Running a 5u4gb in silverface super reverb

[Choan]

Hey guys, I have a mid 70s super reverb that has a 4ohm speaker load in the cab. I have another super that I’ve run a 5u4 in for years, no problem. I was wondering if running the higher current 5u4 in the amp with a mismatched load is dangerous for the PT. I put a spare 5u4 in and the plates read 406dcv, so there’s plenty of room to increase the plate voltage and lower the current with a GZ34.

[mresistor]

You could use a 5R4GB or GYB that has only 2A filament current and drops 50V.  Could also pull the first preamp tube (norm channel) to lessen total curren draw on the PT.


Running a 4 ohm load shouldn't be a problem.   I would have to ask why are you running a 4 ohm load? seems that 4 8 ohm speakers in parallel is 2 ohms. Which is stock config in an SR.


As for your particluar question concerning load mismatch and higer filament current draw by the rectifier being harmful to the PT.  I will defer to others.. 

[Choan]

Appreciate the feedback!

It’s a buddy of mines, he’s got a mix of 2 and 4 ohm speakers in there. The way it’s wired up read 4ohms on the meter. I’ll look into the 5r4 as an alternative.

[tubeswell]

I’ve run a 5u4 in for years, no problem.

All good then

[mresistor]

2 ohm speakers  ??   

[dogburn]

Appreciate the feedback!

It’s a buddy of mines, he’s got a mix of 2 and 4 ohm speakers in there. The way it’s wired up read 4ohms on the meter. I’ll look into the 5r4 as an alternative.

Is that reading measuring the actual impedance or DC resistance? If the latter, then the impedance is somewhat higher.