2. amps-preamps
  3. 1238695457

What does microphonic tube sound like?

I have this strange problem since I replaced my old SS preamp to a tubed preamp. Some of my CDs when played through Linn Unidisk sound scratchy. There is this annoying scratchy echoy sound throughout the CD and I can't listen to them. But the same CD, played through my PS1, sounds fine. I had both Linn and PS1 with the old SS preamp, and I didn't have this problem with that particular CD in either player.

I think the problem is with either the CD (bad press?) or the new tubed preamp. The current hypothesis is that the more extended sound from Linn is triggering preamp to misbehave and produce the scratchy sound, because the sound from PS1 is softer in extreme frequency ends. I don't know if what I'm hearing is microphonics, but if it is shouldn't it happen to all the recordings?
jylee

Showing 3 responses by shadorne

shadorne's avatar
shadorne
7,477 posts
 
I expect The Linndisk is overdriving the new preamp and this produces distortion - especially on a modern "loud" CD but less so on a CD made in the late 80's...

The PS1 may simply have lower output and therefore it does not overdrive your new pre.

Microphonics are a bigger problem with power amplification rather than the smaller tubes in preamps - of course it is always a drawback of tubes and it is best to place tubes away from a corner and preferably in another room if you listen loud.
shadorne's avatar
shadorne
7,477 posts
 
Mofimadness,

Good point. I stand corrected. The higher gain stages will make pre and pre-preamp microphonics more audible. However the bigger tubes are actually more susceptible to it.

Most people like the microphonic sound. In David Gilmour's studio they have put all their tubes in a completely separate room in order to avoid this issue.

However, I still think the OP might be overdriving the preamp, as the PS1 plays ok.
shadorne's avatar
shadorne
7,477 posts
 
If the CD player is indeed overdriving the preamp what would be the remedy short of getting a new CD player?

You simply need to attenuate the signal a little - a longer interconnect (12 foot or so) might do it as unfortunately your CD player output is probably fixed.

You could easily test to see if this is indeed the problem by placing the old SS preamp (which you claim works fine) between the CD player and your new tube preamp ....then vary the volume on your SS pre to see if you can reproduce the problem.
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