Audio Research LS1 what are those FETs?

[gamerpaddy]

ive got a Audio Research LS1 that has some hissing on the right channel that goes away once its running for a while, i suspect one of the old fet's going bad.
unfourtainly they are painted over and just marked FET, White Orange in the SM

Does anyone know what model they are?


Also whats going on here? are they just using them as capacitors?

i may also get a new 6922 tube to see if its the problem

 

[egellings]

JFETs are being used as diodes, while the MOSFET is being used as a source follower to buffer the tube.

 

[audio king]

Nobody knows what type those FETs are except ARC, and they will not tell you. If they actually have them in stock, you can order them. They won't be cheap.

 

[Wiliks]

Have seen similar bootstrap in different arc schematic where they used generic 2x 1n916

I think whatever one high voltage diode will do… just use some faster one. No dark magic there… ohh or maybe, snake oil **** of some sort 😉

 

[jan.didden]

PN4114 can be used or one of it's equivalents. Not critical.

Jan