dynaco st 70 what tubes to replace first

Dav65mus, you've more or less ended up in the same place I have with my ST70.

The one difference being I prefer the JJ E34L to their KT77. You give up a bit of low frequency performance, which isn't the strong suit of the ST70 anyway, but the midrange and treble open up a noticeable (in a glorious, but not harsh way)amount more.

For the record, I have a bunch of highly regarded amplifiers, and while the ST70 doesn't outclass them in terms of power or low end, not one of them can match its overall tone. To me, that's why it's the amp I enjoy the most. For all of the shortcomings people love to chirp about, I shake my head at how far things have not come since the mid - 1950s.

1959, actually. One of the most important components in the building of a good sounding tube amp is the output transformer(if you're going to use one). The originals in the ST-70 were pretty darn good. With upgraded RCAs/speaker terminals/PC/chassis wire, more capacitance in the power supply, better coupling caps and resistors; the old jewels can really sing, even with the original driver board. That's not to mention the fun the modding provides.

You might want to look at a qusd of NOS Tesla EL 34 if you can find them.

All tubes asap.