"Bryan Dibble" wrote in message
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I own a top-end model ( back then) Zenith 26 " T.V, with A.M & F.M,
Turntable Console

Ca. 60's Zenith audio was pretty grim, as a rule.

and a mid 70's Kenwood Eleven model receiver.

By the mid-70s Kenwood (Trio) solid state receivers were pretty highly
developed.

Why is the tuner portion of the Kenwood so small (and held in high esteem
by some) and the tuner in the Zenith mammoth in comparison?

In the 60's, tuners were based on air-dielectric tuning capacitors which
were physically large. They generally had a goodly number of IF
transformers, which were fairly large taken together. There were very few if
any integrated circuits. For example, a multiplex decoder could be composed
of up to a dozen discrete transistors and diodes, as well as a number of
transformers and coils/

In the mid-late 70's, tuners were based on varacter tuning capacitors which
were tiny diodes. They generally had one or two ceramic or crystal filters
for IF selectivity, which were also generally smaller than IF transformers.
There was heavy use of integrated circuits. A multiplex section could be
reduced to a single tiny integrated circuit, and it would outperform the
larger discrete version.

An anecdote. I had a ca. 1966 Heath AR-15 receiver with a complex FM stereo
decoder with about a dozen transistors and diodes, and at least a half-dozen
coils and transformers. It required constant adjustment. The next generation
of Heath receivers used a single integrated circuit that performed better,
and required vastly fewer associated parts. I retrofitted the
next-generation chip to the AR15, which greatly enhanced its performance and
ease-of-use.

Did technology advance that much in just 5 to 7 years?

It could. There were still some retrograde receivers in production 5-7 years
later.

Or is the older Zenith a better tuner?

I doubt it. As a rule Kenwood (Trio) receivers had better-than-average FM
sections, even in the days of tubes. Sometimes their FM sections
outperformed the amplifier sections, as compared to competitive receivers.
There was one Kenwood tubed receiver that had a great FM stereo section,
but sonically horrific 17 wpc power amps.