Fisher X-101A
Forty watts, twelve inputs, and a chassis full of adjustments - the integrated stereo control amplifier that Fisher billed as the world's most versatile.
Overview
Fisher's own catalog copy for the X-101A leaned hard on superlatives. It called the amp a "Stereo Master Audio Control and Duplex Amplifier" and the world's most versatile control amplifier. The numbers were 40 watts in stereo operation with 75 watts of peak reserve, twelve inputs, eight controls and six chassis adjustments. That is marketing, and collectors learn to discount marketing. But the independent test bench largely backed the claims up, with a few honest caveats.
The design is the classic late-fifties Fisher integrated approach: two 20-watt power amplifiers and a complete stereo preamplifier-control unit in one cabinet. Rated output was 20 watts per channel at 0.7 per cent harmonic distortion and 2 per cent IM distortion, with a 20-20,000 cps frequency response. The same review measured 21 watts on one channel and 23 on the other at 1 per cent harmonic distortion, so the factory numbers were conservative.
The flexibility is the big feature. An eight-position input selector covers 78, LP, RIAA-1, RIAA-2, TAPE, TUNER, AUX-1 and AUX-2. That gives two separate RIAA curves, which mattered when phono equalization standards were still settling. A four-position output selector offers Reverse, Standard, Channel A+B and Channel B+A, and the last two allow two-speaker monophonic operation. The front panel also has separate bass and treble controls per channel, a loudness contour, record-monitor facilities and a rumble filter.
The measured control behavior was solid, not flawless. Channel-to-channel variation of the volume-loudness control was observed at 3 dB, tone controls tracked within 5 dB across their range, and RIAA equalization stayed within 1 dB throughout. The review's wish list was short and specific: a phase-reversing switch in the speaker circuit, and tape-head equalization provisions for the common 3¾ and 7½ ips speeds. Fisher's answer to the latter, effectively, was that nobody buying Fisher gear would be satisfied with 3¾ ips tape anyway. That was a fair point in 1959.
Under the hood, each channel's phase splitter is a cathodyne (split-load) circuit using one half of a 12AX7. It has a 100 k-ohm plate load and a cathode load of an 82 k-ohm fixed resistor plus a 50 k-ohm variable. Output-stage grid resistors are 470 k-ohm. The variable cathode resistor lets a technician trim the drive to the two output tube grids to compensate for mismatched tubes. It is an inexpensive circuit that can balance the amplifier to very low distortion. The catch, documented plainly in the test report, is that the adjustment is chassis-mounted and easy to knock. Moving the control from its optimum to one extreme pushed IM distortion from the rated 2 per cent to as high as 8 per cent. Owners and techs should treat those six chassis adjustments as set-and-verify items, not knobs to fiddle with.
In the fall 1959 Fisher lineup the X-101A was priced at $194.50 and positioned as the heart of the "Stereo Perfectionist II" system package. HiFi-Stereo (March 1960, p.13) called it a moderately-priced but genuinely high-quality stereo control/amplifier that reflected the company's long design experience. It was not the flagship separates, but it was the integrated most buyers could actually justify.
Anyone chasing one today should expect the usual sixty-plus-year-old tube-era problems. Electrolytics and coupling caps are due. The 12AX7 and output tubes need matching to get the best from that phase-splitter trim. The chassis-mounted adjustments should be checked against a distortion analyzer rather than by ear. What you get is a compact, unusually flexible integrated that measures close to its conservative spec sheet and, per Audio's bench work, ranks among the better-engineered Fishers of the period.
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