Studio 22 with only one output tube?

[tonejam]

Greetings everyone. According to Kevin O'Connor of LONDON POWER amps, you can safely use a Studio 22 (or any other fixed bias amp) with only one output tube. He says it is then operating in class A. I've tried this, and it works, although I must say I haven't noticed much difference in tone or volume level (at a VERY small gig). Would like to read some of your comments. Cheers, Bill.

 

[MesaDCLP]

Studio 22 is class A, even with 4 el84s.

 

[tonejam]

The studio 22 has 2 el84s, running in class A/B, I believe

 

[Gruffnutz]

I wouldn't trust that looney with my Valve Junior, let alone my Mesa. He won't replace your OT when it all goes pear shaped...

 

[stokes]

That amp has a push-pull output.Pulling one tube causes the output to amplify only one side of the signal.Has nothing to do with class A or A/B.If you crank the amp with only one tube,it will sound like crap.You are only using either the top or bottom portion of the "sine wave" coming out of the PI tube,as well as only using one side of the OT.It may not hurt the amp,but it cant possibly sound good except at very low volume.It doesnt make your amp operate in "class A",what it does do is make your amp "single-ended" to some degree.Pulling one tube may alter the voltage and bias point on the plate to some degree,unless you check to make sure the volts/bias are still "safe" I wouldnt do it.

 

[tonejam]

thanks for your input, I appreciate it.
Anybody out there had dealings with London Power? They have a large number of mod kits available, and I wonder if they're worthwhile?
tonejam.