Thanks gentlemen, for your replies,
I will give the subject some more consideration now. Technically, I still not concur with some of the views expressed (but that's me).
1.) Tube amps. Of course tube amps will provide better sound. But the effect is more psychological than anything else (in my view), especially if there is no negative feedback used. Tubes have a softer, squared cut-off point compared to solid-states. The result is the production of even harmonics. Solid state circuits have hard cut-offs and will produce both even and odd harmonics. While even harmonics sound rather pleasant to the human ear, odd harmonics are considered a "true" distortion. That is why most guitarists use tube amps as the over-drive sounds harmonic (Jimi Hendrix would sound awful over a solid-state). Or think of the 12-string guitar. Effectively the same effect. The higher strings are tuned to the 2nd harmonic, i.e. one octave higher.
2.) The isolated loop of the Technics recorders is a self-contradiction. The objective is to achieve a stable tape transport across the heads, i.e. no path deviation, no vibration and flutter. So far okay. In a normal double capstan, the approach is to achieve tension between the capstans. Various ways are known to achieve this. Usually, you allow for slack on the left hand side (for example by using a smoother capstan surface or less pressure of the roller). However, you should always make sure that the right capstan determines, or better, dictates the speed. The winding motors only maintain constant tension, but do not create further slack. The Technics only uses a single capstan but two pinch rollers. If you force a tape loop, this loop disappears quickly. How, if "both" capstans run at exactly the same speed? The answer must be either the re- or the winding motor that forces some slack and helps to avoid loops. My assumption would be an unnecessary level of slack and tape tension to make the system work.
Those were my five cents....
Cheers,
Ulf