N.Pass B1 Buffer DIY preamp!
Danilo's post on a thread in April got me checking into simple N.Pass preamp designs, and I built a pre-amplifier from an Alps Blue Velvet pot and a B1r2 buffer that uses JFETs in a push-pull config. Amazing! For just a handful of parts I'm getting some pretty amazing sound, which beats a lot of what I've heard including, to my ears, the Glasshouse Seiden Takman Rex kit.
Really silent and sound emerge with a natural ease. There are good details and imaging, even at lower volumes. There is just such a musical-ness and breath of life in its presentation, a realistic sense of space between the musicians that doesn't seem to be just about staging depth and separation. I also got a bit more bass, low and high bass, so had to move the speakers a little to rebalance with the room.
I put it in a biscuit tin for my proof-of-concept phase, powered from a SMPS laptop supply and a simple voltage divider to get +10v/-10v. A few experiences with the biscuit tin: being flimsy, chassis vibration is a delicate issue. With no damping, things were just a bit nervous and congested in lively, complex music. Add some Silent Coat 2mm butyl-based damping and everything went a bit over the top in the euphonic department, but lost all the harmonics and leading edge of sounds. Dropped back to just two 1cm squares with a little experimentation on placement.
And tis is all with a basic Alps Blue Velvet. I haven't even gotten to consider fancy attenuators yet.
It's sounding pretty good now, way better than I could imagine for the cost and use of an SMPS, but it's time to put in a proper enclosure and build a proper linear supply and see what that does to the sound.
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Bruce
Theories are not so much answers as questions, to be supported or undermined by experience & testing.
Source: Audiolab 6000CDT > Calyx 24/192 DAC
Amplification: Pass-design B1rev2 pre-amplifier > Neurochrome Modulus 686.
Loudspeakers: Proac Response 1SC
Cables/stands: spkr: MIT MH-750 biwire; IC: HT Truthlink; Target stands, sand-filled; Excel Cat6A 23AWG UFTP & 1attack.de Cat.7 SFTP.
Other: Balanced AC transformer to hydra mains distr; Bass traps & Acoustic panels; Isolation: Inner tube & roller bearings; 3xZyxel ES104A switches in series w/Vreg upgrades.