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ak4396 5th March 2010 03:14 PM

D1 with high transconductance FET?

Did some body tried a high transconductance FET like the IRF3205 (gfs = 44S) in the I/V stage. The IRF 510 sounds also better than the 610.
The 3205 have much more input capacitance. But I think this is not a problem in that kind of circuit.

Is it?


Nelson Pass 5th March 2010 06:05 PM

Perhaps you should try it and see.


ak4396 19th March 2010 02:53 PM

listening tests

I did some listening tests the 510 is still my favorite! The 3205 is not so bad maybe one step with the 610.

I have the 540 and 540N on my list.

I want to try some other parts.
What are the good values I have to look for?
Maybe low Vgs?


h_a 19th March 2010 04:12 PM

The usual: high transconductance with low capacitances - but these keep coming together so it's as always a compromise ;)

Low vgs and low rds-on are of no real interest.

Have fun, Hannes

Ipanema 19th March 2010 05:42 PM

How about power D1 as current source amplifier?

Nelson Pass 19th March 2010 07:06 PM


Originally Posted by h_a (
The usual: high transconductance with low capacitances

Actually, the circuit is pretty tolerant of capacitance.


h_a 20th March 2010 07:51 AM

Good to know! I thought the DAC in the D1 is current driving the fets, so the little output current may be happy to see lowish capacitances.

Have fun, Hannes

samoloko 22nd March 2010 12:57 PM

this might be of Interest
It Is Interesting that guy has excluded In final development the buffer stage

would anyone be nice and explain the purpose of 2,7 nF caps - what type Is best here, can I use 2,2 mkt


samoloko 29th April 2010 06:42 AM

any updates
Is irf510 still your winner
did you replace only I/V FET or both
are you using original schematic
what Is your out cap

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