RAPTORMAN Posted March 14, 2005 Share Posted March 14, 2005 I was listening to some records and all of a sudden I hear this whooing sound coming from the left Khorn. I stop the turntable right away and put the preamp on mute--the sound was still there. It was a weird sound almost like an echo. After a few seconds it went away. I notice when I tap on my CAT SL1 preamp the tapping sound is coming right out of the left speaker. When I turn off the amp or put on standby the tapping sound is not there anymore when I tap on the preamp. The sound is only on the left Channel. What is going on here?/HELP..HELP..HELP.. Quote Link to comment Share on other sites More sharing options...
cwm Posted March 14, 2005 Share Posted March 14, 2005 Sounds to me like a "microphonic" tube, i.e. the tapping causes the loose tube element to move or vibrate....try changing them out. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 14, 2005 Share Posted March 14, 2005 Start with the preamp and switch tubes channel to channel and see if it follows a particular tube. If nothing shows itself as the culprit there you can repeat it on the amp or better yet just run the amp with a preamp off if the channel is quiet with the preamp off that pretty much rules anything on the amp being the source of your noise. Craig Quote Link to comment Share on other sites More sharing options...
RAPTORMAN Posted March 14, 2005 Author Share Posted March 14, 2005 Craig Rjp Thanks. Found the problem. 12AU7 tube on the line stage. Replace them and everything seems to be OK. Just don't understand why line stage; I was playing the TT. Quote Link to comment Share on other sites More sharing options...
WMcD Posted March 14, 2005 Share Posted March 14, 2005 In any amp I've seen, the phono stage is just an additional pre amp, plus equalization, before the line stage. So you're always listening to the line stage too. It has been some time since I've had an amp problem or played with them. However, one problem is called "motor boating" which is, naturally, a low frequency oscillation. My guess is that the oscillation and microphonics may have a common cause - - something going wrong with the tube. The real experts can tell us more. Gil Quote Link to comment Share on other sites More sharing options...
Deang Posted March 14, 2005 Share Posted March 14, 2005 "The real experts can tell us more." LOL. I always thought of you as a "real expert". If you can't explain it, then we'll have to go with my advice: Don't tap on it and maybe it will go away. Quote Link to comment Share on other sites More sharing options...
Klewless Posted March 15, 2005 Share Posted March 15, 2005 You could just unplug it and the racket will never return! Quote Link to comment Share on other sites More sharing options...
fini Posted March 15, 2005 Share Posted March 15, 2005 I used to be bothered by an echo every time I played my "Snow White" DVD. I just decided to leave well enough alone. Quote Link to comment Share on other sites More sharing options...
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