Bottlehead Forum

Bottlehead Kits => Kaiju Stereo 300B amp => Topic started by: Deke609 on August 05, 2020, 09:59:50 AM

Title: Ideal plate-to-0V voltage for Kaiju 300B?
Post by: Deke609 on August 05, 2020, 09:59:50 AM

The schematic shows B+ of 450 VDC. The manual tests call for 490 VDC +/- 20%.  Both figures are for B+ before the plate choke and do not take into account the voltage dropped across the DCR of the choke.

Since I am rebuilding my Kaiju, I can dial in the plate-to-ground voltage. What voltage at the plate (relative to 0V) should I aim for to hit PJ's intended operating point?

MTIA, Derek

Title: Re: Ideal plate-to-0V voltage for Kaiju 300B?
Post by: Paul Birkeland on August 05, 2020, 07:36:18 PM

The target is approximately 370V plate to cathode and 70mA.  If you're off a little bit it isn't the end of the world.

Title: Re: Ideal plate-to-0V voltage for Kaiju 300B?
Post by: Deke609 on August 05, 2020, 08:47:11 PM

Many thanks PB. So @ 70mA plate current, that makes bias -70V, so 440V plate to 0V. If the target B+ before the plate choke is approx. 450V, then about 10V is dropped by the choke.  So a DCR of 140R, give or take. My 53H/80mA chokes have a DCR of 160R, so very close -- a measly 1.4V or so extra drop.  And the new OPT's have 3K3 primary impedance, also pretty close.  So maybe I won't need to do much and can just shoot for 450V out of the new HV reg. 

cheers and thanks, Derek