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Help: Noisy Tubes

I have a Quicksilver Line Preamp with Sovtek 6DJ8 tubes. It sounded great for about 4 years when it started to sound quite thin. I replaced them with new ones from Quicksilver. Both tubes sounded great for a month then became very, very noisy (crackle, pop, etc). Quicksilver replaced one of them which also only sounded good for a month. Then I got some super-low-noise Sovtek 6DJ8s from RAM in Santa Barbara (they test and sort tubes). Same effect. Sounded great for 2 months, but now they are getting noisy too. AARGHHGHH! What the heck is going on?
srlivingston
4 responses Add your response
meisterkleef
146 posts
 
Sounds like it's time to send the unit for a check up. Could
be that some of the operating voltages are out-of-spec on
the high side (failed cap/resistor?) and prematurely blowing
out the tubes. Although I recently retubed my LS5mkII with
new Sovtek 6922s, the originals are still in perfect working
order after 7 years of fairly heavy use and are now serving
as my emergency back-up set. Preamp tubes should last quite
a long time if the unit isn't left powered-on 24/7.
marakanetz's avatar
marakanetz
5,473 posts
 
i also believe that problem is beyond tubes and you should check the rest of circuit for bad caps mainly.
stevenoda
3 posts
 
SR,

Specifically, have the bypass caps and cathode resistors checked. If the unit has had it's electrolytic main filters replaced---probably a good idea to replace those 'lytics on the gain stage and input tubes.
srlivingston OP
1 posts
 
Thanks for the advice. Sounds like it needs a tune up. Will send back to the manufacturer...

SL
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