The Starving Student Millett Hybrid PCB is the latest refinement of Pete Millett's Do It Yourself (DIY) Starving Student headphone amplifier. Just like the original Starving Student design, the Starving Student Millett Hybrid incorporates a hybrid single-ended vacuum tube gain stage combined with a solid state output stage. Forums user Dsavitsk has taken the original circuit and applied it in an ingeneous way to a simple PCB with a clever case design. There were two main issues solved in applying this PCB, with many benefits, not the least of which is retaining the original's inexpensive cost to build. First, the MOSFET output stage develops a tremendous amount of heat. Therefore, heat sinking requirements are paramount. Second, while the Starving Student follows the Millett Hybrid family tradition of using low-voltage power, in the case of the SSMH this "low" voltage is 48VDC. That's enough to a little uncomfortable if contacted in the right conditions. So, totally enclosing all the voltage components was another feature developed in the design.

The Starving Student Millett Hybrid uses a pair of MOSFETs as the output stage, coupling these to the tube gain stage with interstage coupling caps. The MOSFETs themselves are connected so that they are Class A current biased directly from the tube heaters. This results in a non-adjustable 150ma current bias through the MOSFETs, virtually guaranteeing total Class A operation with almost any headphone on the market today, including some older, esoteric types such as Orthodynamics. The PCB and case are designed to dissipate this heat directly through the case and a pair of inexpensive, yet high-heat rejection, TO-3 style heat sinks. While exact temperatures can vary quite a bit, depending on the individual build, this combination is sufficient for the amp to withstand constant running over a period of literally dozens of hours.

Please note also that in keeping with the "Starving Student" theme, there is no relay-delay on the SSMH as there is on the Millet MAX/MiniMAX family of amps. There is measureable DC at the headphone jack before the tubes have warmed up. We strongly encourage you to disconnect your headphones from the SSMH upon start-up and prior to turning it off. When this simple procedure is followed, the SSMH should give you and your headphones many hours of listening pleasure.

The Starving Student Millett Hybrid PCB incorporates all of the following features and more: The basic Starving Student circuit (2 x 19J6 tubes, IRF510 MOSFETs), options for input resistors to control gain, options for cathode bypass capacitors, options for output film bypass capacitors, and options for grid-leak resistors. Note that all of these features improve the sound quality over the original SSMH circuit. Also: extra-large pads to support 18mm-dia capacitors, all resistor pads except for R16/R17 sized to use 1/4W or 1/2W resistors, board-mounted Neutrik headphone jack, board-mounted, inexpensive Alpha volume pot with grounding wire pad, 5mm pitch terminal blocks for convenience in connecting signal, power, and switch wiring, grounded center post position for stability around tube sockets, and board-mounted tube sockets.

(assembled SSMH PCB amps) (PCB production version)

And: sized for the inexpensive Hammond 1455N1201 enclosure (custom machined case available!!) board dimensions: 3.87" wide x 3.14" (98mm wide x 80mm) , 2oz copper on an 0.062" (1.6mm) FR4 dielectric

Like the original Starving Student, the Power Supply is an inexpensive, VoIP (Voice over Internet Protocol) telephone power supply - the Cisco PSA18U-480C, rated for 48VDC at 0.38A from a 120-240VAC input. These supplies are plentiful and can be found almost anywhere that VoIP technology is sold. In addition, the power supplies are widely available in surplus outlets and on ebay (search for "Cisco PSA18U"). This supply is more than adequate for the Starving Student PCB using all options, including the tube LED's.

Join us in constructing the the Starving Student Millett Hybrid, PCB-version. We believe you will find that it offers an extraordinary value in DIY-headphone amplifiers.