Ferrite bead on FET gate.

[k brown]

The classic Schoeps circuit shows a ferrite bead on the gate of the FET - would that be advisable on any mic FET, or is it something needed more with a capsule that's not grounded? It isn't seen on vary many other mic schems.

 

[Bo Deadly]

I'm not sure what that ferrite is for. The whole thing is screened from RF so I don't see why it would be needed. Maybe it's for when it's open and on the bench for testing. Trying to add a ferrite is problematic anyway because usually the gate is not soldered to the PCB. It's just soldered directly to the bias resistor and capsule lead. At least in a DIY build it is. Ferrites on pins 2 and 3 would be more likely to be useful.

 

[k brown]

Interesting notion - just there for when setting bias of the FET?

I think the Schoeps also has ferrites in those positions as well.

 

[rogs]

Could be for extra RF suppression when used with the active cable which remotes the capsule from the preamp? ... KC | SCHOEPS Mikrofone

 

[abbey road d enfer]

Could be for extra RF suppression when used with the active cable which remotes the capsule from the preamp? ... KC | SCHOEPS Mikrofone

You beat me to it!

 

[k brown]

Ah - hadn't thought of that.

 

[moamps]

Ferrite beads are used to ensure the stability of the amplifier/impedance transformer also.

 

[Biula]

The classic Schoeps circuit shows a ferrite bead on the gate of the FET - would that be advisable on any mic FET, or is it something needed more with a capsule that's not grounded? It isn't seen on vary many other mic schems.

Stops possible high frequency auto oscillations...

 

[bremusound]

I just found a hint about these ferrite beads on the web, it shows that the
Bourns FB43-110-RC has the proper dimensions.

https://billthompson.us/bt/schoeps-mic-conversion/