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udip 21st January 2005 09:57 PM

990 discrete opamp
Hello all !!;)

I'm kind a new member on this forum, but I must say I find
this forum very interesting. One can learn a lot from people
in this forum.....and it's very good to read as many opinions as possible on a subject. :spin:

I'v read a lot about discrete opamps in this forum, and many
has mentioned the JC-2, Elektor preamp, Great River... but I
can't see a thread about the 990 opamp (The one that is sold
by JH company, and if I'm not wrong was developed by Jensen).

Is there a reason for that? Did anyone buy/build this opamp
or had a chance to listen to it? How does it compare to
other discrete designs?


udip 21st January 2005 10:09 PM

I'm sorry...the link:

john curl 21st January 2005 10:32 PM

It is a pretty good discrete op amp, but somewhat dated. Fet's on the input 'improve' the initial design.

udip 21st January 2005 11:02 PM

Hi John,

Do u think that fet's on input will do better?
I suppose it is designed for minimum noise with low impedance
sources, so bipolar inputs seems ok, no?


studiotech 21st January 2005 11:11 PM

Don't forget Forssell
Check out Mr. Fred Frossell's design here:


I have a line level pre built with these....wonderful!


udip 21st January 2005 11:19 PM

Hi Greg,

Are you talking about the JFET-992 or the DLR-1??

studiotech 21st January 2005 11:33 PM

the 992 to be exact.

I could post some pictures maybe tomorrow of my design.


udip 22nd January 2005 03:39 AM

Has anyone tryied this discrete jfet opamp from forssell??

Simple class a jfet opamp

udip 22nd January 2005 03:41 AM

It looks so simple...I wonder how does it compare to a good
IC opamp like AD825 or OPA627....

studiotech 22nd January 2005 05:39 PM

It IS simple, but the difference is in the power supply that you can operate it from. Being able to go all the way up to +-24v gives LOTS of headroom. The original design for the pre that I built was used in a pro +4dBu environment for a mastering engineer, mine however is only for home use, so maybe it is overkill, but that's what I like!


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