AA Acoustics AA34 integrated amplifier

The Dynaco ST70 reborn

Integrated amplifiers
AA Acoustics AA34
AA Acoustics AA34 integrated amplifier

I’m a big fan of the one-line summary. Here’s the one for the AA Acoustics AA34: It’s a Dynaco ST70 with an input selector, a volume control and a remote. That’s it. Job done. The show’s over, almost no need to read the rest of the review.

Remarkable as it might seem to our American counterparts, some outside of the US might not have heard of the Dynaco ST70, however. Back in the mid-1950s, David Hafler and Ed Laurent’s Dyna Company started producing ultralinear tube amp designs based on the Williamson amplifier. Then in 1959, the company released its Stereo 70 power amplifier, a 2x 35W EL34 based stereo chassis built with good transformers either as a completed product or a full kit. The amplifier proved to be the biggest hit in tube history, with more than 350,000 units sold over the years. Although Dynaco is long gone, the ST-70 is still one of the most popular seed circuits for today’s tube amplifiers. It’s still one of the amplifiers to beat, even today and is loved by our American cousins.

In fact, it could be argued that the high-end audio industry sprung out of the ST-70, because before there was an Audio Research, the late William Zane Johnson built his early reputation on modding the ST70.

The AA34 is the first of a new line of products from AA Acoustics. Which is another way of saying it’s a UK-specced version of the Dynaco ST70 made by the Chinese company that makes Consonance. AA Acoustics (the UK company) used to be known as Alium Audio. It’s virtually identical to the ST70, with a valve roll-out of a pair of ECF 82s in the input stage (the original used the 7199, a different pin-out variant that is rare today), a single 5Z4P as a rectifier and two pairs of EL34s. AA Acoustics suggests this delivers 40W per channel (with four and eight ohm terminals) at less than one per cent distortion and low overall feedback from two feedback loops. It’s self-biasing too.

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