2. amps-preamps
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Hum in VTL 125 mono block amps

I have VTL 125 mono block amps they are about 11 years old with fresh tubes as of late they produce a hum or buzz in the speakers that they never had . Nothing in the system has changed , I get the hum- buzz even with the pre amp muted the level of buzz- hum does not change even when I un mute the pre so I think the hum -buzz is from the power amps. All eq is on a dedicated 20 Amp line cables are top of the line Ridge Street Audio power cables and Ridge Street poiema 3 IC'S / speaker cables. Do any of you have a idea what to ck is a cap starting to leak due to age or something else. Marc
lake513
lake513 OP
123 posts
 
I have now tried 4 different set's of tubes - Brimar , Telefunken , Mullard and Ram all 12AT7's no difference in the hum -noise level. I am at a loss as to why a hum- buzz has started happening as I never had it before and nothing else has changed in the system. I do not have a new set of output tubes but have several sets of lightly used EL34's and will try that and see if that makes a difference right now I use KT77's and I really like the sound from them they are JJ KT77's .
katylied
54 posts
 
Try also to check if the hum comes from a bad connection in the IC. The best way to know if the culprit is the amp itself is to short the input (a cheap RCA with a link between the hot and cold connection) and also try one amp at time.
mrtennis
3,295 posts
 
is it possible that you can try a different amp ?

although probably a waste of time, you could change the power cords and or use cheater plugs.
lake513 OP
123 posts
 
Katylied ; Good idea , I have tried one amp at a time still the hum I will try a different cable later today. Mrtennis ; Thanks for the idea I will try both things later today a different amp not possible right now but may be able to try that later Thanks Marc
newbee
4,768 posts
 
Couple of other things to try...

1) Disconnect the amp from the pre-amp, muting may not be enuf.
2) Makes sure that all unused PC's are disconnected from outlets (believe it or not another hum I had was sorced to exactly that!).
3) If that fails, bite the bullet and disconnect and unplug everything and start from scratch. One amp to one speaker, then the other, then both together, then add back....Sooner or later you will hear the hum and you will know the source.

Hope that helps a bit.
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