Is this a Pass preamp?

[george a]

Hi All

I stumbled across the attached schematic - is it a Pass preamp -if so which one?
Thanks in advance

 

[Dennis Hui]

It looks like the core of the Aleph L linestage.

 

[Zen Mod]

definitely all blocks made with Papatricks

though, I can't relate it directly to any of PL or DIY Papaworks

 

[george a]

Dennis - You appear to correct ..
have looked up the Aleph L linestage - and that's pretty much it

Thanks

..I'm trying to decide what preamp to build...

 

[dliscomb]

C102?? 😵

 

[Extreme_Boky]

You dislike the C101 for some reason?

 

[george a]

Not sure what the issue with c101 or c102 is ,,,?
both 10uf....?

 

[ra7]

I see schade feedback with a CCS load and AC load through R31. Intrigued by C104.

 

[Mark Johnson]

I don't think Nelson ever used an enormous slugg-em-in-the-nuts capacitor like C103 (680 uF!) in any of his constant current source designs.

The low frequency rolloff introduced by C102+R31, is at an uncharacteristically high frequency. Usually NP picks BIG output capacitors giving a rolloff below 0.5 Hz. 10uF at the output? Not his style.

Finally the PNP is a cheesy Motorola jellybean part? That's not Nelson's style; he normally uses Toshiba or Zetex BJTs. I'd expect to see something like 2SA970BL or ZTX795A.

 

[wayne]

Not a Pass drawn schematic. MPSA92 would have been very early or Threshold days.

 

[Osborn]

This is a PL20, just drawn a bit differently. 680 uf et al.

 

[Nelson Pass]

I use 4739's like gumdrops, it's probably based on one of mine....