Aunt Corey's Homemade Buffered Passive Preamplifier Mo' Better Mods, Page 1

Mo' Better Mods
Stereophile Vol.15 No.11, November 1992
Corey Greenberg revisits his Homemade Buffered Passive Preamplifier (footnote 1)

"Dad-blamed Postal Service!" Elvis fumed, shooting up a Mitsubishi big-screen TV with his blue .357 and taking a pull off a Big Red. "Mah one chance tuh be awn a genyoowahn US stamp, an' they got me lookin' jes' like some cleenteen WIMP, man!" A smoking shard of the big-screen's control panel fell earthward. Elvis whirled, blew it into dust before it hit the ground.

Why was the King Of Rock And Roll in my dreams again? To holler about the "young Elvis" image we all voted for this past April in the big competition to choose which likeness of Elvis would grace his commemorative stamp. I voted for the "young" portrait mainly because it was closer to the Sun Sessions '54 Elvis than the white jumpsuited Vegas-style stamp representing the "later years," but I agreed with my King: the young stamp made him look too clean, too polite. To paraphrase the holy Greil Marcus: 15 years after his death and they were still shooting Elvis from the waist up.

"What 'bout 'Jailhouse Rock'?! Hail, that woulda made a FAHN stamp, man! Now they got me lookin' lahk some pink poodle Pat Boone PANTYWAIST!!"

He paced back and forth through my dream, furiously throwing karate chops into the air and snarling at the heavens. I spoke to him.

"I couldn't agree with you more, El. They boned you, man! If it'd been up to me, I would've had a stamp of you during your '68 comeback TV special; you know, when you wore that bad-ass black leather outfit and sat around with all your lackeys, gunning through your old tunes like it was 1954 all over again. It was your finest hour."

Elvis stopped and stared at me. A lone crystal tear rolled down his cheek into his immaculate sideburn. He walked over and placed his hand on my forehead.

"Corey," he said, his voice breaking just a touch, "It really don't matter what fool portrait they choose---hail, let 'em put out a 'Harem Scarum' stamp fer all Ah care! Cuz if there's jes' one young fella on Earth with as pure a heart as you, son...then Ah kin finally take mah Eternal Rest."

His smiling image began to slowly fade into the mist. I cried after him. "But Elvis! I didn't get a chance to tell you about the mods I made to your buffered passive preamp yet!"

The faint image melted into nothingness, as his reverb-soaked voice came from far away: "Return to sender...address unknown..."

Then he was gone.

If it ain't broke, keep messin' with it
When I first designed and built Aunt Corey's Homemade Buffered Passive Preamp (footnote 2), I just slapped the thing together and listened to it. Sounded good! Real good, in fact. So good, I brought it over to Austin high-end retailer Audio Systems to compare it with their best Class A-ranked preamps. To a room full of hi-fi salesmen and various hangers-around, the prototype Aunt Corey's Preamp was clearly a notch above the others, offering a much cleaner, more tightly focused sound. The clarity through the mids and highs, in particular, was exciting enough to create an instant clamor among the assembled audio nuts for more Homemade Buffered Passive Preamps. Me, I was just excited that something I'd built worked, much less sounded good.

Because my preamp worked so well right out of the chute, I left it alone (footnote 3), happy to rediscover all my favorite recordings in all their newfound clarity. I'm hardly an inveterate tweak; you won't find me hunched over the workbench at 4am, listening to different resistor polarities to see which one gives the most temporal palpitude. That's for guys like Steve McCormack (footnote 4); I'm into sleep, and plenty of it!

Meanwhile, across town, Audio Systems' Steve Giunta (footnote 5) was building his own Aunt Corey's Preamp, but with one crucial difference; while I'm a slap-it-together-and-run kinda guy, Steve is Mr. Precise. They like you to have a certain respect for precision when they hand out Aerospace Engineering degrees, I guess. He took the same Precision Monolithics BUF-03 metal-can buffers (footnote 6) and the same power-supply circuit, but tied 'em all together with a layout so clean and kosher you could listen to it on Passover; compared to my tangled nest of hookup wire, Steve's preamp looked like a lot better.

Unfortunately, it also sounded a lot better, dag-nab-it! And after taking Aunt Corey's preamp to Santa Fe for the 1991 Writers' Conference, where I clearly heard the YBA 2 preamp better it in JA's listening lair, I knew I had to go back and clean the ol' girl up a bit. She was good, but there was plenty of room for improvement.

Footnote 1: The original article, which included the circuit and power-supply schematics, constructional details, and sources for the parts specified, appeared in Stereophile, November 1991, Vol.14 No.11, pp.91-103. Letters on the overall design and discussion of the power supply appeared in Stereophile, February 1992, pp.15-20.

Footnote 2: The Semantics Police can kiss my ham on this one; my preamp is exactly that: a passive preamp that has been buffered; ie, a BUFFERED PASSIVE PREAMP. And if you ever find yourself sitting down to write a "Letter to the Editor" because you have a problem with the semantics of the title of a stupid DIY project in a hi-fi mag and godDAMMIT your voice needs to be heard, do what I do when I start taking all this stuff way too seriously: Go to a mirror and pretend your reflection is a good friend of yours. Then tell this "friend," out loud, just why it is you're peeved and what it is you plan to do about it. If seeing yourself complain about the semantics of an electronics project in a hi-fi mag doesn't embarrass you beyond unholy belief, then by all means get out that Garfield stationery and GO DOG GO!

Footnote 3: Contrary to what Peter advised in his "Ground Floor" column last February (p.77), there's no need for an op-amp to buffer the optional tape Record-Out jacks on my preamp. SW2 in the original schematic was a DPDT switch before the jacks, which allows you to disconnect the tape deck's record inputs when you're not making a recording. And you should ALWAYS flip the switch to disconnect your tape deck whenever it's turned off; many units present a wild and untamable load when powered down.

Leave the op-amps OUT of my preamp, and enjoy the cleanest Rec-Out circuit possible: one Penny & Giles volume pot and a silver switch.

Footnote 4: Best known for the beautiful photographs which adorn the classic Robert Lucas albums on the AudioQuest label, Steve McCormack also designs audio gear under the McCormack brand.

Footnote 5: Steve Giunta also designed the Audio Express NoiseTrapper AC powerline conditioners I reviewed in Vol.14 No.11.

Footnote 6: As is pointed out in this month's "Letters" column, I inadvertently mislabeled the pin-out of the BUF-03 in an answer to a reader's letter last February. Looking down at the top of the top-hat can, pin "1" is the one to the left of the metal tab, with the others following 'round to the one coincident with the tab, which is "8."---JA