Pioneer's BEST Preamplifier EVER! Pioneer SPEC 1 (my favorite preamp!)

Launched two years after the Exclusive C3 in Japan as a would-be Exclusive, the 1975 C-77 became for the export markets the famed SPEC-1 preamplifier in 1977.
If the circuits are partly similar, the execution isn't and Pioneer kept a fair distance between the C-77 and the Exclusive C3.
The C-77 cost 120,000¥, the Exclusive C3 380,000¥ so... smaller transformer, a more standard 4-gang attenuator, no luxurious wood enclosure either and the addition of a non-audiophile MIC mixing function.
Circuit-wise, the SPEC-1 is an all-Class A SEPP design : phono, flat amp, tone controls and output, three stages every time.
The flat amp has a PNP differential amplifier with 3-stage DC class-A SEPP circuit, with a ±48V split power supply and 100% DC negative feedback in the first-stage for DC stability.
Other ±48V supplies feed input and output buffers to raise input and lower output impedances.
The all-important phono stage is also fed by two ±48V supplies to ensure a high overload level of 500mV at 1Khz.
The phono 2 input has a distinct smaller 4-gang input level to adjust its sensitivity between 2,5mV and 10mV (or 0dB to -12dB) ; its level up to -6dB is adjusted by and NFb loop and by the output attenuator until -12dB.
The volume attenuator is a 4x 50kOhm / 22-steps 4-gang ALPS (as usual) with an added three-position muting switch for 0dB, -15dB and -30dB input levels.
A relay mutes the output when the SPEC-1 is switched on or off.
Tone controls are of the NF type, allowing between their MAIN and SUB section 5929 tone altering possibilities.
Inside are all low-noise PNP/NPN transistors, micron-tolerance circuits and resistors.
Added to the C-77 for its SPEC-1 export version is a set of one speaker input and two speaker outputs, in addition to the two pre-out terminals.
The headphones output are derived from those added terminals which feed the power-amplifier(s) signals back to the SPEC-1.
On the C-77, the output selector is simply labeled "output" and there are no added speaker terminals.
The C-77 sold somewhat poorly in Japan and vanished rapidly, the SPEC-1 sold very well elsewhere, remaining available in Germany as late as 1980 with stocks lasting quite probably even longer than that.
Pioneer was then at the A-9 and the Communication Series but demand was still there for old-fashioned silver.
The Spec-1 has differential amplifier circuitry incorporated in the equalization and tone control amplifiers.
This is complemented by a dual positive and negative power supply system for all amplifier sections, which provides improved DC balance and stability, while eliminating click noises due to switching.
An electronic muting circuit, employing a reed relay, blocks surge noise associated with power switch operation.

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