Mapletree Audio Design
Octal 6A Duplex Stereo Preamplifier Kit

Three preamp topologies in one chassis. Individual channel level controls now replace the single balance control shown.
  • Proven, low-distortion octal tubes (2-12SN7GT, 2-12J5GT, and 2-6R7G). Name-brand NOS types are supplied. Assembled unit can be custom wired for user-supplied 6SN7GT/6J5GT tubes. 
  • Three complete preamp circuits are incorporated: a classic common cathode-cathode follower cascade (CF), a shunt-regulated push-pull (SRPP) circuit, and a passive path. Output and input switching permits any of three sources to be routed to either of the two active preamp circuits or through the passive path which allows use of the selector, volume, and individual channel level controls but with no amplification. A separate record output enables source switching directly to a tape recorder or CD burner. Optionally, the record output can be connected as a second output for bi-amplification or use with a separate headphone amplifier.
  • DC heater supply.
  • All wiring is point-to-point with shielded cable and silver-plated Teflon wire employed in signal paths.
  • Kit includes a punched, painted chassis, bottom cover plate, detachable line cord, all parts, tubes, hardware, wire, solder, fuses,  knobs. and an illustrated 35-page instruction manual. Only a few standard tools and a soldering iron are necessary for construction. High quality components are used throughout: Xicon 1W carbon film resistors, Solen polypropylene film capacitors, Clarostat plastic element level control potentiometers, and Hammond power transformers.
Specifications: Input resistance:  greater than 50K Ohms at 1 kHz. Output resistance:  SRPP: less than 5K Ohms at 1 kHz, CF: less than 700 Ohms at 1 kHz. Voltage gain (100K load): SRPP: 20 dB at 1 kHz, CF: 25 dB at 1 kHz, Passive: 0 dB at 1 kHz. Frequency response, 100K/50pF load): SRPP: 14Hz–35KHz (–0.5 dB), CF: 17Hz–100KHz (–0.5 dB), Passive (power off): dc–110KHz. Noise (100K load):  SRPP/CF: < 0.5 mV,  Passive: < 0.1 mV. 

Email enquiries to Lloyd Peppard at MapletreeAD@aol.com or phone (613) 387-3830