John Tucker/Doc Bottlehead UX-45 Parafeed Direct-coupled SE Amplifier

"...the lineage of that amp goes back to a lunch at some crummy Chinese restaurant in Vegas in 1997, during CES. JT and I had been looking over some of the competition, and while waiting for our chow mein we put together a design on a napkin that we felt improved upon one or two of the more radical designs we had encountered that day. I think JT still has that napkin." - Doc Bottlehead

"I remember hearing them at the very first VSAC-- and I was mesmerized with just how darn dynamic and unflappable the amp was--- I was stuned (sic) at the time. Kudos to John." - Mike LeFevre, Magnequest

Steve Brown (well-known Tube Head) and I each built one of these in 2006 after finding the Positive Feedback article that talked up it's virtues.

I decided to join my woodworking and amp building hobbies to create casework that complemented the "old time radio" tubes. The case is Padauk, finished with 12 coats of indivisually hand rubbed Amber Shellac that has aged from the original orange color to a decidedly 'antiquey' rich red/brown.

This 1.8 Watt amp was my mainstay until a few years ago, paired with a very high quality Passive pre-amp; just an excellent volume control and switch that filled a 15'x18' room with sound from 97dB speakers. Various active pre-amps by CAT, DeHavilland, my own hand and others also satisfied and were more dynamic but I kept coming back to the purity of the Passive.

Construction details include Gabon Ebony feet, Edison Price Music Post terminals, Teflon Tube Sockets, Audio Note silver RCAs, and a combination of annealed silver, Vampire copper magnet, and copper XLO wires arrived at after extensive listening and tinkering.

Electronics include Audio Note Tantalum and Kiwame resistors, Film By-pass caps, Obbligato Oil Parafeed Caps, and the active Constant Current Source based on a Gary Pimm design with a large heatsink. The one departure from the original circuit is the use of tube rectification.

The Magnetics begin with the well-tried and quiet Hammond 373BX Classic Series power transformer, separate Hammond chokes for each side, separate filament transformer then finish up with Magnequest BCP-15 Plate Chokes and Robin Hood Nickel Pin-striped Parafeed output transformers.

After the single power transformers the construction is entirely dual mono for exceptional channel separation.

To help ensure that your enjoyment will equal mine I am including my entire tube complement used during the last two years it was in service: late 1930s National Union and RCA Cunningham UX-45s, Bugle Boy 5AR4 rectifier, and Sylvania 5965 driver tubes

Here's Steve Brown commenting in an Audio Asylum thread soon after the completion: "I'll chime in and 2nd Bill's comments. Very nice amp. Amazing how much definition there is around the individual notes. We did make a couple of slight alterations, but the character is the same. The one significant change was adding some B+ bias to the heater on the driver to kill some hum. To do that we added a 39k 1w in series w/the 270k bleeder, and paralleled the 39k w/22uf, then ran that to pin 9 of the driver. That made this the quietest SET I've ever auditioned. The other change is that Bill made this a stereo amp, but built in dual-mono power supplies." 

Payment is by personal check or USPS money order; shipping after it clears my bank.