Yall know anything about the Vox AC30?

[ecc83]

It has been a common practice of mine, to pull the power tubes. Said earlier in the rack, so Marshall 100/100 mono blocks, mesa 50/50's..20/20's rack stuff.

Pardon me, you're saying that because it has a tube in the rectifier circuit I cant do that anymore?

It's just basic 'rithmetic friend. In cathode biased amp the EL84s need about -10V on their control grids to bias them to about 40mA which with say a 300V HT gives about 12W anode dissipation. Four valves going through a common cathode resistor is therefore 160mA and needs around 62Ohms for Rk* Now, if you pull two valves the anode current STILL needs to be 160mills to get ~10V so the poor pair left are now dissipating well over 20W EACH!

A fixed biased amp is different. The grid voltage is derived from the PSU and thus not dependent on anode current.

*These are ball park figures from out of an 80.5 yr old head. Actual values will depend on specific circuits and to some extent valve brand.

Oh! and BTW solid state or thermionic rectifier? make no difference in this matter. I hate valve rectifiers!

Dave.