Son of Ben bias voltage

[mimosa]

on Son of Ben, looking at the schematic and instructions for the various trimmer adjustments:
- Trim1, can I replace R5 with a 12K (1%) and remove T1 all together?
- Trim 2 and trim 3: can I remove R9 and R12, along with T2 and T3, and replace VCC with a direct 4.0V supplied voltage say VB that the power section would set for 4.0V (using resistor divider 120K/270K for example, of course adding filter caps not shown)? How critical is to get 4.000000V, assuming a specific power supply brick may also vary from one user to another anyway.

 

[temol]

You need a resistance there.
You can replace all the trimmers with jumpers and set the drain voltage only with resistors R5/R9/R12.
R5 - 12k, R9 and R12 between 18-22k depending on the transistor parameters.
4V is not critical. I suppose that anything between 3.9-4.2V would be ok.
Or just set the voltage by ear. If you like 4.5V then leave it as is

 

[mimosa]

thanks for the answer, looks like I can get away with R9 and R12 using 18K and a 5K trim pot. Would be finer adjustment than the 50K one at least

 

[temol]

I'd go with 15k + 10k trimmer
Remember - it's not a rocket sience, your'e not sending a rocket to the moon. 4.0000V or 4.0134V...