Yamaha T-550
A compact AM/FM tuner that paired with Yamaha's A-550 integrated amp. Per the service manual, it packed 33 transistors, 4 ICs, and a 1.7µV FM front end into a 4.5kg chassis.
Overview
The T-550 is a slim AM/FM stereo tuner that Yamaha built as the matching companion to its A-550 integrated amplifier. The service manual gives the footprint as 435 x 92 x 341mm. That's 17-1/8 inches wide and only 3-3/4 inches tall, so it slides under a turntable or stacks on top of an integrated without taking over the shelf. Weight is 4.5kg, or 9 lb 15 oz, which is enough to suggest a real power transformer and not a wall-wart-fed afterthought.
The FM front end is the headline. Yamaha rates usable sensitivity (IHF mono at 98MHz) at 1.7µV into 300Ω, or 0.85µV into 75Ω, both at 9.8dBf. The 50dB quieting sensitivity figures are 3µV mono (14.8dBf) and 40µV stereo (38dBf). That means it pulls in weak stations cleanly but needs a decent signal to go quiet in stereo. Selectivity is where the T-550 earns its keep: 65dB alternate channel selectivity (IHF) and a 90dB IF response ratio keep adjacent-channel bleed well controlled. Image response is 60dB and spurious response 80dB, both at 98MHz. Stereo separation is quoted at 50dB at 1kHz and 45dB across the 50Hz - 10kHz band, which is solid for the class.
Distortion numbers are clean on paper: 0.05% mono at 100Hz and 1kHz, rising to 0.1% at 10kHz. Stereo runs 0.1% at 100Hz, 0.07% at 1kHz, and 0.15% at 10kHz. Frequency response is ±0.3dB from 50Hz to 10kHz, widening to +0.5/−1dB from 30Hz to 15kHz. Signal-to-noise is 84dB mono and 80dB stereo at 65dBf, so hiss isn't the limiting factor unless you're chasing a marginal signal. Capture ratio is 1.5dB, and AM suppression is 60dB.
The AM section is less ambitious but perfectly serviceable: 525 to 1,605kHz tuning, 15µV usable sensitivity (IHF), 27dB alternate channel selectivity at 1,000kHz ±9kHz, 52dB signal-to-noise, and 0.3% distortion. Image response is 40dB and spurious response 50dB, both at 1,000kHz. Output level is 500mV at 1.6kΩ for FM at 100% modulation and 170mV at 1.6kΩ for AM at 30% modulation. The REC CAL output is a 333Hz tone corresponding to 50% FM modulation, specified at 250mV at 1.6kΩ. The service manual's calibration procedure says it should land within −10±3dBm. HI-Fi-Stereo-Buyers (November 1980, p.55) noted that the review sample's record calibration output measured −4dB below 100% modulation rather than the rated −6dB.
Inside, the T-550 carries 33 transistors, 4 ICs, 1 FET, 10 diodes, 1 zener diode, 10 LEDs, and 3 ceramic filters. Power consumption is just 9W. The service manual lists four regional power supply variants: 120V/60Hz for US and Canadian models; 110-130V/220-240V at 50/60Hz for the general model; 220V/50Hz for the North European model; and 240V/50Hz for British and Australian models. The front panel carries a tuning knob, a combined LED tuning indicator and dial pointer, a signal quality indicator, an FM stereo indicator, a function switch, an FM muting switch, a REC CAL switch, and the power switch.
Period reception was positive but matter-of-fact. HI-Fi-Stereo-Buyers (November 1980, p.55) described the T-550 as an AM/FM stereo tuner companion to the A-550 amplifier at $190. It called out the stereo beacon, the LED tuning indicator combined with the dial pointer, the six-step LED signal-strength display, and the "equal green LED brilliance." The same review noted AM reception as "notably" good, which is rare praise for an AM section in a budget tuner. At $190, the T-550 undercut much of the competition without giving up the essentials: decent sensitivity, respectable selectivity, and a clean REC CAL output for tape deck calibration.
The T-550 is not a DX machine. The 1.5dB capture ratio and 65dB selectivity are good but not exceptional, and the 40µV stereo quieting threshold means weak stereo signals will be noisy. The real value is as a matching piece: if you own an A-550, the T-550 completes the stack visually and functionally. The REC CAL output is useful for calibrating cassette decks, and the six-step LED signal display is more informative than a simple center-tune meter. Common failure points aren't documented in the available material, but the 9W power consumption and modest 4.5kg weight suggest a straightforward, serviceable design. The service manual is thorough, with full alignment procedures for both FM and AM sections, which makes the T-550 a reasonable restoration candidate for someone who wants a period-correct Yamaha tuner without the complexity or cost of the T-2 or T-80.
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