The Hafler 110 which I purchased almost 30 years ago needed an update to the RCA connectors. I decided to take out the "Model 112 Pre Preamplifier" and traced it out. Uses the now unobtanium 2SB337 and 2SD786 for a gain of 20dB:
An externally hosted image should be here but it was not working when we last tested it.
Those were Erno Borbely's favorite bipolars -- something like 0.55nV/Rt Hz. You could use 2N4400/4403.
The circuit works well, but doesn't sim well! Marsh had done something similar in 1982, and Leach in 1999.
I had it on the bench out of its steel enclosure and THD% was negligible. I am going to assume that they matched the transistors for small signal gain. It would be easier to buy a bag of 100 of the 4400/4403 and match than to buy (probably fake) B337/D786
The circuit works well, but doesn't sim well! Marsh had done something similar in 1982, and Leach in 1999.
I had it on the bench out of its steel enclosure and THD% was negligible. I am going to assume that they matched the transistors for small signal gain. It would be easier to buy a bag of 100 of the 4400/4403 and match than to buy (probably fake) B337/D786
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