Crown IC150 Phono Stage

Someone asked me how I fit the Jung-Didden regulators into this box...which led me to look at the phono section.

The two input transistors that Crown used, 2N3895A and PN4250A low Rb, the LM301A opamp is truly ancient. I hadn't seen this type of phono-pre, but only started seriously dabbling in phono pre and RIAA comp networks in the past decade or so!

SY isn't around to throw bricks at this Crown design. The compliance, in simulation, to the RIAA curve is very good. Will have to see if my actual living model is equal to the simulations.
 

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It's a bit disappointing that Crown did not exploit one of the LM101 (milspec) / LM301 (commecrial grade) opamp's greatest features: EXTERNAL COMPENSATION. It gave board level circuit designers tons of flexibility. Application brief LB-4 discusses a few possibilities, and the datasheet discusses a few more.

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I believe you got the schematic wrong. The 732K resistors connect to the emitters. I loved the 2N4250 transistor when it first came out. It was probably the best cheap low noise transistor available. It would run with microampere collector currents and still had good beta. Many transistors had severe beta loss at low currents.
 
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Deane Jensen used the PN4250A as the 2nd amplifying stage ("VAS") of the JE-990 discrete opamp, and bragged about how good it was. But his design required a transistor that performed even better than the 2N4250 datasheet spec registered at JEDEC. So he ran a little mini-qual to find vendors who routinely beat the spec by enough margin to satisfy Deane Jensen. He found that Fairchild and National Semiconductor's PN4250As did. Both of them.

Nelson Pass also designed the 2N4250 into several of his Threshold products, including the NS10 preamp of 1978.

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I believe you got the schematic wrong. The 732K resistors connect to the emitters. I loved the 2N4250 transistor when it first came out. It was probably the best cheap low noise transistor available. It would run with microampere collector currents and still had good beta. Many transistors had severe beta loss at low currents.
I agree. The 732K provide DC feedback to the emitters.