Pass B1 preamplifier.

I’ve been working on a preamp based on the B1 buffer designed by Mr. Nelson Pass. It’s using two pcs 2SK170 per channel and from what I understand it operates in Class A.

The pcb is fully populated and I just recieved the 20K stepped attentuator.

I’ve used 10000uF/25V Dubilier caps, 1uF MKP’s (3pcs) and 12uF Jantzen cross-caps.

This is how it looks now.

I have a Regulated linear +18Vdc PS made, but I’m thinking of using a SMPS wallwart (18V/1A) to save space and be able to use a smaller chassi for the preamp.

Got the box for this preamp today, it’s a cute little box. 235x150x80mm, which is perfect.


Drilled holes in the backplate and fitted all connectors, but as you can see I really shouldn’t measure by eye…not really symetrical.


Mounted everything except the fuseholder in the box. Left to do now is internal wiring and mounting the fuseholder.

I’ve also soldered silverwire in PTFE tubing between RCA-inputs and the B1 PCB today.

2×0,6mm silverwire for signal and 2×0,6mm silverwire for ground.

2012-04-14 (my mothers birthday btw 🙂  )

Fitted a fuseholder to the backpanel, was alot more work then I expected since I didn’t own a big enough drill and had to widen the hole with my Dremel.

Got some more internal wiring done. Tried to keep it neat and away from the PCB.

I did the wiring for the input selector and volume attentuator too, but now I’m taking the rest of the day off.


Internal wiring done. Just waiting for the PS to arrive and I’ll need to order some 200mA slowblow fuses.


Today I got the external +18VDC/1A powersupply 🙂

Now I’m just waiting for some 200mA fast blow fuses that should arrive this week.



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