noise thru tube pre??


Is it normal that if I tap on the pre chassis that I can here it slightly in the speakers (like a record player picks up taps and such) just curious Chad
chadnliz

Showing 5 responses by newbee

You've got a microphonic tube. Since you only have one tube, get a new one thats been tested by a dealer for microphonics. Microphonics can effect the sound put out by your pre-amp even if you are not tapping the case. Vibrations come from many sources, including airborne.

Use currect production low noise tubes until you know the sound you prefer. Visit Audio Asylum tube forum and do a search on the 12AT7 you are using for suggestions on good currect production tubes. I don't use any in a line stage so I have no recommendations.

Re above comment 'microphonics can actually sound very good' - I would add 'if you like distortion'. In fact the presence of microphonics can give you some of that upper mid/high end distortion (glare, grit, grain, etc) that most folks hate.
Hell, I wouldn't even wink! SS sucks the music right out of the grooves and craps all over it! Hey, Nrchy, did you ever figure out how to bias that tube amp you bought? :-)
Fiddler, I think there is a difference between 2nd order distortion and a 'ringing' caused by tube microphonics overlaying the music.

That in minor amounts folks can enjoy an artificial reverb like distortion caused by this ringing I wouldn't deny. Studios regularily add re-verb to the mix to enhance a recording, especially dry studio recordings.

But, folks should know there is a difference and by having microphonic tubes you are allowing a distortion to exist which you have no control over. While some recordings might well sound better, and some systems might well sound better, the obverse is also true. And, if you are playing music or components that have considerable energy in the highs already, you might well find that the minor amount of microphonics added to the mix was enuf to make the sound unpleasant, but if you didn't know why you would blame the recording or your system.

Personally, I avoid microphonic tubes as I want the signal to hit the amp as clean as possible. I've always steered clear of any 'signal enhancers' because over the long haul I've always ended up taking them out of the system even though initially their effect was attractive. Thats strictly my choice. Others can tune their system as they wish.
Honest1, LOL. Just too much. I'm going to avoid temptation just this once. No comment!!
If you must put tube equipment in the same end of the room as the speakers usually you can put it in the center of the space between the speakers. Just put on some bass heavy music and move about finding the location where the bass response is minimal, usually well away from the back or side walls behind the speakers where the bass is reinforced by the boundries. If you are into TT's the same rational used for locating a turntable can be used for tube equipment.

FWIW, I've never thought that power tubes suffered very much, if at all, from the vibrations created by the speakers, but the small tubes are another issue. I have put large mono tube amps very near speakers (between the speakers) without any issues, but as indicated above I shy away from small tubes that aren't free of microphonics.