It relies on the local-feedback resistors around the 47 output tubes to set the gain of the 6AU6 pentodes in the input section, which in turn are only lightly loaded by the very small capacitance of the output section.
In fact, if the 47 pentodes are connected as triodes, or in an ultralinear connection, the advantages of the circuit disappear. Unlike the prevailing SET all-triode trend, this is an all-pentode all-differential design that exploits the low capacitance and high speed of pentode circuitry. Gary Pimms's unusual PP47 amplifier has gotten a lot of notice in the Tube DIY Asylum recently especially since the operation of the circuit isn't at all obvious from the schematic. Gary Pimm (on the left) and his PP 47 DHP amplifier I'd say it was a safe guess that I heard 50 to 70 years of engineering experience in that meeting alone. Not everyone agreed - indeed, there was spirited disagreement at times - but the process of disagreement was illuminating for this listener, revealing the life experiences, technique, and way of thinking of all three designers. I can't think of any hifi show in the world where three world-class transformer engineers would be meeting in the lobby - on the first day! I felt privileged to be there, and listen in on the discussion. The high-energy discussion drew in several other audio enthusiasts, including Ben Reginato, head of the Bay Area Tube Enthusiasts.īen Reginato (left) and John Atwood (right) On Friday, first day of the show, there was a mini-conference about transformers in progress in the lobby of the hotel, with Tom Hodgson (published in Sound Practices #4), John Atwood (former Tech Editor of Vacuum Tube Valley, now head of One Electron), and Bud Purvine (transformer designer for O-Netics in Everett, Washington). What follows is my personal experience of the VSAC - the Valhalla for the outer limits of the audio world, vacuum-tube engineers, designers, and hard-core enthusiasts. Well, no Vegas showgirls here, you'll have to go elsewhere on the Internet for that. Imagine hundreds of Italian-suit marketing flacks, nerdy engineers, Stereophile reviewers, guys with slicked-back hair dressed in New Jersey leisure suits smoking cigars, and well-endowed Las Vegas showgirls all jammed in the same hallways. This wasn't just weird, it was downright freaky. Their rooms were one side, we were on the other. (Hey, you think that was bad, the previous year the porno dudes shared the same hallways as the high-end CES crowd. I think that was the year I wandered away from the high-end ruckus and discovered that the Adult-Video part of the CES had moved to the other side of the Sahara hotel. You can imagine the appalling effect on the sound of equipment.
THE TUBE PREAMP COOKBOOK ALLEN WRIGHT WINDOWS
I remember one year at the Sahara Bi-Level in Las Vegas when the power was so unreliable that the show organizers had to rent a collection of construction-sized generators, park them in the parking lot, and run 1" thick power cables through partially open windows into the rooms. Sometime you roll the dice, it sounds good, sometimes not, and sound that changes from hour to hour isn't unusual in small hotel rooms with just-barely-adequate power. I know from hard experience (as a CES exhibitor) good sound at a hotel-based show is more a matter of dumb luck than anything else. You'll travel along with me as I chat with the designers I spent little time listening, mostly schmoozing and taking photos. What you'll see here is a personal impression of the 2003 VSAC show. They also cover the entire show, room by room, giving a virtual tour of the show. These are reports written from a consumer perspective what's hot, what's not, lots of photos, what the audio-reviewer liked best. You've probably already seen the show reports from The 2003 show attracted manufacturers, engineers, designers, and enthusiasts from all over the world.
But going pro, at the VSAC, doesn't mean replacing engineers and designers with marketers. People who start off in the Craftsman's Room frequently "go professional", like Josh Stippich, and have their own demo rooms two years later. Unlike the CES, which is a marketing-driven trade show for hifi dealers, the VSAC, originated and organized by Dan Schmalle (aka Doc Bottlehead), is a show for vacuum-tube enthusiasts.
Josh Stippich hits the Big Time with the Electronluv 801/2A3 amplifier. VSAC 2003 Vacuum Tube Valley VSAC 2003 Show Report