Sony ST-4950

Name: Sony st-4950
Brand: Sony

A tuner that earns its keep on the antenna, not the spec sheet. It has a few things to teach the collector who can look past the missing Dolby badge.

Overview

The ST-4950 is a sophisticated, high-sensitivity FM stereo/AM tuner. Sony's own documentation says it was built for "discriminating audiophiles" who cared more about signal integrity than badge engineering. The front end runs a MOS FET stage feeding solid-state IF filters and an IC IF amplifier. Sony claimed this combination delivered selectivity and sensitivity without distortion even in strong-signal areas, plus lower noise and better interference rejection. A tuner that folds in the presence of a strong local transmitter ends up in the closet. The ST-4950 was explicitly engineered not to do that.

The multiplex section is where the ST-4950 does its quietest work. Sony specified a Phase Locked Loop FM multiplex demodulator IC, and the company's manual promises the greatest stereo separation and the lowest possible distortion from that arrangement. Period coverage in High-Fidelity (February 1976, p.112) likewise credited the PLL MPX section with excellent stereo separation and low distortion. Tuning is handled by a new-type CG variable condenser, with an LED dial indicator marking stations sharply and precisely. The AM section gets its own attention: a newly developed IF filter for better interference rejection, and an improved AGC circuit in the RF block that widens input dynamic range while keeping distortion down.

Almost nobody else in this class bothered with a dedicated SIGNAL MULTIPATH meter. Multipath is the reflected, phase-smeared signal that ruins stereo reception in cities and near hills. Normally you fight it blind. Sony put a meter on the front panel for it. Press the MULTIPATH switch and the meter stops showing signal strength and starts showing the magnitude of the multipath component. Rotate the antenna for a minimum reading, then recheck that signal strength is still sufficient for low-noise reception. The manual suggests the whole procedure takes a few seconds. It is the most useful diagnostic tool on the tuner, and it is the reason an ST-4950 in a difficult reception location can outperform tuners with better paper specs.

There's also a discriminator output jack, provided for adaptors that might be required for discrete four-channel FM transmissions. Most owners almost certainly never used it. The unit accepts both 300-ohm twin lead and 75-ohm coaxial antenna connections. The manual is unusually firm about installation: keep leads short, avoid long horizontal runs, keep the antenna lead away from mains cables and at least three meters from TVs and fluorescent lights.

The ST-4950 sits in an awkward but interesting spot in Sony's lineup: sophisticated enough to satisfy a serious listener, modest enough that it never commanded flagship prices, and honest enough in its construction that forty-plus years later it's still worth the bench time. It isn't the tuner you buy to impress a visitor. It's the tuner you buy because you actually listen to the radio, and you'd like to hear what's actually being broadcast.