Sansui 4900Z

A 55-watt-per-channel receiver from Sansui's Z-series, built alongside the 5900Z and 3900Z and documented in the service literature as a shared-platform design.

Overview

The 4900Z sits in the middle of a three-model family. Sansui's service documentation covers the 5900Z, 4900Z, and 3900Z together, and the shared chassis shows in the parts lists. The same power cord, strain relief, AC outlet, 4-pin input terminals for tape and phono, AM bar antenna, ground terminal and pilot lamps turn up across the range. The 4900Z's own identity shows up in the small stuff - its voltage selector board takes a 5A 250V fuse on 100-120V mains and a 2.5A 250V fuse on 220-240V, where the 5900Z takes a 6A and the 3900Z a 4A.

The audio section is rated at 55 watts per channel into 8 ohms, minimum RMS, both channels driven, from 20 to 20,000 Hz, with no more than 0.03% total harmonic distortion. That 0.03% isn't a "typical" number from a marketing sheet. The manual states it as the ceiling at or below rated minimum RMS power output. The intermodulation distortion spec is held to the same 0.03% using the 60 Hz : 7 kHz 4:1 SMPTE method. Damping factor is quoted at 40 into 8 ohms across 20 Hz to 20 kHz with both channels driven.

The phono stage is where the 4900Z earns its keep for anyone still spinning vinyl. Input sensitivity is 2.5 mV into 47 kilohms, with a maximum input capability of 180 mV at 1 kHz before distortion crosses 0.1%. The RIAA curve deviation is held to +0.3 dB / -0.3 dB from 20 Hz to 20 kHz — a genuinely tight tolerance, and one that matters more than the headline power figure when you're listening to a cartridge that tracks lightly. Signal-to-noise for phono is quoted as 50 dB channel separation at 1 kHz, with AUX separation at 60 dB and AUX signal-to-noise at 95 dB. The line-level inputs — TAPE-1, TAPE-2 PLAY, and AUX — all take 150 mV into 47 kilohms, and the tape record outputs deliver 150 mV into 47 kilohms.

Tone controls are the conventional ±10 dB at 50 Hz for bass and ±10 dB at 10 kHz for treble. The high filter rolls off at -3 dB at 5 kHz with a 6 dB/octave slope. The loudness compensation, referenced to the volume control's -30 dB position, adds +8 dB at 50 Hz and +6 dB at 10 kHz. That's a fairly aggressive curve, and owners report it is best used sparingly with modern sources. Audio muting is provided.

The tuner section is fully specified in the same manual. FM tuning covers 88 to 108 MHz with usable sensitivity of 10.8 dBf (1.9 µV) in mono IHF terms, 50 dB quieting sensitivity of 15 dBf in mono and 37 dBf in stereo, and a signal-to-noise ratio of 70 dB at 65 dBf. Stereo separation is quoted at 30 dB at 100 Hz, 40 dB at 1,000 Hz, and 28 dB at 10,000 Hz. Distortion at 65 dBf runs less than 0.3% at 100 Hz, less than 0.15% at 1,000 Hz, and less than 0.4% at 6,000 Hz in mono, with stereo distortion under 0.18% at 1,000 Hz. Image response ratio is 90 dB. The antenna inputs accept both 300 ohms balanced and 75 ohms unbalanced. The AM section tunes 530 to 1,600 kHz with usable sensitivity of 53 dB/m from the bar antenna, selectivity of 30 dB at ±10 kHz, signal-to-noise of 43 dB, distortion under 0.5% at 30% modulation and 80 dB/m, image response of 40 dB at 1,000 kHz, and IF response of 35 dB at 1,000 kHz.

Power consumption is rated at 350 watts maximum, with a rated consumption figure also listed. The chassis measures 485 mm wide, 138 mm tall, and 313 mm deep, roughly 19-1/8 inches by 5-7/16 inches by 12-3/8 inches. Net weight is 9.5 kg (20.9 lbs), and packed weight is 10.7 kg (23.6 lbs). Multi-voltage versions were built for 120, 220, and 240 V markets, with a 120 V (60 Hz) variant for the USA and Canada. The front panel carries a battery case assembly for the memory backup circuit. It shows up in the top-view parts list alongside the power transformer and the two pilot lamps.

Period coverage of the Z-series is thin in the surviving print record. High Fidelity (1981, p.150) listed the line's features in a receiver roundup, noting the patented digitally quartz-locked tuning system, a 15-segment peak-power level LED display, Dolby FM de-emphasis, two phono inputs, two tape inputs, two-system speaker selection, a mike mixing input, switchable FM muting, and LED peak power/signal-strength/center-tune displays. The same listing notes two-way tape dubbing. That feature set is what buyers were comparing against in 1981, and it puts the 4900Z squarely in the digital-tuning transition era — quartz-locked, LED-displayed, but still analog in its output stage and tone controls.

The 4900Z is not the model collectors chase from this lineup. The 5900Z gets the motorized volume control, and that's the one that draws attention. The service manual devotes an entire exploded-view section to it, with a housing cover, indicator film, pulley D-17, tension assembly, film guide, and a motor unit driving a 150kΩ dual variable resistor. The 4900Z and 3900Z share the front-view parts list, and the 4900Z's fuse values sit between the two siblings. The 4900Z offers the same tuner and the same basic amplifier architecture in a less complicated package. It has no motorized volume mechanism, which is, decades later, one of the more failure-prone and difficult-to-service parts of the 5900Z.

The manual's parts lists are unusually helpful. The input terminals are standard 4-pin types shared across tape, phono, and aux. The speaker terminals are the same system A/B blocks used across the range. The AM bar antenna and ground terminal are common parts. The power transformer carries stock number 15001301. The pilot lamps are 8V 150 mA and 8V 300 mA. None of this is exotic. The 4900Z was built from parts Sansui was already using elsewhere in the line.

The 4900Z is a mid-line receiver with a good phono section and a tuner that meets its published numbers. It doesn't have the 5900Z's motorized volume, and it doesn't have the 3900Z's lower price point, but it also doesn't carry the 5900Z's servicing headaches. Look for one with its battery case assembly intact and its original 5A fuse still in the voltage selector board.