Pass Labs B1 preamp build

[blackraven]

Well, we completed the B1 and it sounds awesome in my son's system tonight. He is running it with my old Parasound A21 amp, PSB B6 speakers and a laptop computer using Bug Head and an Audio Quest Dragon Fly DAC with an AQ Jitterbug. The sound has excellent air and transparency with a wide sound stage. The background is very black and the clarity is amazing. Bass is tight, controlled and powerful with just a little bit of bloom. The midrange is very smooth and liquid but detailed at the same time with very good texture. Midrange and clarity seems to be its strongest point. Vocals, horns and piano sound real and alive. What really surprised my was how dynamic the sound is with it being basically a buffer with no gain. If I had to pick a weakness, I would say it is that the very upper frequencies appear to be pushed back or slightly rolled. That may improve as it breaks in over the next 50 hours or so. If it doesn't, I may replace the carbon Riken resistors in the output stage which were used there to lend a little warmth. But I have read that they can roll off the highs a little.

I have a friend who is an EE and he helped wire in the selector switch. He put the preamp on a scope and it spec's out well. The square wave was pristine and the frequency response was spot on 20-20K. I think that you would have to spend at least $1500 or more to get this kind of performance from a preamp. Overall it took his system to a new level of audio sophistication.

Next up is to get rid of the wall wart power supply and add a torroidal transformer and a remote volume control.

I built the preamp with about $300 of parts (the chassis and shipping was $110 and the boutique Mundorf and Clarity ESA caps ran about $100) but it could easily be done for about $150.

I will post pictures on Friday when I have the day off. I will also try the preamp in my reference system and compare it to my BAT preamp and report back.