Wanted. Someone to redesign a vas stage of a amp

Ryan0348

Member
2019-08-20 6:48 pm
im looking for someone that would he willing to redesign a vas stage of a amp to use tubes instead of the bjt that it currently uses. Pay of course. If you interested please let me know. Im sure it might be silly but i have quite a few of these mosfet monoblocks and im currently using a 6922 tube preamp on the unity gain ouputs and i really like the sound. Seams like ot would sound better have a tubes go directly into the mosfet output stage vs through bjt's then onwards. Thanks.
 
I will write what should be obvious.

Tubes and transistors work on different physics principles, which means, there can be behavioural surprises when one swaps tubes with transistors. I am assuming one makes all the necessary changes for correct biasing.

My suggestion is to explore other types of transistors instead of restricting yourself to valves. There are many different types of transistors which work on different principles.

My suggestion is to try a Junction Field Effect Transistor. Like a valve, this requires a negative bias on its gate. I never tried it and it may cause unwanted surprise effects like added random noise and other signal impurities.
 
i'm using 6922 as a preamp for a 80w low gain SS mosfet amp. works great

as for using a 6922 or eq. for VAS you need the following.

1 . two negative VAS rails and one positve ie. 45v and -60v and -70v
2 . switch on positive VAS rail ( no positive drive until tube is warm)
3. Triode "constant current source" on positive rail
4. DC filament supply

are you going to use tubes for the differential inputs or BJT or J-FETs?