Currently Being ModeratedMar 9, 2012 12:08 PM (in response to Smart1960)Re: DT25HD/DT25112 speaker hum
Hum in Class A mode is totally normal- all the DT amps have some hum in that mode. It's just a function of the circuit design. But it sounds like you might have a problem with the DT head if the hum has increased. You might have a bad output tube EL84. Since you have two of the same amps, why not try taking the tubes out of the combo and put them into the head and see if the hum is less?
Chinese tubes are notoriously unreliable and tend to fail in the first hours of use. That may have happened to you. If there is a bad tube, it will be covered under warranty. Good luck!
Currently Being ModeratedNov 16, 2012 9:26 PM (in response to gtrman100)Re: DT25HD/DT25112 speaker hum
Hey Smart1960 did changing the tubes work?? I have the exact same issue. I just bought a DT25 head and cabinet (used). It is great condition and plays very nicely. I noticed the exact same hum in triode and worse in class a. It goes away in pentode - except for normal buzz/hum of a tube amp. The hum in triode is not normal or shouldn't be. How did you fix yours?? Changing the tubes and rebias work?? Thanks.