EL34 Tubes in Mark V (Groove Tubes GT-E34LS)

I just purchased some Groove Tubes GT-E34LS to swap out my existing 6L6 tubes in my Mark V.

I am questioning if these were the right tubes for the Mark V.

I bought 2 matched pairs (inner and outer tubes).

Upon turning on the amp I can hear a high end squeal on Channel 3 and low end oscillation on Channel 1.



Regards

RK

I wouldn’t run EL34Ls in a Mark V. They run hotter than regular ELs and may cause over current. If you still want to run them make sure you are in variac mode. The squeal is likely a bad tube.

Also, did you make sure to set the Bias switch?

Yes I am in Variac mode and the bias is set to EL34.

When I was changing the tubes out I turned the head upside down so that I could push the tubes into the preamp (instead of having it right side up and pushing the tubes upwards). I then turned the head on while upside down. I head what sounded like a mechanical click noise coming from the fan. I turned the unit off and then turned it back right side up. The click continued for a bit and then stopped.

I still have some high pitched squeals, and heard what sounded like a chopper sound (not clicking) which goes away when my hand touches the strings of the instrument. If this were a tube issue I assume it would be a preamp tube. Could I have blown one of these when the head was upside down and/or while switching out the 6L6 tubes?

Thanks

Took the Groove Tubes back to my guitar store and they noted that I should really be using Mesa Boogie EL34s. I swapped them out and everything sounds great now. I would not have expected this - but problem solved!

Thanks

I had similar issues with my tubes, mostly preamp. I used deoxit spray to clean the tube pins and sockets and that cleared up any odd noises. Hopefully you don't have bad tubes. Did you use deoxit to clean the sockets? I do this almost every tube change.

You must use Mesa tubes? That's a joke, not true at all. That's what a guitar store says. I would challenge them on that for sure. Lots of clowns work at guitar stores.

You can use what you like. I have used Mesa amps since 1999 and never used Mesa tubes and never had noise issues. All they are are rebranded tubes anyway. Any good tech will tell you, use what tubes you like, but always clean the pins when installing new tubes. I have gotten so many odd noises without cleaning the pins/sockets. I never use Mesa tubes, don't like their choices. My Mark V is dead quiet. Most silent amp I have owned and the first thing I did was pull the Ruby tubes or Mesas.