Mods for DYNA ST-70, What do you think??

There's a guy that has done MAJOR re-design of the Dyna PAS-2 and PAS-3 using very advanced computer simulation and a lot of know how. His name is Norman Koren and he's had more than a few articles published in various tube / tweaker mags.

I intend to modify my Dyna pre using his basic suggestions once i get the time. Don't know if he's done anything with the amps, but you can try checking his website. It would at least give you an idea as to what is involved in modifying / upgrading a unit of that nature.

AVA ( Audio by Van Alstine ) may be another good source for parts and schematics but i don't think that his ideas are near as progressive. Sean
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http://www.normankoren.com/Audio/

I think soundvalves.com points out that even the stock version has some easily correctable mistakes that to do just a parts upgrade would be a bit of a shame. So at the very least/minimum go their route, along with the better parts. Now if you want to take it further others have presented those options too.

If you do nothing else get rid of the selineum rectifier. Replace it with a diode. These things blow up and take other stuff with them and when(not if) they blow they emitt a toxic cloud into your room!

I did the soundvalves mod ($99 many years ago), with great results....more detail, etc. I also replaced the selenium rectifier, beefed up the power supply with more caps, and parallelled all electrolytics with small value Wonder Caps (you would use MIT caps today).

I have modified several ST-70s over the years and the only stock parts I keep are the chassis, transformers, choke, and bias pots. Everything else (RCAs, quadcap, binding posts, etc.) should be replaced with quality parts. I have replaced the 7199 front end with a 12AX7 front end that Jim Aud of Purist Audio came up with several years ago. Considering it's hard to find good 7199s anymore the 12AX7 front end is the way to go and is sonically superior.