While in theory, tube tuners suffer from greater tendency toward front end overload by powerful stations in urban environments, RF interference, and inferior multipath rejection of "ghost" signals than transistor designs, I haven't heard any practical demonstrations of these shortcomings with the 310C. I'm located about 3 miles from downtown Boston, and while some stations do occupy a broader area on the 310Cs' dial than they do on my Magnum Dynalab 101 tuner, in late night logging tests using the Magnum "Silver Ribbon" dipole antenna, the 310 brought in 39 stations to the Magnums' 45. Not too bad for outmoded technology.
On days of poor reception, the 310C is not appreciably worse than the Magnum. WBUR, an NPR station in Boston affiliated with Boston University occasionally produces background hum or whistles with the Scott 350 in multiplex stereo mode, but the 310C is as silent as the Magnum. If you do a great deal of off the air taping, as I do, you will find that the 310C is the equal of almost any modern tuner, this can't be said for many older tube designs. On the Scott 350, for instance, there is no way to insure that during the course of a two hour live symphony broadcast it will maintain good clean reception for the entire length of the concert.
Early 310s (up through the 310D) are quite inexpensive on the used market. The problem is that the multiplex adapter, model 335, needed for stereo reception is not as readily available, and is usually more expensive than the tuners themselves. Other manufacturers' MPX adapters can be used with the 310s. I've tried the Fisher unit, and the results were virtually identical in terms of performance, it did sound differently, however. Other adapters like those made by Eico or Bogan may not produce as satisfactory results, as some of their early units were not up to the quality of the Fisher and Scott units.
The 310E was made for a limited time in 1963. It is my favorite Scott tuner. I like it so much, I sold my Magnum Dynalab Ft101, in favor of the 310E in my main system. It brought in almost as many stations as the Dynalab (43 stations to 45 for the Dynalab), and did it with more musical sound. It is as drift-free as the 310C or the Dynalab, and best of all, it was cheap - $75. The 310E is more neutral than the 310C. Gone is the mid-bass hump, and excess warmth. The 310E has a more extended top end than the 310C. Its' top end extension is the equal of the Magnum Dynalab FT 101. The 310E has a slightly more spacious soundstage than the 310C, and more apparent depth than the Dynalab. While the Dynalab is certainly not raspy or hard, like many solid-state tuners (the Sony STJ-75 comes to mind), it sounds somewhat raspy compared to the 310E.
The only negative about the 310E is its looks. It resembles, not so much the middle period Scott tuners, like the 350, as the early solid-state models, like the 312. Gone are the curved corners and brass knobs. Instead we have plastic knobs with metal caps that come unglued and fall off, similar to the knobs the famous Fisher 500 series receivers. It is boxy, and squat, and even a well-finished wooden case won't help it much. Yup, it looks ugly, but sounds beautiful.
The 310E makes a very good argument for never spending more than $100 for a tube tuner. While I haven't done a mano-a-manos with Scott 4310s or Marantz 10Bs, I can't see why, other than collectors' mania, anyone would put out the big bucks for these pieces. The 310E blows away a stock Macintosh MR 71 tube tuner. The Scott receives more channels, with higher definition, more high-end extension, and better harmonic balance. The Mac sounds dark and harmonically constricted in comparison.
When I asked Daniel Von Recklinghausen, Scotts' chief design engineer during the period of "classic" tube equipment, which Scott tuner he liked the best, he said, without hesitation, the 310E.
The 350 was the first tuner to have a built in multiplex adapter. Its front panel is simplicity itself, containing the by now famous circular tuning dial, AGC Multiplex-mono switch, Stereo noise filter switch, level control knob, on-off selector knob for mono, stereo, and stereo with sub channel filter, and tuning meter. It is finished in the traditional golden bronze brushed aluminum.
The 350 has good sensitivity (2.5uv IHFM method), and 35db selectivity. When compared to a Scott 310C, it logged in as many stations, but only the strong local stations were of equal sonic quality to the 310C. With some stations there is a tendency towards whistling and humming if the station is not tuned in precisely. Luckily the 350 has an output level control, because at full output the 350 is capable of overloading some preamp line inputs. Like the 310C, the 350 as the ability to soften the hard edges, and warm up the metallic midranges of Rock stations. It is a euphonic unit, but its effect is subtle enough not to engulf stations with good sonics in a honey dipped glaze.