Not that I am expecting this to be my best performing or sounding tuner... I do not expect it displace my modified Sony XDR-F1HD in that position as my #1 tuner in both weak station pulling power and sonics. So perhaps, I shouldn't have bought this. I am not a nostalga-phile. I try to pursue the best possible sound using the latest technology (such as I can afford), not relax into some 50's or 70's sensibilities.
But I just had to because I've been studying them for nearly 40 years since I first saw one at a new high end stereo business (one of three) in my school age hometown, and I hope it's pretty good sounding tuner, fun to play, and a useful tool because of the oscilloscope.
I believe that business was the store whose cranky and outspoken owner later became famous on the internet, Sunshine Stereo, but during its very brief incarnation in California before moving to Florida.
Anyway, as a pimply faced high school sophmore I wandered into one of the back auditioning rooms, there on a shelf was the 20B. It blew my mind. It may have been playing and sounding elegant as I recall, or just quiet, but sitting there, with scope and blue face and white lights, it was so cool I thought. The owner wandered in, quizzed me about what stations I wanted to listen to, decided I needed his most sensitive tuner, and showed me a Sansui, which kinda looked cheap I thought. He also had an SAE, which he didn't think performed as well as the Sansui for picking up weak stations. But I still lusted for the Marantz.
Later I saw a 10B, and was disappointed that it was not the same tuner. I didn't warm to the appearance of the 10B at first. Now, however, I admit I lust for the 10B more than the 20B. I've bid on 10B's and lost. I hope to get a good 10B eventually, but they are incredibly expensive and unpredictable. They are the most legendary "good sounding" tuner in history, many people have reported fabulous sound from them, though just as often you find negative reviews of them. They appear to need a lot of service only by apprentices of the original designers whose charges are astronomical, though sellers just as often claim their unit has never needed service and still works perfectly. Advertised as never-needing-alignment, the actual history seems to read never-stops-needing-alignment.
Quite a number of people who as Marantz employees or audio salesman lived with both 10B and 20/20B like the 20/20B better. The 20B is said to be a transistorized version of the 10B, based on the same precision toroidal filters (or something very similar), which are often incorrectly described as Butterworth. This tuner uses no ceramic filters which are used ubiquitously in other tuners, but some think are inherently inferior for sonics. Both tuners were designed by the original genius Marantz designers Sid Smith and Dick Sequerra who also went on to design the original Sequerra tuner. It is said to be one of the best sounding tuners, if not one of the best performing tuners (among online reviewers you can find many opinions including these: some think the 10B performs better than anything but sounds worse than the 20B, others think the 20B is better in all ways to 10B as well as being best sounding tuner but not as good performing as others like McIntosh MR78, many tuner fans think both these early Marantz tuners are a joke except in their mythological impact).
The 20B version is different from preceding 20 and 10B in an important way for people who use indoor antennas. It has a dual gate MOSFET RF amplifier with AGC, and changes the first IF transistor from bipolar to FET. That makes it more sensitive. But also, it makes it potentially more subject to overload. There is a switchable attenuator for that. A modern design would use a more modern silicon device (they have gotten extremely good) as RF amplfier for better performance without needing bandaid attenuator. But anyway, unless you have outdoor antenna, the 20B is clearly the one-of-these to get. It should be more sensitive than even the legendary Marantz 10B, which feeds the incoming signal directly to a diode mixer with no RF amplifier.
But despite the boost in sensitivity, this is still not noted for weak station pulling by just about anyone. It is noted for nice sound, interesting built-in scope, and cool looks. A bargain solid state version of the legandary Marantz 10B, and notably more reliable than its predecessor.
Anyway, more fun, I hope, on the way. I bought this one for a relatively high price because it appeared to be in excellent physical and working condition. What happens on ebay is that some mint unit will sell for a huge price, and from then on all the rust bucket barely working units will try to be sold for the same high price. Whatever the primo unit costs extra is often worth paying, but only if it is the primo unit and not some copycat seller. This is about the best looking unit (with numerous high resolution photos) I've ever seen and is described as fully working by the long time audio guru who is selling it.