Munich HIGH END Show Report 2017
Dynaco ST-70 Series 3 Stereo Integrated Tube Amplifier @ HIGH END 2017
High End Society Munich Germany
HIGH END 2017 Show Report By Steven R. Rochlin

  Dynaco (a division of Radial Engineering Ltd.) presented their re-launch of a legendary tube amplifier, the ST-70 Series 3 tube amplifier, that was first shown worldwide during Enjoy the Music.com's HIGH END Munich event last year. Dynaco's ST-70 Series 3 stereo tube amplifier produces 35 Watts per channel stereo and switchable between both 4 and 8 Ohm outputs.

Using Class-A push-pull stereo topography, versions of this amplifier in the past have been characterized as a robust, with a reliable design of exceptional value. The ST-70 Series 3 builds upon the proven design philosophies of the original David Hafler-designed Stereo 70, with contemporary design techniques resulting in exceptional performance improvements that meet the requirements of modern audiophiles. Dynaco engineers have made extensive use of high-quality parts that were unavailable at the time of the original design including precision metal-film resistors, poly-composition capacitors and miniaturized high-capacity power supply electrolytic capacitors.

In addition, many of the newer parts are also built to tighter specifications than the originals. For instance, the PCB is constructed of military-grade, double-sided epoxy fiberglass PC material. In compliance with modern practices, the speaker binding posts have been updated, and a heavy-duty three-pin detachable grounded power cord is provided. Signal ground is the same as electrical ground and chassis, and all signal connectors are gold-plated. The latest rendition has seen a substantially overhauled power supply from the original version, employing a larger dual-primary power transformer with improved line regulation, increased filter capacitance, and a solid-state rectifier that results in a much more articulate response.

The resulting bottom end is a dramatic improvement over the original Stereo 70's low-end response. This is augmented with a three-position high-pass filter switch to allow listeners to tailor the low-end response of the amplifier to their personal tastes. Using a redesigned front end of the Series 3 amplifier, the company replaces the 'obsolete' 7199 pentode signal tubes from the original Stereo 70 with more commonly-used 12AU7 dual-triode tubes as part of a configuration that harkens back to the classic Williamson amplifier - this in itself has a long-storied history in the audiophile community. The output stage and EL34/6CA7 output tubes retain the same elements as the original Stereo 70 yet with the new design, the bias adjustment for the output tubes can be individually set using a front-panel recessed trimmer for each tube.

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Getting back to the Dynaco ST-70, after a warm up period (and with no input signal present), the bias is easily set by matching the brightness of the front-panel LEDs. Tremendous effort was applied to improving upon the original output transformers in an effort to increase damping and tighten up the low frequency response . A rear-panel switch allows the listener to select between 4 and 8 Ohm speaker loads. The feedback location is also configured by this switch, and the gain is adjusted accordingly. This results in an improved transient response when compared to older Stereo 70 implementations. Learn more about the Dynaco ST-70 Series 3 stereo integrated tube amplifier within our HIGH END 2016 show report. Pricing is TBA and delivery is anticipated to begin summer 2017.

They had the ST-70 setup in an open, corner-ish display with Polk floorstanding speakers and it did sound quite good, and powerful! While not an ideal location, was impressed by the sheer power and underlining bass being joined by excellent midrange and smooth upper frequencies. Bravo and look forward to hearing the ST-70 is a more formal setup.

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