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

Curcioaudio.com is one of the better Dynaco ST70 mod sites. Joe, the owner, knows em cold. All the mods are discussed there and he carries all the parts. No "best configuration."

Some of the ST70s iron is great. They really vary as to condition in other ways. Some even say the phenolic boards cause chemical changes in the electronics and change over time and with it the sound - no two are the same.

If you have an older Series 1 the passive componants probabaly could use to be replaced. They weren't expected to go 50 years. There are lots of versions of these amps over the years so advice about moding is tough. What is the number stamped on the output transformer? A-470, maybe.

Lots of discussion in archives at Audioasylum diy tube section on point.

Have fun,
i remain,

www.avahifi.com/70rebuild.htm
This site has a reprinted article that explains in depth exactly how to rebuild/upgrade a Dynaco St-70. Very long, extremely detailed, step-by-step instrucions. I think you will find it very informative. It's on the Van Alstine website. He is currently no longer modding the St-70, but his does offer a complete re-make of the amp with new circuit board design using your old chassis and transformer.

soundvalves.com
avahifi.com

I agree with Sean's good advice. Also,the ST-70 could definitely benefit from power supply upgrades especially in the filter caps, for increased headroom. Doubling the microfarad amount is not uncommon. Frank Van Alstine has been doing excellent mods/rebuilds on these old Dynaco's for years. He would be the first place I would check. He used to offer complete mod packages, in stages, for reasonable money. Probably still does. He's an old timer and he knows what he's doing, especially with Dynaco.I think his company name is Audio by Van Alstine.

Leave it Stock.Only upgrade the passive parts.