Grandmeister 40 Deluxe Hum

Well I got this beast and changed the tubes putting new JJ’s in it. Worked great for a few weeks and sadly I haven’t used it all that much. I now have a very audible hum in general. It doesn’t matter what preset or even if a guitar or cord is plugged in. What would be a great sound is overridden by the rather loud hum. I did change the speaker cables to a heavy “Pro grade” cable and I have yet to swap them out as I have been busy working a lot of overtime. I’ll let you guys know if the cables are at fault. If not, anyone have any suggestions? Bad tube possibly?

Speedriff wrote:Well I got this beast and changed the tubes putting new JJ’s in it. Worked great for a few weeks and sadly I haven’t used it all that much. I now have a very audible hum in general. It doesn’t matter what preset or even if a guitar or cord is plugged in. What would be a great sound is overridden by the rather loud hum. I did change the speaker cables to a heavy “Pro grade” cable and I have yet to swap them out as I have been busy working a lot of overtime. I’ll let you guys know if the cables are at fault. If not, anyone have any suggestions? Bad tube possibly?

Sorry to hear this. My Deluxe 40 has more hum than I would like. I first swapped out pre-amp tubes in case that was the issue, helped a bit but not entirely.

When my amp was making weird humming sounds. At the time I posted some video to a music FB group and had multiple replies from techs in my city. While I think I solved that particular issue with replacing one of the preamp tubes, I had some interesting replies (and the amp is still noisier than I would like)

One amp tech replied:
" Apart from a possible tube issue which should be tried first before anything else. It can also be the main Mosfets bad or going bad. Around there would also be considerable to be the filter caps and plate resistors. [SIC]  I work at a repair shop and I'm an amp tech here and we've had a fair share of these amps in here"

A second commenter (not sure if they are amp tech) wrote:
" Sounds a bit like mains hum, but would think it would be more consistent. Do you experience this in other locations the amp is plugged in? My house is poorly grounded, and causes amps to make low rumbling sounds, especially when boosted or on drive channels. Just troubleshooting before saying dig into the amp. Might try another location, just to see, but clean channel definitely shouldn't be real noticeable. Definitely gotta keep digging. Real disappointed that I keep seeing issues with tubemeisters. They look and sound great, but I've seen quite a few different issues."

Finally, a third wrote:
" The self biasing circuit has some mosfet transistors on the cathodes of the output tubes. This is how the biasing circuit regulates the current of each tube. I worked on a Grandmeister 36 just recently with the exact same symptoms and one of those mosfets was partially shorted. They are Q14, Q15, Q23 & Q24. It’s “cycling” because the self biasing circuit is trying to regulate the current on the tube with the shorted mosfet... but can’t. But as you’ve noticed, it sure keeps trying!
Getting the circuit board out of that thing to change one of those mosfets is a PITA. I can take care of the repair for you, just PM me."

I know this may not be exactly the same constant hum you are experiencing, but maybe this info can help you or your amp tech!

I am still trying to decide if I try and better figure out my Deluxe 40. Live with it being noisier than I like (for functionality's sake...the ipad app is awesome to be able to sit away from amp head!) I already upgraded the tubes so I don't think that is the issue. Doesn't help that I have a small amount of ground hum that I can't eliminate (tried all sorts of trouble shooting, power conditioner, Hum-X, etc, no luck). The Deluxe 40 seems to really bring out some of that noise, especially if I add any gain it is really static background noise. I just bought a Quilter Mach2 to test out as a 'solid state' alternative, and see if my issues are with TM40 / tubes / or power. it arrived yesterday...needs a little more dialing in to get it apples-to-apples though. People either seem to love it or not care for it.  At the end I will sell one of them (or both, and keep on this quest for usable quality tone!)

Hi and thanks for the reply. I troubleshot the amp and turns out the new JJ tube in the V1 spot was bad. They sent out a replacement and all is well. Great customer service all around.