2 chan dual rec tube issue?

[filteredsoul]

I've had a mid 90's dual rec for a long time and currently it has a "Dougs Tubes" cocktail of tubes in it. His preamp mix and 4 matched ruby power tubes. I use the silicon diodes for the rectifier section... The tubes are about 4 years old and the amp has started making a hissing, swirling sound when the amp is on. Switching to standby makes it go away, but turning it back on is kinda random. Sometimes the hiss is there, sometimes not. I primarily play the clean channel with just a touch of gain so the hissy swirl sound isn't from a high gain setting.

Well, I was playing this morning and the amp sounded like it had "half power." I don't know any other way to describe it. But as I played, it would smoothly go from the full sound I expect, to a half power choke then back again. -Kinda hard to have any confidence when it's doing that. The longer I played, it seemed to get better, but no matter what I switched, it was there... both channels, bold-spongy power, etc.

I'm figuring this is a preamp tube issue. Any other ideas? I have no other tubes to try so I'll be contacting Doug in the morning unless there's an obvious cure that I'm not aware of. I'm doing a live recording this coming weekend so I need this thing fixed.

Thanks for the help and/or ideas!

Dan

 

[fishyfishfish]

Tubes are culprits.

 

[mikey383]

Your power tubes need replaced.

 

[filteredsoul]

Power tubes?
Isn't it more of a preamp tube issue?

 

[R_ADKINS80]

More often than not, volume fluctuations are a power tube issue.

 

[clutch71]

Tubes can sometimes just go bad.Even new ones. One of the drawbacks to using tubes. If they haven't been in there long, contact Doug and explain the problem. I had a bad 12ax7 and sent it back to him. He sent me a replacement in a matter of days.