Sony Direct Comparator?

[Micropassatman]

Can anyone(Axel?) help me out here?

I am wondering what the fuss is with Sony's Direct Compare circuit design. I have a Sony ST-S444ESX tuner from the early '80s, and I'd like to know the supposed ins-and-outs of Sony's ES line of tuners.

[axel]

From a 1983 US ES catalog:
"[...] Quartz synthesis tuners were inherently more noisy than the best analog models. So Sony produced one of the most highly acclaimed tuner circuits ever invented. The Direct Comparator.
The Direct Comparator improves audible reception because it functions above the audible frequency range. By making the required PLL comparison directly at higher frequency, the D.C. in tuners like the ST-S555ES cuts through the blanket of noise so prominent in FM reception. Result? A spectacular S/N ratio of 92dB in mono and 86dB in stereo."

From a 1988 US ES catalog:
"The D.C. circuitry provides the accuracy of quartz frequency-synthesis without the commonly associated pre-scaling noise."

The D.C. circuit (CX-778) is located in the front end section of Sony's top tuners ; I believe it still is used today, at least it was until the last "classic" ES tuners got shelved in 1994/95.

Other Sony trickery is outlined on the ST-S707ES post on TVK.
...other manufacturers surely have (had) the same things, tagged with different names :D

[Micropassatman]

Thanks! :thmbsp: