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The Millett Hybrid Maxed
Technical Highlights
The Millet MAX is the latest refinement in the fine Do It Yourself (DIY) tradition of the Millett Hybrid series
of headphone amplifiers. All Millett Hybrids incorporate a hybrid single-ended vacuum tube gain
stage combined with a solid state output stage. The Millett MAX is no different, but includes features
and refinements that bring this design to a level of performance and convenience heretofore unattained.
The Millett MAX incorporates all of the following features and more:
- The basic Millett Hybrid circuit,
- onboard, STEPS-quality Power Supply,
- onboard, dual Diamond Buffers output stage, and
- onboard, e12 delay circuit (abbreviated for Millett)
Also:
- extruded TO-220 heat sink footprint for power supply
- extruded TO-220 heat sink footprints for all four output transistors
- options for MOSFETs on the output transistor positions
- CCS has been changed to a feedback transistor pair with selectable resistor sizes for different currents and superior tube regulation
- power resistor option for heater circuit, allowing higher voltage supplies without damage to tube heaters
- 16mm minimum cap diameter pads throughout, 18mm for the PS
(Note: This is spacing for 1000uF-1200uF caps and larger. The Panasonic FM's in the photo are 1000uF@50V.)
- 15mm lead spacing for film caps, even larger for cathode bypass films
- signal input pads front and rear, 5mm spacing for terminal blocks
- Noble and Alps adjustable pot positions
- onboard Neutrik output jack pads
- tube LED and panel LED pads included
- PS choice of Schottky rectifier diodes or generic axial diode positions, ceramic snubber caps
- board sized for Hammond 1455T1601 case, center post for stability around tubes
- board dimensions: 6.3" wide x 6.2" (160mm x 157mm), 2oz copper on an 0.062" (1.6mm) FR4 dielectric
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The Power Supply allows the use of a simple, cheap 24VAC walwart supply (750ma minimum recommended), but results in STEPS-quality power. Capacitor pads allow use of very large boutique electrolytics and film caps. The CCS is superior to the old current-limiting diode, resulting in improved tube current regulation for superior performance.
The DB's use only one set of complementary output transistors for each channel, but with the board mounted heat sinks, biasing up to 50ma each and beyond is possible, allowing the transistors to operate within their optimum power range, and lowering distortion for a very clean sound.
Finally, for the ultimate in convenience and protection of your headphones, a small version of Amb's (Ti Kan) e12 delay circuit is used, resulting in 10-15sec power delay and protective cutoff. No need to unplug your phones upon power on or power off.
The Millett Hybrid MAX offers the most integrated board design yet available. After populating the board, all that is needed are a knob, input and power jacks, the enclosure, and a 750-1000ma 24VAC walwart.
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