Beezar Audio Millett MAX PCB Headphone Amplifier (without casework)

Description: This is a fully functional, populated PCB that will operate as shown in the photographs, as long as good tubes are plugged into the sockets and a 24VAC 1000ma, walwart is plugged into the amp. HistoryThis is THE original Beezar/TooleAudio Millett Hybrid MAX headphone amplifier, first designed in 2007. Its predecessor was designed by Pete Millett (find him as a seller here on Ebay!) and published in Audio Xpress Magazine in November, 2001, it became known as the "Millett Hybrid." Pete's original was not really designed for an enclosure, using only a plastic base with open PCB construction. Drew Dunn and Nate Maher further refined the design with what we called the "revMH Millett Hybrid." The revMH Millett Hybrid was designed for a standard Hammond enclosure and later incorporated discrete diamond buffers (Pete's original used the BUF634 chips) and linear-regulated power supplies. Because of this gradual evolution and improvements, though, the revMH also outgrew its original enclosure, ending up as a mix of various add-ons, rather than a refined, single package. Colin Toole next designed a larger PCB that incorporated the diamond buffers, the linear-regulated power supply, and even a relay-delay circuit to prevent power-on spikes. Beezar Audio joined with Colin to help design the casework and market the PCBs. The Millett MAX was born and as stated, this was the very first, fully functional Millett Hybrid MAX! Operation This MAX is an uncased prototype used for power supply noise reduction experiments, then placed in conditioned storage for many years at Beezar Audio. It is fully functional as presented, as long as good tubes are inserted in the sockets and a 24VAC 1000ma walwart is used to power the PCB. Since the tubes and the entire amplifier run at 24-27 VDC, there is little danger using this amplifier in the exposed PCB condition. (Note that a direct short could conceivably cause a fire if conditions are just right, so please exercise at least a minimum of caution in operation.) Placing the amp in a small cardboard box should be sufficient (supplied in shipping). The MAX PCB is the very same amplifier whose construction is photographed and explained in tremendous detail on the Millett MAX website! As with all Millett Hybrid-derivative amplifiers, the MAX PCB can use three primary tube types: 12AE6 tubes (high gain) 12FM6 tubes (medium gain) 12FK6 tubes (low gain) All of those tubes operate within 12-24V on the plates, with a maximum rating of 27V. NOTE: Because the MAX PCB, as with any other Millett Hybrid, was designed to use three different tube types with three different gains, you must re-bias the tube bias any time that you change tubes. You cannot swap out 12AE6 tubes for 12FM6 tubes, for instance, then not re-bias and expect it to work or sound as it should. The voltages of the tubes and bias are not the same. This is a simple procedure with use of a multimeter and the Bourns trimmer tool. (Full details are on the Millett MAX website and on the included CD with this sale.) The buffer stage of the Millett MAX is a true, fully-discrete diamond buffer using the Toshiba 2SC2238/2SA968 transistors. For those of you who know about audio quality BJT transistors, you will know that these are very sought after and rare transistors, with substandard copies rampant from China and India. These are the real, Toshiba transistors. The diamond buffer is biased to 50 ma in Class A. With the tubes biased at 13.5V, this gives a + or - voltage swing of 13.5V at 50ma. It will power most any 32 to 300 ohm headphone with ease, including many planar-type headphones. Parts Selection Only the finest parts have been used throughout: GENUINE Alps RK27 Blue Velvet 50K stereo volume pot Red PRP precision resistors Nichicon Muse ES audiophile electrolytic capacitors used on the signal path outputGenuine Paper-In-Oil, Sprague Vitamin Q capacitors used on the signal path output (bypasses for the ES caps)Nichicon Muse FG (Fine Gold) audiophile electrolytic capacitors used on the tube cathode bypass Wima MKP10 bypass capacitors used throughout except where Vitamin Qs are presentPanasonic FM power capacitors used throughout Tube LEDs and front plate Power LED for lighting Solid-state Relay-Delay for power-on headphone protectionGenuine Toshiba 2SC2238/2SA968 BJT Transistors in a Diamond Buffer arrangement The PCB measures approximately 6.3" x 6.2" x 1/16". Accessories Included: A 24VAC, 1000ma power supply The Millett Hybrid MAXed Owner's Manual on CD Harbor Freight Digital Multi-meter and Bourn trimmer tool for tube biasing Two (2) pairs of matched tubes!!! Complete information, history, and specifications can be found at diyforums.org: diyforums.org/MAX This is your chance to own a Millett MAX PCB!

Price: 200 USD

Location: Loganville, Georgia

End Time: 2024-10-09T17:00:32.000Z

Shipping Cost: N/A USD