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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
lloydelee21 OP
1,202 posts
 
Thanks, Atmasphere. i always enjoy learning from your posts. I took the tube out, tapped it lightly on the pins and re-seated the tube. It has been as quiet as in the beginning ever since.

A recommendation from Brent Jessee who has been great as long as i've done business with him.
atmasphere's avatar
atmasphere
11,844 posts
 
Yes, some tubes seem to respond well to getting knocked about :)

I remember a few years ago we got in a batch of JJ 12AX7s for a guitar amp we make. They were all microphonic and unusable until they got thumped against a counter top. That seemed to sort them out...

I would regard something like that as a temporary solution, although in the case of those JJs, it seemed to be permanent!
lloydelee21 OP
1,202 posts
 
Thank you for that...good advice as usual!

BTW, sometimes, when i have just turned on the entire system in the morning, it sounds like a vacuum cleaner is coming thru the speakers for about 5 seconds, and then it is perfectly quiet the rest of the day. If i mute preamp, during the 5 seconds, it is gone...so either tube DAC or preamp. But what specifically might that be?
lloydelee21 OP
1,202 posts
 
oh...and the vacuum cleaner noise thru both speakers is almost as loud as a vacuum cleaner and does increase/decrease with volume control during the 5 seconds.

i will switch sources next time it happens to see if it is the tube DAC or the pre...but thought i would ask. AGain, after 5 seconds...dead silent the rest of the day. it is getting onto winter and it can be a bit cold in the room in the early am. thanks for any advice.
atmasphere's avatar
atmasphere
11,844 posts
 
That sounds like a warm-up issue that can be associated with a tube or a regulator. It is not an indication of failure, more its sort of a curiosity.
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