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Old 22nd July 2014, 05:26 PM   #3041
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Originally Posted by M Gregg View Post

I have no connection its just for interest..DIY990..
That Hairball Audio DIY-990 kit seems to be nicely made, with all SMD parts and pins already pre-soldered, etc. However, since they use a SOIC-8 dual for the input LTP, it's not possible to substitute other low-noise single BJTs instead. I'd have preferred the option of substituting a Japanese low-noise NPN, either through-hole or SMD, at the input.

It also uses the API2520 pinout, like the JE990 and most professional discrete opamps. That's fine for studio equipment upgrades, but rules out consumer equipment upgrades, which are almost all DIP8 (both dual and single).
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Old 22nd July 2014, 05:34 PM   #3042
M Gregg is offline M Gregg  United Kingdom
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I guess you couldn't adapt with something like this..


M. Gregg
What is the sound of one hand clapping?
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Old 22nd July 2014, 06:16 PM   #3043
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The API2520 pinout has a ground pin which is absent in almost all DIP8 opamps. It's possible to plug a DIP8 single opamp into an API2520 socket with a suitable adapter, but not vice-versa (apart from the size of the API2520 modules being much larger than DIP8).
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Old 23rd July 2014, 07:13 AM   #3044
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Originally Posted by M Gregg View Post
Just for fun..


Reminds me of the old philbrick nexus..Teledyne
Is this the same one? . . .
Yes, the API2520 had the same mechanical outline as the PP65 (circa 1964, "Model PP65A All Silicon Solid State Differential Operational Amplifier", http://www.philbrickarchive.org/pp65a.htm ) from George A. Philbrick Researches (often abbreviated as "GAP/R"). See "The Philbrick Archive" at http://www.philbrickarchive.org/ . Even though the package and pinout originated with GAP/R, it seems to be most commonly known as "the 2520" or "the API2520" package.

Other models, and other vendors - including Analog Devices, API and Opamp Labs - used the same package size and pinout for their products. In addition to John Hardy, I believe Pacific Recorders and a few other manufacturers produced 990-variants in that package.

The PP65A included a pin for Offset Trim; that pin wasn't always provided on other opamps in similar packages. Needless to say, a little investigation is essential if that offset pin is present on either the opamp module, or the circuit it plugs into. When I did the "Dunlop 2520" layout for the SWOPA (see Discrete Opamp Open Design ), I used that pin for the compensation node. I was quite aware that if standard offset-trim circuitry was connected to that pin, the SWOPA performance would be degraded.

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