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noisy tube preamp

I'm fairly new to tubes but have recently acquired a tube preamp. I'm really liking the air and the soundstage it provides, something the solid state stuff haven't done as well but the one issue I have is the elevated noise floor. It's really only audible when no signal from the source is being played, like when the system is simply on or when the song stops. Also there is an occasional quiet, short lived buzz from the speakers that pretty much goes away after the preamp warms up and lastly, after the unit has been on for several hours, like 24+ it will start to emit a high frequency pitch that also is only audible with no music playing but it is louder than the inherent noise floor of the pre. My question is, is this something I can remedy by rolling tubes or is it something that has to do with the pre itself like the design or a failing part? Btw, it's a jolida fusion preamp.
lukaszwk
newbee
4,822 posts
 
Could be as simple as needing some very low noise tubes. Could also be too much gain for your amp/speakers and the 'noise' issues could be solved by using a fixed in-line attenuator. But that turn on 'buzz' and high frequency noise after 24 hours, I don't know. But then I would never leave a tube unit on for 24 hours......The turn on buzz is probably nothing more than the unit stabilizing, something many pre-amps avoid by having a mute circuit which engages on turn on (for up to several minutes).

Tackling the tubes first is a good place to start. Sooner or later you will have to change them out, so even if this is not 'the' problem having the spare set is a good idea anyway. 
hifiman5's avatar
hifiman5
1,836 posts
 
The high frequency whine that you mentioned rings true to me.  I had the same experience and found the problem to be with the tubes, not the preamp.  Not sure what tubes you are using but I have had great luck with Cryoset.  They cryogenically treat all of their tubes which, in my experience, has resulted in very quiet tubes that seem to last forever.  I buy new production Gold Lions and they have been great.

Good luck!
atmasphere's avatar
atmasphere
12,177 posts
 
after the unit has been on for several hours, like 24+ it will start to emit a high frequency pitch that also is only audible with no music playing but it is louder than the inherent noise floor of the pre.
That is a form of something called 'microphonics' and is a property of all active devices. Tubes have it more than solid state, and its definitely something that you can get rid of by changing a tube!
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