Ultra-high performance, yet rather simple - hybrid and more!

Jump to Latest
#641
The VAS drivers directly drive the output devices in this amp so changing the pot or R29 will do the same thing for the outputs. I think R29 will also change bias on the VAS drivers themselves though. I've noticed the amp sounds better when it's warm. I'm not sure if it's the temperature of the output devices or the VAS drivers improving the sound. That's why I'm asking.
 
#642
Voltage over R41, R44 is expected to be 0.93V, giving us 9.3mA at that point.
From that current, 1.3mA goes through R38, supporting the cascode.
The rest 8mA - is VAS current.

In other words, to calculate actual VAS current - measure voltage over R41, R44, multiply by 10 and subtract 1.3 🙂

8-10 mA is good for driving the lateral FETs.
 
#643
I'm still a newbie at building amps. So pardon my ignorance. I'm having trouble determining what these parts or they aren't available to build this amp. For example the FETs aren't available with Digikey or Mouser. Any alternatives or suggestions on where to get them?

50R 64W100 Pot 2
10 64W100 Pot 2
1k RES500 4
470 RES500 8
0.1 5W Cement 8
2R2 RES700 2
FET 2SK1058 4
FET 2SJ162 4
BJT 2SA1381 2
BJT 2SC3503 2


I can find trimmer resistors but when I type in 64W100 POT it brings up only one item in Mouser. The other trimmer resistors that come up I cannot tell if they will work on the board. So I'm kind of stuck. A Bom with mouser #s or Digikey #s really helps if you want to get your amp out there ....

Thanks.
 
Last edited:
#646
With regards to resistors:

50R 64W100 Pot 2 - multi-turn trimmer
10 64W100 Pot 2 - multi-turn trimmer

They look like these ones:
Honeywell
Bourns

Just find the right values - 50R and 10R respectively.

1k RES500 4 - metal film, 1k, 1/4W, 1% resistor
470 RES500 8 - metal film, 470R, 1/4W 1% resistor
0.1 5W Cement 8 - cement, SQP type, 0R1, 5W, 5% resistor
2R2 RES700 2 - metal film, 2R2, 1W, 5% resistor

RES500 and RES700 are just "internal" marks, coding the power rating (RES500 = 1/4W, RES700 = 1W).
 
You must log in or register to reply here.
Top Bottom