2. amps-preamps
  3. 1221700245

Tube preamp noise

I acquired an all tube preamp, and one thing I immediately noticed was that the preamp is super sensitive to any external impact, however small may it be. With a gentle tap on the cover of the preamp is echoed and heard on the speaker even when the volume is set to minimum. Same thing when I tap on the audio rack, other equipments (power amp, cdp, turntable), and even on the floor.
It is just like the sound you would hear from the PA speaker when you tap on a microphone.
Is it common on certain preamps?
Anybody experienced this?
128x128ihcho
jafox
1,466 posts
 
Furthermore, among 4 sockets, one socket always generates more tapping noise regardless whatever combination of tubes used.
This might also indicate that a tube socket needs to be replaced.
ihcho's avatar
ihcho OP
612 posts
 
Socket replacement? It is an easy job?
How often a socket can go bad? Is it a common problem for tube amp/preamp?

Thanks much for your help.
ihcho's avatar
ihcho OP
612 posts
 
"You might buy some new production 6SN7 tubes...like Shuguang...and install those. The new tubes should not be microphonic, especially if they are purchased from a dealer that screens for this problem."

I got Shuguang 6SN7, and yes, I found they do not suffer from the microphonic problem. From new fresh out of the box, they do not sound as good as Sylavania or GE, but at least I am glad to find out the problem wss due to old/bad tubes, not to the sockets or other parts of the preamp.
Thanks!
Post removed 
dgarretson
2,601 posts
 
I don't think I've ever had a 6SN7 (or many other types) that are not microphonic to one degree or another. Unless the problem is severe it doesn't indicate that the tube is not performing well in other respects or that the tube will fail prematurely. Minimize it with tube dampers & decouple the component from the rack. If slightly microphonic NOS tubes sound better than Chinese, then use them!
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