Question about Hiwatt DR103 preamp

[lrgaraujo]

Hi guys,

I was studying this schematic
https://hiwatt.org/Schematics/DR_Pre4Input_v2.pdf

and was confused by the second triode of V3 (pins 1-3)? What is it doing?

Thanks

[davent]

I believe a cathode follower, high impedance buffer before the phase inverter (PI).
dave

[lrgaraujo]

Cool, thanks!

Lourenço

[danfrank]

Actually, it's a low impedance buffer for bias for the phase inverter. Signal comes from the first section of V3 (pins 6,7,8) to the phase inverter but the phase inverter derives its bias from the second part of V3 ( pins 1,2,3). Makes for a super clean signal at phase inverter. A big reason why HiWatt amps are as clean sounding as they are.

[lrgaraujo]

Actually, it's a low impedance buffer for bias for the phase inverter. Signal comes from the first section of V3 (pins 6,7,8) to the phase inverter but the phase inverter derives its bias from the second part of V3 ( pins 1,2,3). Makes for a super clean signal at phase inverter. A big reason why HiWatt amps are as clean sounding as they are.

Cool, I can see what you mean! Thanks