2. amps-preamps
  3. 1321182764

Slight Tube 'Whistle' - Help?

Hi. Two Questions on my preamp:

1. Someone asked me if the pre is "hard on tubes"...what does this mean?

The EH stock tubes became super-hissy after 800 hours...stock replacements on the way. Meanwhile, i put in Amperex 6922 US PQ White labels...better in every way. Silent...until just recently. After about 300 hours with the Amperexes, i now [occassionally] hear the teeniest, tiniest bit of "whistle" thru the R tweeter only. In general, the hiss is super, super quiet (and i have 95 db speakers)...but [sometimes not always] it has gone from effectively silent to a soft whisper now in both channels.

Can a preamp be 'hard on tubes'...and if so, is there anything one can do? Or is the 'teeny R-channel whistle' a symptom of this or something else...or just par for the course with any preamp...particularly one with a ridiculously low noise floor? i cannot get over how much super-soft detailing i can now hear thru ordinary recordings.

2. In trying to figure this out, with the unit on, i tapped each tube out of curiosity...and discovered i could loudly hear it thru each speaker. Is this normal? Should i care since i dont tap my tubes while i listen?

Other than the teeniest, tiniest bit of hiss and this occassional 'whistle', the unit is dead silent...so perhaps this 'tapping' business is a non-issue?? The tube sockets themselves are on their own floating suspension systems underneath in the unit apparently.

If i put an EAT tube damper on each tube, should this stop it? Again, should i care?...is this normal?

Thanks for any guidance!!!!!!!!!
lloydelee21

Showing 1 response by mlsstl

mlsstl
1,462 posts
 
Yes, a circuit can be "hard on tubes" by running them toward the upper end of their designed voltage limits. Or, an off-kilter component elsewhere in the circuit can stress tubes. (I had a CJ tube preamp a few years back that developed a whistle when a power supply capacitor began failing.)

You didn't give the make/model of your preamp, but it might be worth calling the manufacturer and discussing the situation with them. You might want to have it checked.

And it is also not uncommon for tubes to be "microphonic" - some tube types are more sensitive than others. A tube damper can help if you think it is affecting the sound quality of your system.
More to discover