The Super Pas looks good, and it would be a good candidate for a Super Pas 3 upgrade, but the upgrade would be the same as upgrading the stock Dyna Pas. If you are looking for a chassis to upgrade you may want to see if you can find a cheap stock Dyna Pas preamp that looks good.
Just as a further caution/comment on old Dyna stuff - don't forget that some of this stuff is getting downright ancient. I have taken the task, recently, of restoring a PAS 3 and ST70 for my father. Like many people, I have various bits of Dyna equipment hanging around in various states of disrepair, and of course like most engineers, I am absurdly cheap and like working on things. My father's stuff was built in the early- mid-60s and has had virtually no maintenance since then. It was nicely assembled in the first place, but on opening it up was a very scary thing. The power supply choke in the ST70 was literally burned black including the steel frame, with a huge black spot around it where it had outgassed and deposited the results on the baseplate. Stuff was dripping out of the capacitors, and of course the driver board was burned black under the driver tubes. Despite all this, and the fact that the bias was unsettable, it still worked and was not totally objectionable. The preamp was in even worse shape - the chassis was rusted through the plating in many places, and the interconnects were literally held in place by rust. The old original knobs, cast from zinc and the plated, had what appeared to be the pox. In attempting to remove the tubes from the phono board, I brushed against the solid wiring - and it just broke off. I wasn't pulling on it, just barely touched it, and it broke off at both ends. Other than one of the driver tubes in the ST70, both units had *all the original tubes*. And it's run, on average, probably an hour or two a day since 1964.
Of course, you can still get all the parts to build an ST70 from scratch, and half-a-dozen different brand-new kits. When I started looking at restoring the ST70, I started adding up what I needed to restore it to original with the exception of the cut/jump to use 6gh8a tubes (vice the $25 a pop and soon to be unavailable 7199). Yes, I could buy it all - for a grand total exceeding $600. That includes scavenging other units that I have in my storage unit. The chassis and transformers are in good shape (after cleaning up the alarming brown residue from 45 years of cigarette smoke exposure - wow) so I figured I would REALLY fix it and go for a U70 kit for around $500 total. Either a stock ST70 for $600 or a far superior product for a few evenings work and $500. A no brainer.
The PAS is a another issue - it was just a basket case to restore, and parts are not that easy to get, particularly chassis parts. Once again scavenging was helpful, but it was to the point of a Super PAS kit + complete disassembly of the chassis so I could find someone to clean up and re-plate it, take knobs in decent shape from other units, and an absurd amount of time and money. Normally I would prefer doing it myself to having anyone else (including Frank and company) do it for me, and I am very adept at this sort of thing, but this was ridiculous. So I got the "trick" unit from Frank instead.
If it weren't for the nostalgia aspect and the fact that my father would be upset with me for "spending too much money", it would be far more cost-effective to just by a AVA integrated amp new and move on with my life. I owe him on the hi-fi front anyway - I released the magic smoke from his Heathkit AA-100 when I was about 14 when I was, uh, "improving" it.
My point it, beware what you are getting yourself into with some of this older stuff, particularly from eBay or other sources you can't inspect beforehand. ALL of these things are getting very very old and are very likely to be either unmaintained basket cases, or "modified" with who-knows-what changes and (from what I have seen) mostly atrocious worksmanship. My fathers was the former, and I suspect that many eBay units are the latter. Assume that you are only buying the chassis and maybe some working transformers, and that the chassis may be a basket case in and of itself.
I started out trying to rework my father's working unit to original condition and making sure it wasn't going to burn down the house. I ended up having to buy a complete aftermarket unit and $500 worth of parts with 20-30 hours of free labor. He will end up with a MUCH better than stock product that will certainly be safe to use. But it was a lot more difficult and costly than even I suspected. Be advised - buying current-production sensibly-priced products will be a whole lot easier and likely yield better results than trying to restore the average 40+ year-old Dyna stuff of random provenance.
Brett
