5670 Soul Sister C4S

C

calsaint

New member
Hey hey !
Been a while for this formerly pretty active poster. Hope everyone's doing great.

So I built a 5670 Soul Sister as posted in the Valve archive and have a question about the plate voltage.
I've got series 0D3 feeding the C4S 300v , 330R rk
The schematic suggests I should have 150v at the plate, but I'm getting like 230v. Is this just something I can expect to be a little up in the air given the 5670 I happen to have in the socket ?
Pre sounds great, it was fun to build something again.

Thx gang as always
-Steve


 
100 Ohms as your C4S R1 with HLMP-6000's will give just under 9mA.  9mA through the 332 Ohm cathode resistor will give you roughly 3V of bias. 3V of bias and 9mA gives you a plate voltage closer to 200V than 150V.

Take out the 332 Ohm cathode resistor and install an HLMP-6000 on each channel (stripe to ground) and you should be between 140 and 160V on the plate, you'll get a little more gain, and I bet the preamp will even sound a bit better.

-PB

(PS - welcome back!)
 
The spec sheet lists the operating point as 8.2mA, 150v, with 240 ohm cathode resistor (2v bias). The original schemo (VALVE 1998 v5n4) has some errors. Just some FYI.
 
good stuff here PB and PJ.
many thanks as always - the BH team is really the primary reason I have a cool system and a cool hobby.

-Steve
 
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