TheEvan Posted August 4, 2009 Share Posted August 4, 2009 I've had this affliction before on different equipment. I assume it's one of my amp tubes since I changed my preamp tubes.. It's a high-pitched noise, fairly constant, of low amplitude. It's hard to guess its frequency, but it sounds somewhere up toward the limits of hearing. Quote Link to comment Share on other sites More sharing options...
Coytee Posted August 4, 2009 Share Posted August 4, 2009 Can you swap channels to see if the sound follows a amp? Then...could you swap tubes between each amp? (presuming monoblocks) otherwise, swap between channels?? That might help narrow it down Quote Link to comment Share on other sites More sharing options...
LarryC Posted August 4, 2009 Share Posted August 4, 2009 Does it come directly from a tube or through the speaks or both? Does tapping the tubes one by one bring it up or get rid of it? You might be able to localize it that way and change that tube. Quote Link to comment Share on other sites More sharing options...
Moderators dtel Posted August 5, 2009 Moderators Share Posted August 5, 2009 It's the sound of that little wheel spinning on your electric meter from that amp and ac trying to keep up. [] Or the sound of a needle grinding thru vinyl . Sorry TheEvan just kidding couldn't help it, ok that's enough of being an jack@ss for one thread [] Quote Link to comment Share on other sites More sharing options...
mark1101 Posted August 5, 2009 Share Posted August 5, 2009 Do you have a TV with a CRT nearby that is on? If so, try turning it off. It could be the Horizontal Sync which operates around 15Khz. I have that problem but have gotten used to it. I can barely hear it at all anyhow unless the room is dead quiet and I am right up near the TV. My kids tell me they hear it all the time, and so I pulled out my RTA setup and Mic.....and sure enough, that's how I figured out what it was. If you have an RTA setup and mic you can find the souce and frequency in seconds. Quote Link to comment Share on other sites More sharing options...
jacksonbart Posted August 5, 2009 Share Posted August 5, 2009 You know it may not be the amp. I kept hearing a noise in what I thought was comming from my system and after a few hours fussing with things to no avail, I simply walked around the room and found this guy. He was making an awful racket and frankly also gave off quite an oder. Apparenly my wife had left the door to the jungle room open. All is better now. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted August 5, 2009 Share Posted August 5, 2009 If you can isolate the noise to an amp, it is likely that the amp is oscillating. Using a 'scope or a signal tracer, work through the amp circuitry until the problem can be pinpointed, then replace the bad component. I am assuming that the noise is coming through the speakers. If the noise comes directly from the amp, loose transformer laminations are sometimes the culprit. Quote Link to comment Share on other sites More sharing options...
tromprof Posted August 5, 2009 Share Posted August 5, 2009 I had a pair of EH EL-34s that would emit a high frequency pitch, esp. before being warmed up well (30 min. or so). They would also make a lot of noise after I shut down the amp, it sounded like they were trying to crack. I cured it by replacing them and discovereed that they didn't sound very good either. Try tube swapping and see if that helps. Good luck! Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted August 5, 2009 Share Posted August 5, 2009 Thanks for sharing JB. Has the little guy started kindergarden yet?[6][<)] Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted August 5, 2009 Moderators Share Posted August 5, 2009 Are any of your tubes 6dj8 by chance? Travis Quote Link to comment Share on other sites More sharing options...
TheEvan Posted August 6, 2009 Author Share Posted August 6, 2009 No 6dj8, dwilayer, but I do have EH EL34's as mentioned by the 'tomprof' (at the Cincy Conservatory perhaps?). I set up for a big 'ol troubleshooting session. Hah! I played for hours and could not raise nary a noise other than the obligatory faint tube rush. I'll have to sneak up on it quietly next time so it doesn't hear me coming... Quote Link to comment Share on other sites More sharing options...
thebes Posted August 6, 2009 Share Posted August 6, 2009 Do you have track lighting, neon lighting or anything on a rheostat? I often have a noise that sounds like what you are describing but it's caused by my dimmer, yet seems like it's coming from the amp. Quote Link to comment Share on other sites More sharing options...
TheEvan Posted August 6, 2009 Author Share Posted August 6, 2009 Not that, thebes. This is almost a ring and at a much higher frequency. Besides, it's intermittent. And I turned off all such offenders when it happened previously, to no effect. Hey, now that I brought this up may it'll never happen again. THANKS, GUYS. Quote Link to comment Share on other sites More sharing options...
LarryC Posted August 7, 2009 Share Posted August 7, 2009 Did you lightly thump each tube in turn to see if it starts or stops? Best done while it's ringing IMO. Quote Link to comment Share on other sites More sharing options...
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