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Question about Hiwatt DR103 preamp

Started by lrgaraujo, June 25, 2020, 10:05:13 PM

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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
"If you always do what you always did- you always get what you always got." - Unknown

If my photos are missing again... they're hosted by photobucket... and as of 06/2017 being held hostage... to be continued?

lrgaraujo


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

Quote from: danfrank on June 27, 2020, 06:07:29 AM
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