Chris Keller Dynaco ST-70

The Dynaco ST-70 is the quintessential tube amplifier. In many ways it is the very definition of the tube amp, and if one were to see a photo in Webster’s it would make sense that this was the one. By some counts there are 350,000 or more of these amps out there, making this the largest production tube amplifier of all time. A new design when Eisenhower was President (1959), this is a long proven platform and a sound signature that a wide array of people can identify with. In some ways it's the baseline.

I’ve been eyeing ST-70 amps for a long time, but its been on the back burner, as I figured that in reality I just don't have a setup that wants or needs 35 watts of power. Well, as it turns out those misgivings were ill placed; the ST-70 runs an efficient single driver to its limits and it sounds great!

Backing up a bit, this is a Chris Keller rebuilt ST-70 using the VTA driver board with 3 12AU7 tubes, so a departure from the original design. This one has the good transformers and has been rebuilt from the ground up. The result is a super solid amplifier that performs flawlessly, and with such a great wide and richly engaging sound signature. Man, that big voice is there with the rich undertones that the vintage stuff does so well, but this one has a modern sound on top of all of that strata. This ST-70 is a modern sounding amp, and it kicks ass. It images, it has power in reserve and it sounds like a tube amp should, quietly calm and relaxed, but ready to pounce at will.

I will say this, the ST-70 is an engaging, well rounded sound that is full where it should be and slippery light on its feet where the program material requires that. It's a remarkably good sounding amplifier, and is certainly the height of the “Vintage” sound signature for me so far. The Dyankit 70 betters the Scott and Sherwood amps I’ve owned in pure fidelity at least. If I walked into a room where this was playing under a curtain and out of sight I might think this is a single ended 2A3 amplifier. And that’s one of the really surprising, and frankly quite enlightening things about owning this ST-70; the power doesn't over-power the playback. It is solid, but nimble as hell. The ST-70 is a classic, and like the 300B and 45, in my opinion it should be on every tube audiophile’s list to experience at some point. Highly recommended if you can find a properly updated unit.

A great looking classic ST-70. Chris Keller knows what he is doing with these amps!

The VTA board uses 3 12AU7 tubes, a good and inexpensive choice that offers a wide variety of possible sounds.

Rear inputs were one of the things I'd been looking for in a rebuilt ST-70. I've never been fond of running the interconnects into the front of an amplifier.

Volume control by Audio Music's amazing TVC.