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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: Tube preamp likes to sing with the music....HELP! (long). posted by Eli Duttman on February 23, 2002 at 13:36:38:
Dman,Do those 12AX7 or 5751 have aluminum shields over them? Sound like you've got some EM coupling going on with maybe a transformer or another tube, that is a bit too close to the problem child tube.
Try this goofy trick. Get a pice of corrugated cardboard. Wrap Aluminum foil over the surface. Connect the Mickey Mouse shield from the board to the chassis via a wire with alligator clips.
Now, turn on your unit. When the whistling starts, place that aluminum board between the culprit tube and anything that is near it which may produce an EM field.
See if that changes the volume and pitch of the noise.
If your tube HAS covers, the orientation of the cathode caps and resistors may induce coupling. Simply rotate one cap or resistor 90-degrees and see if that helps.
In this low voltage gain stage circuits EM can be a big pain in the rear. Due to the sensitivity of the stage and the amount of gain.
Good luck. Hope it works---Hey, at least it's cheap.
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Follow Ups
- EMF coupling - steven oda 13:58:07 02/23/02 (0)
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