THIS HAS BEEN EDITED
So, I went through the pile and the only real nice amp I found was a Sansui AU 317 II. Worth the trouble?
I had two Alpha AU-317's, but like Rat Fink, I had to get very brutal because stuff was just piling up, so both of them went out to the recycle plant. One of them was part way into being restored — that is being recapped and replacing some transistors and so on. The Mark II model seems to be very similar to the ones that I had, so perhaps I can comment.
Yes, these are nice amps. Their fame did not glow as much as the models that produced twice the power, but that should be of no concern to anyone with relatively efficient speakers. Anyway, 50-60 Watts is lots of output. What matters is how accurate the sound is, and these amps have a good reputation. Like all the Sansui amps, these were very good sounding units — very natural and non-distorting, even at full tilt boogey. All Sansui amps have good power transformers.
There is one drawback with
some old Sansui, and you will not know until you have opened it up. For awhile, Japanese manufacturers were obsessive about "pegging" or "staking" board capacitors. That is to say, they were
glued to the board. This was to ensure nothing moved in shipment. And, BTW restorers generally do not reglue the new caps. The problem is/was that Sansui used a glue that decades later has caused a chemical interaction with the phenolic on the board and the aluminum base of the cap. Sansui maniacs (and there are some on AK Sansui forum) take this in stride. Getting the old caps out can be difficult, and you end up cleaning the board. Of course, the Mark II may not have used glue, or they may have used another type of glue.
Now another thing. If you replace the filter caps (a very excellent idea) ... they really
do need to be reglued on this unit. Ideally they should have been clamped and/or perhaps mounted separately from the main board. Anyway, they are not, and I don't believe that they are physically stable enough without a dab of epoxy on one side just to peg them. The other caps you can just solder in the usual way.
For some years, I had a big alpha AU-717 Extra in my main rig. A great amp!!