OP
68 posts
 
I didn't get to keep the new ones, as my friend's system needs their extra length, but I'm relatively confident that I can rule-out cables as a potential cause because the problem recurs with the same frequency regardless of which set of my own cables I use.

A member of another forum suggested I clean all of the IC sockets with Caig Deoxit, which is at least cheap. Others seem to think we're getting closer to concluding that one or more of the connections between the various IC sockets and their associated circuit boards have been compromised.

I was totally convinced that the problem involved some sort of charge build-up and dissipation, as you have speculated, until I took the whole rig over to my buddy's house and it performed poorly straight out of the back seat of the car. Shouldn't a cold re-connection of the entire rig have started any charge build-up issues over from a base of zero?
twoleftears's avatar
twoleftears
5,318 posts
 
Does the same "bad sound" come equally from both speakers, i.e. are both channels equally affected? If so, I wonder if that discounts--at least to some extent--the interconnect theory (unlikely they'd both be bad). Beginning to wonder if it's some electronic component (e.g. capacitor) inside one of the pieces of equipment, that's just beginning to fail, and so is intermittent.

I keep coming back to the only scientific way of isolating the problem as swopping out, one piece or cable at a time, each and every part of the system, starting probably from the source component and working downstream.
dog_or_man OP
68 posts
 
Unless I'm way off (tell me if I am), it would seem that this most recent experiment at least isolates the problem at the CD-player, no? 'Cause I can take it out of the stack and run a crappy b-unit for a few days while someone local checks it over.
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