## Power section calculator

Cowasaki
Posts: 33
Joined: Wed Feb 24, 2021 5:27 pm
Location: UK
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### Power section calculator

Does anyone know where there is a power section calculator?

I am building an AB763 amplifier (close to the Vibroverb so https://robrobinette.com/AB763_Model_Di ... #Vibroverb) but with 1 additional 12ax7. I am using a GZ34 and 2x 6L6GC tubes

So I have a 290-0-290v HT @ 210mA, 6.3V @ 6a & 5v @ 3a

So the filaments come to 4.2 amps approx, the HT comes to 185mA

Now my initial setup is:

B+ at standby switch = 375v
B+ after choke = 374v

B+2 = 372v (B+2 powers the 2x 6L6GC

dropping resistor from B+2 to B+3 = 1K @ 3W

B+3 = 360v (B+3 powers the 12AT7 phase inverter)

dropping resistor from B+3 to B+4 = 4.7K @ 3W

B+4 = 325v (B+4 powers 2x7025, 3x12ax7 & 1x12at7)

I think the B+3 & B+4 voltages are too high. A calculator would be helpful if anyone knows where there is one. It would just assist in changing a few values to see what works. I think the 1K needs to be increased. My normal thing would just be to try increasing that but something a bit more logical would be great.

EDIT 4th Jan 22: I was running the amp at max cold whilst making adjustments and testing. Just biased it to 22W per tube and the B+2 is now 355v and B+4 just over 300..... I only had 10 minutes but will have another look tomorrow.
Guitar amplifier builder and avid electronics nut

My channel - https://www.youtube.com/channel/UC-WfLk ... 2jVvDeDqBA

Cowasaki Audio