[sdiy] a question for the experts

James Patchell patchell at cox.net
Sat Apr 17 05:27:15 CEST 2004

I can't remember which polarity the AD821 was (NPN?  PNP?)...I assume you 
want it for and expo converter....and I see that you say SVF, so that 
probably means OTA's, which means PNP.....

For PNP matched pairs that are premium, the MAT03 comes to 
mind...(pricey)...I also have THAT120 Quad PNP arrays which I sell for 
$3.79 each.  They don't quite have the Vbe matching that the MAT03 has, but 
they are still pretty good.

If you are not so much worried about premium performance, there is the 
2SA798 (hope I got this number correct), which will do a pretty darn good 

KRL is the only company making the traditional wire wound tempco resistors 
I know of (Tel Labs no longer make the Q81K type....in fact, Tel Labs is no 
longer, I think).  Getting them is going to be another matter.  Several 
people have found other substitutes that are much more reasonable to 
find...in fact, somebody advertised just today or yesterday saying they had 
some tempco resistors for sale.

At 04:02 PM 4/13/2004 -0600, Michael Schulze wrote:
>Can someone recommend a readily available replacement for the AD821 
>transistor pair in the EN#37 SVF?
>Also - who's holding tempco resistors?  I need some 2k's!
>Michael Schulze
>Instructor of Audio Production and Electronic Music
>University of Denver
>Lamont School of Music
>2344 E. Iliff Ave.
>Denver, CO 80208



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