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Eh!!
TX-11(1984)
The first TX-11 is FM-only.
The FM section has a fairly ordinary, good RF section with wide and narrow IF bandwidths.
What makes the TX-11 special is the extremely clever patented stereo manipulation circuits that turn weak or distorted broadcasts into very listenable signals. For most people who are using only a crappy indoor antenna, this tuner will outdo most other tuners because of these circuits.
Carver's crazy-name for these circuits is Asymmetrical Charge-Coupled Detector, which has nothing to do with how it works, but sold more tuners to those without FCC 1st-Class radiotelephone licenses.
See its ad in the Carver section of the October, 1985 issue of Audio magazine.
TX-11a
The TX-11a has the FM section of the TX-11, and adds a very special AM Stereo section.
The AM section is quite unlike anything else: it's wideband and has a Motorola C-QUAM stereo decoder, not that anyone is broadcasting in AM Stereo anymore.
The AM section has full low-frequency response; it's not rolled-off as it is on all other consumer tuners. In Stereo, it cancels, not filters, the 25 Hz pilot.
On AM, it has a very clever and patented noise blanker to improve listening, and most importantly, has superb high-frequency response not found on other consumer AM tuners.
Since it has such great AM response, it also has a patented 10 kHz notch to remove beats.
On AM, as well as FM, it has two IF bandwidths. Even at Narrow, the AM section is far superior to any other consumer AM tuner. In all honesty, all consumer AM tuners sound like you're listening through a paper-towel roller because consumer tuners roll-off the high and low audio frequencies. This Carver tuner does not, and sounds like a professional AM broadcast monitor.
On AM, it also picks up far more and better long-range broadcasts than other AM/FM tuners, and on decent signals, sounds just like what's going over the air, and not like a honky little radio like every other AM section. Listen, and you'll be astounded: the AM section of this Carver sounds better then AM HD radio because it has none of the digital data compression artifacts that make HD radio sound swimmy and wishy-washy.
It remembers station presets a long time when not plugged in. Mine easily recalled everything in January 2015 after being unplugged and stored since June 2014; or seven months.
TX-11b
The TX-11b is the same as the TX-11a, simply removing the 300 Ω FM antenna input and making some minor circuit updates. According to folklore, Carver simply needed to find another Japanese contract manufacturer, and since he had to take the design elsewhere, made a few small tweaks.