Mapletree Audio Design Prototypes

Do it Yourself (DIY) Goodies/Engineering Prototypes
The designs shown here are some of the one-off prototypes designed and built at Mapletree Audio Design for presonal use, demonstration, or just for fun. Perhaps some of you DIYers will find ideas, useful information, and inspiration here. If you have any questions or comments, contact Lloyd Peppard.
*6AS7G Monoblocs* click on image for larger view	6AS7G dual low-mu triodes in Class A push-pull operation 6W per channel Push-pull driver transformer with parallel feed 6F8G, 77 voltage amplifier tubes 6DA5 cathode ray indicator tubes for output power display Separate power supply chassis No electrolytics in power supply Tube regulated B+ for voltage amplifier stages Schematic Another view of power supply Power supply chassis wiring Amplifier chassis wiring
*"Cadbury" Mk I Headphone Amplifier* click on images for larger view	6EM7/6EA7 dual triodes for each channel 600 mV output at 1 kHz into 32 Ohms (110 mW) 65 mV input sensitivity 80 mV noise View chassis
*"Cadbury" Mk II Headphone Amplifier* click image for larger view	5751 driving two 12B4As as cathode followers parafeed output transformer circuit drives 32 Ohm headphones line output for use as line preamp volume and blend controls same circuit to be used in new MAD Ear 4 kit SOLD
*6CK4 Stereo Power Amplifier* click on images for larger views	6CK4 triodes in push-pull class AB₁ Fixed bias dc and ac balance plus bias adjustments Bias current meter 12SJ7GT input voltage amplifier 12SN7GT long-tailed phase splitter Schematic Power Supply Schematic
*807 Monoblocs* click on image for larger view	• 807s in class AB₁ triode mode • ac and dc balance plus bias adjustments • 6SJ7/EF37A input voltage amplifier • 6SN7GT long-tailed phase splitter • 6GX8 indicator tube level display Schematic Under-chassis view
*Line-Level Preamplifier*	• 6FQ7s in mu stage circuit topology • Individual output level controls • "Magic eye-tube" output level indicator • DC heater supply Schematic
*Electronic Crossover*	• 6 dB/octave, 500 Hz, for bi-amping with two full-range speaker systems • 12BH7A cathode followers on all outputs • Flat output for feeding another processor • "Magic eye-tube" level indicator • Regulated DC heater supply Schematic
*7-Band Equalizer*	• Gyrator-based filters using 5751s • Bypass switch • Auto or manual B+ delay/standby • Nine 5751s and one 12AT7 • Regulated DC heater supply for each channel • SOLD Schematic
*Nuvistor Phono Preamplifier*	• Two 6CW4 and one 7586 nuvistor per channel • Passive RIAA equalization • Three separate regulated dc heater supplies • Selectable input capacitance • Switchable record output • Output level control • SOLD
*"Octal 12" Stereo Line-Level Preamplifier*	• Three selectable circuit topologies: cathode-follower, SRPP, and mu stage • 12SN7GT, 12J5GT and 6R7G tubes • DC heater supply • Tube rectified/regulated B+ supply with standby switch • Individual output level controls • SOLD
If you have any questions or comments, please email Lloyd Peppard at peppardl@post.queensu.ca.

Do it Yourself (DIY) Goodies/Engineering Prototypes