ST-70 modifications

K&K Audio has a mod package for the ST-70. It converts the amp to 10 watts triode. Might be worth looking into.

I have experience with both the Curcio mod and more recently with the Alan Kimmel kit that Ron Welborn sells. I've been extremely impressed with the Kimmel constant current design, but it really changes the character of the amp. If you like the romantic quality of the stock ST-70, I'd recommend the Triode kit. You'll get much better bass control & stability, and much better parts quality than the original Dyna parts.

The Kimmel design makes the ST-70 sound like a modern amp, much more extended highs and tight bass. It is still rich in the mid-range, but a lot less lush sounding than the original. Mine has Tung-Sol 6u8a's and black plate RCA's in the driver board, with Gold Lion KT-77's and Mullard rectifier. Frankly it sounds fantastic with appropriate efficient speakers. But it is NOT a kit for the unskilled, although I hear the latest version has better instructions. You need to be able to read schematics and should know something about tube amp construction. If I do another one, I would definitely do the Kimmel again, but I'm a masochist... YMMV.

One more kit you might look at, and that is the driver board offered by Mapletree Audio Designs. The MAD board is said to be very nice sounding, but I have not heard it myself, altho I have a MAD octal tube preamp I built which I like a lot.

there's a pretty good dyna board on AA you should check out. Lots of folks have trodden these paths. If you need help, just ask.

HTH

The K&K Audio mods for the ST-70,sound amazingly good. I had one in my system for a couple weeks.

Last year I built a bone stock ST70 kit from dynakits.com I also bought a VTA board along with triode kit to convert it to after getting a baseline on the stock amplifier.

I own a lot of highly regarded tube amplifiers, and with the modern resistors and caps and decent tubes (RCA 7199 & JJ E34L), the stock amplifier is so captivating, I've never felt the needs to implement the upgrades I've already paid for.

For what it's worth, I'd recommend rebuilding the driver board with modern parts and see how you feel at that point.

Just to add a little more detail to my request, I am not an experienced DIY'er. I have made interconnects and refoamed speakers but that is about it. I am pretty comfortable with my ability to solder and follow instructions and take my time on projects, but I have never built or rehabbed an amp or preamp. So along with the quality of sound, I need something relatively simple to install.....I would prefer a completed board as opposed to a blank board with all the parts and instructions. I think I need to replace the main driver board and the quad cap. Thanks again for your input.