specs and features
specifications and features :
original fairchild 670 circuit -
original tube regulated high voltage power supply
original AGC - lat/vert MS matrixring , dual mono .
original time constant values.
original signal amplifier
original control amplifier
the only alterations to the circuit are dual mono dc heater supplies to protect the 1200$ in tubes. and 1200$ in audio transformers .
also providing a hum less low noise sound stage .
a power supply voltage measurement port on the power supply to monitor the critical voltages of the units operation window
via a decade network of 909k resistors (voltage meter bridge available on request).
high voltage metering and balance metering selectors are achieved through high voltage relays switched by
grayhill mil spec rotary selectors .
cathode balance uses 10 turn precision bourns wire wound potentiometers .
this is a vast improvement from the original 1 turn cathode balance pots, achieving a balance of the most stubborn 6386 tubes.
heater supplies for left and right channel are separate (dual mono) linear type with whisper quiet maglev fans for cooling.
the high voltage regulator heater supply is also dc regulated and separate.
all heaters use high efficiency micrel LDO regulators and schottky diodes .
all with highly filtered input and output rails and the highest quality components.
the tube bias power supply is same as the original design , however the +/- 10% bias choke may be substituted
with a high accuracy negative voltage regulator . (protecting the performance and longevity of the 6386 cathode bias)
the control amplifier bias is unregulated like the original to match the line voltage of the HV supply during
fluctuations in line voltage .
all signal connections are at the front of the pcb ( no middle of the board connections)
all power connections and audio connections are at the rear of the pcb .
xlr connections are done via a shielded cable from the main pcb to neutrik xlr sockets .
all front panel controls are pcb mounted for ease of construction and reliability and safety.
fused heaters and double fused mains (one 5amp fuse in the IEC socket one 4 amp fuse on the front panel
before the power switch)