Rogue 88...high pitched whine

usp1 · « **on:** 18 Aug 2011, 11:17 pm »

A couple of days ago, I started hearing a very high pitched whine from my left channel. The whine persists if I change speakers. So I started switching equipment one at time and I have isolated the Rogue 88 as the source. I suspect this may be a failing tube since most of the tubes in there are of indeterminate age. Since the rogue has (2) 12au7, (1) 12ax7 and (2) KT88s per channel, I wanted to get some idea of which one is the likely culprit. Going through a process of elimination is going to be time consuming so I was hoping that someone with more knowledge can help me pinpoint the problem. Thanks for any help.

JakeJ · « **Reply #1 on:** 18 Aug 2011, 11:25 pm »

One thing you can try is tapping on the tubes one at a time with the amp on and the volume up just enough to hear the whine. This may excite it and help you track down the culprit. Other than tube rolling I don't know how to find it short of extensive testing with equipment most of us don't have, me included.

Ericus Rex · « **Reply #2 on:** 19 Aug 2011, 12:15 am »

Swap the tubes, one type at a time, from one channel to the other. When the whine moves to the other channel you'll know the tubes you just changed were the culprits. Start the with single 12AX7, then the pairs of 12AU7 then the pairs of KT88 (move these types as pairs only since they are likely matched and should stay that way). If the whine never does move to the other channel then something else is amiss. I think that amp is self-biasing. If it isn't, than rebias after each swap.

Ericus Rex · « **Reply #3 on:** 19 Aug 2011, 12:51 am »

You probably should mark the tubes with their current coresponding sockets before beginning the swapping.

JakeJ · « **Reply #4 on:** 19 Aug 2011, 01:40 am »

Duh!

Great idea, shoulda thought of it myself.

usp1 · « **Reply #5 on:** 19 Aug 2011, 02:11 am »

Thanks guys. I will try that. I was hoping there was something easier.

usp1 · « **Reply #6 on:** 20 Aug 2011, 08:15 pm »

I finally got around to this today morning. I swapped the left and right 12AX7 tubes and the whine went away from both channels. So i switched them back and again no whine. Not sure what was causing the whine before. In any case, the whine is gone and I am happy about it. I will deal with it if the whine comes back again. Thanks for all the help.

Ericus Rex · « **Reply #7 on:** 20 Aug 2011, 10:03 pm »

Sounds like the pins on those tubes got a bit corroded. Cleaning them will help. If the whine comes back with clean pins then I'd suspect a tube socket, or the socket/PCB solder joint.