I was thinking of getting into tube for some time I have come accross a dynaco, sca-35 on e-bay will I be disappointed If I'm looking on improving my sound? Right now I have a vintage Sony Str 7045 (that weighs about 35 lbs pushing The original big Advents. Will my sound improve dramadically?
Or should I just wait till I can afford a better tube amp?

The old Dynaco will go for big bucks and require restoration to boot.

The SCA-35 is a cheapo integrated version of the ST-35 and a preamp.

You can do much better either by purchasing a new Dynakit (like the ST-35, a real winner) at http://www.dynakitparts.com/

You can also buy a bare, more modern ST-35 variant at www.diytube.com - I run one and it sounds excellent. Have to source your own parts, chassis, and transformers, tho.

The Dyna may not have enough power for you though, depending on how loud you want to play it. The Large Advents are about 87 Db/1W if I recall correctly - I think a Stereo 70 would be a better match.

First the SCA35 is not an elcheapo amp unless you want to class the ST35 and ST70 as well as the PAS3x in the same category. Same designer, same parts bin and same production technigues. The 35 is an excellent amp and 1 of the better 6bq5 based amps with if any failing its lack of bass emphasis that most person prefer but, the bass is there and in good proportion and balance to the rest of the spectrum.

I've used my unmodded unit with the original Advents and also, have had both a STR6065 and 6045 on them and provided you do not over drive the amp beyond its capabilities, it performs better for classical, jazz and vocals. For rock, watts is king for Advents. My average listening levels for the 35 was not much less than the 6045 and about the same as the 6045.

The key to the 35 as well as any amp of that age is to make sure it is in spec. Not difficult with the amps as it is not a complex design provided you get the version that uses the glass pcb and not the phenolic board based unit. The Phenolic is absorbant and over the years unless in a clean environment get impregnated with pollutants that can affect the sound. Replacement boards are available to cure this.

To kick the 35 up a nothc or 2, simply bypass some of the switching that is not used, change the jackset and bypass the tone controls if you are not using them. Everything is subtractive compared to a ST70 where to get it to sound decent requires extensive circuits modifications including new boards and extensive rebuilding. The SCA35 provided the unit is working just does not need the mods to sound good. The thing about the 35 is that if you get a decent unit you'll get your money out of it later as they are sought after by the tube lovers since it so good.