#1
I own a hughes and kettner tube 50.
The previous owner of the amp changed the power amp tubes 3 years ago (no problem because he didn't play a lot) and he changed two of the original pre-amp tubes a month ago. But there is still 1 pre-amp tube that is the original one from like 15 years ago.
Now when I turn up the pre-amp volume on both channels it really sounds bad with lots of cracking sound and very bad palm-mute sounds.
It can't be the cab because I just played it with a few other amps and it sounds perfect, but when I tried the head on an other cab it still sounded the same (very bad).
So is this the one tube (so just replace it) or is there a larger problem here?

cheers
Hendrik
#4
No, I think you are right. It sounds like that one pre-amp tube went microphonic. I'd replace that before you do anything else. No need to bias a preamp tube.
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#5
Quote by tubetime86
No, I think you are right. It sounds like that one pre-amp tube went microphonic. I'd replace that before you do anything else. No need to bias a preamp tube.


What do I do if it still sounds bad afterwards?
I'll replace it tomorow, but if it still doesn't sound right what should I do?
I think if it would be a problem with the power amp tubes, it should normally lose power and sound weak. In this case it sounds fine till I put the pre-amp volume over 12 o' clock.
What other problems can an amp have if it's not the tubes?
I've seen the circuit for the clean channel and it's basicly the same as a fender blackface (with a gain tap for the B mode with more gain).
Could it be a circuit problem?
#7
if a new preamp tube doesnt work, focus on the power tubes, and if after that it still sounds bad, refer to an amp tech to look at your circuitry, transformers etc.

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#8
well, the cable isn't a problem as I tested out other heads with the same cable.
The power amp tubes still look good and would there just be about no volume comming out if there was something wrong with them, also the pre-amp tubes are the ones that really make the sound of the amp right? So should I put in a decent one? the two other ones are mesa's I think I'll just replace the one with a stock valve from the repair shop, they are about 15eu.