Toob Trouble

[charley95]

I just set up my Rogue Cronus Mag. last week and played all week. I just rolled my first set of tubes today with RCA clear tops NOS 12au7's and 2 new Gold Lion 12ax7's. Upon letting it warm up before playing I noticed a faint hum in the right channel speaker. It finally went away and played music most of the afternoon with no trouble. Upon stopping the CDP the hum came back a bit louder in the right channel. I'm assuming I have a bad tube somewhere but not sure which one or how to tell. The three clear tops appear to be glowing just fine with no red plating. I'm unable to tell if the ax7's are glowing or not. This is my first experience rolling tubes and I'm not happy!

Any help would be greatly appreciated.

[dragon1952]

Replace each tube, one at a time with an original tube until you find the culprit. You can't really tell by the glow.

[charley95]

Thanks! I'll try that today and call Rogue to try and narrow down which tube it may be. I would assume it's a right hand specific tube?

[heiney9]

Sometimes removing the tubes and re-seating them and/or cleaning the PINS will eliminate the problem. Tubes can be finicky at times, it's the nature of the beast. Be patient and try to do the simple things first.

H9

[heiney9]

Also if you are this ticked off already, then perhaps the tube the path isn't right for you. Tubes are finicky and they have weird issues sometimes. 98% of my issues with tubes as far as noise is solved by cleaning the pins and/or re-inserting the tubes. You do get a bad tube once in awhile, but of all the used NOS tubes I've bought think in the several hundreds I've had only one completely fail and only a handful (maybe 4 or so) that made permanent noise, meaning they were at or nearing the end of their useful life.

H9

[charley95]

Not so much ticked off as disappointed! I love my amp and this is minor compared to real life problems that we all face. I will try cleaning the pins today and reset them. Thanks for your input! I'm sure that this will be easy to resolve.

[heiney9]

Yeah, I know, maybe "ticked off" was a poor word choice. I will say I haven't experience hum from a dirty or poorly seated tube, but with tubes even the most minor thing can sometimes cause a noise issue. Even then it doesn't happen very often.

If doing that doesn't fix the problem, then you will have to start trouble shooting and narrowing down which tube or part of the amp the noise is coming from.

H9

[Joe08867]

My guess is one of the 12AX7's is humming. Happened to me a couple of times with NOS 12ax7's. Clean them and carefully and seat them slowly. Make sure they look very level.

If you clean or replace them and it still hums look around the room. Do you have a fluorescent or halogen light near the amp? I had hum from a lamp drive me crazy for a couple of days. It was one of those desktop halogen lamps.
I had a buddy that had a noise from his caused by his cordless phone base that was very close to his amp.

It is amazing what can cause hum with Tube stuff, especially older tube stuff. The RCA's could just be sensitive to RF.

[cstmar01]

I had a tube making a high pitched harmonic ringing sound when I wasn't playing music. I went and reseated the tubes and found that it took care of the issue.

I was in the same boat as you with not understanding how to tell which tube. I have 8 6550C's per channel so it can be a bit to work thru but they sound just soo good. IMO its worth the time to go thru them.

[organ]

Like others have mentioned, it could be dirty pins on the tubes.
My experience with NOS tubes is that, even with clean pins, *some* are just noisier than current production. I find current production tubes are quieter in most modern tube gear.
Hope you find the problem soon.

[charley95]

Turned out to be the center pre amp tube. Spoke with Mark at Rogue and he guided me on what to do. I put the original pre amp tube back in and the hum went away. I had an extra clear top and letting it warm up now. It's nice to be able to speak with the horses mouth when you have questions on their product.

[charley95]

Problem solved!

Thanks for your help!

[doctor r]

Excellent. As previously said tubes can takes us to great heights and can make us severely disappointed and depressed. We struggle through the disappointments in order to achieve that improvement we are always looking for. Join us as we all fall down the rabbit hole. Glad the hum is gone.