MV692 fet

[Moby]

Hey guys, I have to repair it and  to save some time i ask did someone here find the best replacement fet for this guy? As I can see from the sch bias is controlled under the 29-25 "chip", so presume that it have to be choosen from a batch for the optimum noise/dist operation. Any experiance to share?

 

[Gus]

found this
http://www.hifi-forum.de/viewthread-71-6013.html
No W
http://www.datasheetarchive.com/dlmain/75793c7f1080dc2df32cbfe5c8fcc8a115c32a/M/KP303E

http://www.radiomuseum.org/tubes/tube_kp303.html

Also looks like there are some for sale on the web

 

[archdakemkII]

I have a spare 692 circuit board I don't need except from the transformer. Do you want me to desolder the fet and send it to you?

 

[Moby]

I have a spare 692 circuit board I don't need except from the transformer. Do you want me to desolder the fet and send it to you?

Hey mate thx. No need, originally on this board the one is bc264b (i have a spare)  it's later MG production.  I wonder did someone sucesfully  replaced it with lower noise (read sonically  better) one???

 

[Moby]

Also, a bit off topic thinking... does the lack of transient (i hear it that way) is caused by 29-25?  I tested the MV692 alone and it seems that its really "rounded" or slightly  low passed from 15khz

 

[archdakemkII]

I think the frequency response above 15KHz if affected mainly by  the transformer. I am not convinced the a faster FET will make the mic sound better and I don't think the noise performance of the 692 is an issue but again my experience comes from using it with a UM70 large diaphragm head and not with the SDCs.

If you are in the mood for experiments, try taking the transformer out of the circuit. Personally I like the roundness...

 

[Moby]

I think the frequency response above 15KHz if affected mainly by  the transformer. I am not convinced the a faster FET will make the mic sound better and I don't think the noise performance of the 692 is an issue but again my experience comes from using it with a UM70 large diaphragm head and not with the SDCs.

If you are in the mood for experiments, try taking the transformer out of the circuit. Personally I like the roundness...

right, I started to think about this based on my Neumann tx knowledge, but yes, it can be the issue. Good one. I like to mess with transformers

 

[AusTex64]

I recall Oliver Archut commenting on "the crummy FET and transformer" used in the GDR produced MV691/692 . He certainly believed there was much room for improvement.

 

[Moby]

Ok, regarding TX , I will check. But still wonder about the fet