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Old 21st January 2005, 09:57 PM   #1
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Default 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.


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?


Udi.
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Old 21st January 2005, 10:09 PM   #2
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I'm sorry...the link:
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Old 21st January 2005, 10:32 PM   #3
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It is a pretty good discrete op amp, but somewhat dated. Fet's on the input 'improve' the initial design.
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Old 21st January 2005, 11:02 PM   #4
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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?


Udi.
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Old 21st January 2005, 11:11 PM   #5
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Default Don't forget Forssell

Check out Mr. Fred Frossell's design here:

[URL=http://www.forsselltech.com/products.htm]

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

Greg
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Old 21st January 2005, 11:19 PM   #6
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Hi Greg,


Are you talking about the JFET-992 or the DLR-1??
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Old 21st January 2005, 11:33 PM   #7
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the 992 to be exact.

I could post some pictures maybe tomorrow of my design.

Greg
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Old 22nd January 2005, 03:39 AM   #8
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Has anyone tryied this discrete jfet opamp from forssell??

Simple class a jfet opamp
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Old 22nd January 2005, 03:41 AM   #9
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It looks so simple...I wonder how does it compare to a good
IC opamp like AD825 or OPA627....
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Old 22nd January 2005, 05:39 PM   #10
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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!

Greg
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