2. amps-preamps
  3. 1054275268

Weird ring/thump noise when I hit my speaker cable

Help please! I noticed a weird problem which I can't explain for. I hope somebody can tell me what's wrong. When I use my finger to flick at my left speaker cable, my left speaker will produce a short ring/thump sound in time with my flicks.

When I switch off my amp (Unison Research Unico), the problem will immediately disappear, and won't re-emerge immediately after I switch on the amp again. I haven't noticed a pattern of when the problem emerges - sometimes it's there and sometimes it's not.

The sound is also produced when I use my knuckles to knock my hi-fi rack (although not quite as loud as when I hit the speaker cable directly).

I have only noticed this problem when I recently bought the Unico and not before with my old Roksan Kandy. I was wondering whether it's due to one of the tubes having some loose parts that react to the jolts. But then the problem should be there all the time and not only some of the time.
lohkkw51e5
marakanetz's avatar
marakanetz
5,473 posts
 
Karls, tube microphony issues were resolved in late 40's. Now if tube has a microphony its a bad tube or will blow soon.
karls
332 posts
 
Marakanetz, have you ever actually TRIED IT? Not just on one particular tube, but on many different ones? I'm not claiming that they all ring like a bell, only that they do in fact have SOME microphony and that it varies a lot depending on the type of tube. As you would expect, it is usually most obvious in high-gain small-signal applications (phono stages, preamps, input tubes) rather than big output tubes. And if this issue has been fully resolved, why in the world would anyone want tube dampers or fancy platforms to set their tube preamps on? It would appear that you have unwittingly already taken my advice to heart:)
marakanetz's avatar
marakanetz
5,473 posts
 
Karls,
I used to manipulate with different tube applications including powerfull radio transmitters and had these tubes in my stock hundreds and never thought how much they could cost... Pennies at least 15...20 years ago for small signals and $1...2 for the output power ones. Even if a tube had a slight reaction on tapping or knocking on chasis it was considered a bad tube even if it was brand new. What simply was done with that tube is disposal and replacement with no remorse whatsoever and it's equally valid for all not only input or phono but the output tubes as well.
As per russian tubes he..he...(that's where I'm from) it's a normal thing to have out of 10 5...6 normal so don't tell that tube microphony is a normal thing for any of the application... it's wrong man.
sean
6,229 posts
 
I agree with Marakanetz. Any tube that is microphonic should be pitched or at the very least, not used in an audio system. Sean
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