Aunt Corey's Homemade Buffered Passive Preamplifier Mo' Better Mods, Page 4

Lather knows best
You want lather? I'll give you lather; when I changed the Alps pot out for the Penny & Giles, the preamp sounded more open on top. When I installed the high-speed rectifiers, the low-level detail became much clearer and the slight grain through the mids was banished. When I rewired the audio circuit with Kimber silver wire, the sound became even more alive.

But when I installed the dual-regulated power supply, the preamp was transformed. Bass lines just bounced out of the BUFs, deeper and tighter than I'd ever heard them over the mighty Muse subwoofer; the sense of increased "slam" was amazing! I mean, this preamp BOOGIED! And the sense of recorded space on purist recordings like the Cowboy Junkies' Trinity Session and JA's piano cut on the first Stereophile Test CD was just incredible; so much better than the original prototype, I could hardly believe this was the same preamp. The increased sense of bass boogie made music sound much more rhythmically exciting, even slow blues like Stevie Ray Vaughan's "Tin Pan Alley." Is this what real hi-fi critics like Mr. Martin Colloms mean when they talk about "pace"? If it is, boy, then "pace" is IT!

John Curl, thank you; dual regulation transformed my preamp from a very good piece of gear into a serious monkeybone muh-cheen. Yeah, it was a pain in the butt to go back and rebuild the power supply, but the improvements it wrought are on a par with installing dedicated AC lines in my listening room. It's that dramatic, and I'm that ecstatic! (footnote 11)

Aunt Corey's advice for the lovelorn
I figured a number of people handy with a soldering iron would build my preamp, but the response thus far has been amazing; there's more of you freakazoids out there than I dared imagine! One guy even built a buffered preamp for his car, powering it off the 12V battery under his hood! I alerted the local authorities immediately, who assure me that, though his condition has been steadily improving for weeks, the word "ointment" still sends him into paroxysms of fear.

Many of you wrote that you had trouble finding BUF-03s. In response to the original article, parts king Michael Percy is now carrying the FJ commercial versions of the BUF in his catalog, for 12 clams apiece. I use the AJ milspecs, but the FJ will work and sound just fine at a much lower price. The AJ was designed for extreme military conditions like that helicopter attack scene in Apocalypse Now, where they tear-ass over the village blaring Wagner over their Tiny Triode-driven Klipschorns; for my preamp, the FJ version is more than adequate. Ever hear a Theta processor? You've heard BUF-03FJs. 'Nuff said.

Sources of supply

• Newark (Motorola MUR-810 high-speed rectifiers): look in your local Yellow Pages for the Newark distributor in your town, or just call (312) 784-5100 for the Newark nearest you. Newark is a parts distributor, not a manufacturer, so technical questions about these and other parts will fly over their heads like so many Canadian Geese; order from them, but get the techno-jizz from the manufacturers.

• Penny & Giles: 2716 Ocean Park Blvd. #1005, Santa Monica, CA 90405. Tel: (213) 450-9860, ask for Neal Handler. P&G makes tons of different parts; mention this article, and he'll steer you to the right pot.

• Michael Percy (BUF-03FJ): P.O. Box 526, Inverness, CA 94937. Tel: (415) 669-7181.

Your buf keeps lifting me hiiiiiiiiigher
One thing that kept intriguing me throughout this whole upgrading game was that I never really got to the point where the sound stopped getting better; the upward "YEAH!" curve never flattened out. What this tells me is that the BUF-03 is capable of even better sound than I thought it was, and that its potential is just now being tapped. I had a lot of respect for this li'l buffer before, but I'm eager to see just how far it can be taken before it becomes the bottleneck of the design. And if you run across any tricks 'n' tweaks, drop me a line here at the mag (footnote 12) and turn me on. Ask not what your BUFs can do for you, but what you can do for your BUFs!

If you've already built Aunt Corey's Homemade Buffered Passive Preamp, these mods will make a good preamp great; if you haven't built it yet, I hope this new article helps you do it up right from the git-go. Now, pull those shades down and GO CASPAR GO!

Footnote 11: We plan a review of CG's buffered passive preamplifier in the near future.---JA

Footnote 12: Write to CG at Stereophile, P.O. Box 5529, Santa Fe, NM 87502, Fax: (505) 983-6327, with "Modkateer Fever" written prominently on the envelope or Fax cover sheet.---JA