We have previously reviewed the parallels between the post-WW II hot rod culture
and the American Hi-Fi industry. Both were kick-started by returning vets, putting their service training into practice; both were fueled by the tremendous material bounty provided by war surplus. Many hot rods and "Flats" racers (speed-record competitors on the salt flats of Nevada and California) were cobbled together from cannibalized wing-tanks and the aluminum skin of scrapped warplanes, painful to contemplate though that may be. Similarly, more than one electronics manufacturer designed their circuits around surplus electronic components.
If you look at back issues of Hot Rod magazine from the late '40's and early '50's, you'll see a progression of familiar names as amateur racers became manufacturers: Edelbrock, Winfield, Crane, Crower. As years go by, you'll see how employees of those companies left to launch their own ventures. The result was an industry.
Likewise, in the American Hi-Fi world, tech-trained servicemen returned home, became involved in radio or audio at an amateur level, and then started a company. Those companies spawned many other companies, and bingo, an industry resulted. Our focus here is upon the part played in that process by the Dyna Company, commonly known as Dynaco.
In Part 1 of our Dynaco history
, we discussed Dynaco founder David Hafler's former company Acrosound, which primarily made transformers. When Hafler and Ed Laurent started Dynaco in order to market amplifiers in both kit- and factory-assembled forms, quality, self-made transformers were a key ingredient of the company's products. It could be said that they were THE key ingredient, as the high performance of the transformers used in the Mk. III and ST-70 made Dyna's products stand out from amps offered by other companies. Indeed, as we'll see, Dynaco amps were often so heavily modified that little remained of the original Dyna piece other than the transformers.
We may think of "tweaking" or "hot-rodding" as a recent phenomenon, but upgrading the performance of factory offerings goes back to the dawn of the radio industry (and the car industry, for that matter). J. Gordon Holt devoted the entire Winter, 1966 issue of Stereophile to a DIY Stereo 70 modification article by Ed Dell, entitled "The Beast" . Dell was an ordained Episcopal minister who published the Audio Amateur and Speaker Builder magazines, today melded into Audio Xpress
Dell constructed a massive regulated power supply for the ST-70, built on a second chassis which connected to the original amp by an umbilical connection. Performance of "The Beast" was undoubtedly a major improvement over the stock Stereo 70, but Holt, oddly, never reported subjective impressions of the unit. Subscribers of the irregularly-published magazine appeared less than thrilled by the loss of an entire issue to a construction project; letters in subsequent issues were irate, and Stereophile stayed away from DIY for 20 years. (John Atkinson later published a piece by Corey Greenberg on a DIY passive preamp, and two DIY speaker designs from Dick Olsher; otherwise, Stereophile's focus has been on factory-made gear.)
The inherent strengths of the PAS-2 and PAS-3, Mk. III, and Stereo 70 have made them popular subjects for rebuilds and modifications, long after new pieces stopped appearing from the factory. With over 300,000 ST-70s produced (according to Wikipedia
), there are still many around to this day. Examples of tweaked Dynaco amps often appear on Audiogon, such as this beautiful modified Stereo 70
.For those wanting to work from scratch, schematics of all the Dynaco tube amps and preamps are available on the Triode Electronics
website; they also offer replacement parts, upgrades and complete new kits.
Probably the best-known of the Dyna-tweakers is Frank Van Alstine, who has offered mods, kits and completely new Dyna-based units for close to 40 years now. Audio by Van Alstine
offers an "Ultimate 70" tube amp which clearly shows its Stereo 70 roots.
One of the companies which got its start thanks to Dynaco, is Audio Research. Starting back in the days of Bill Johnson's retail shop, before they became well-known for their SP-2 and SP-3 (sound familiar?) and Dual-75 and Dual-76, ARC offered complete rebuilds of Dynaco Stereo 70s, totally replacing the circuitry and utilizing only the chassis and transformers from the original amp, as shown on the Audio Research Database
website . ARC even sold rebuild-kits,but eventually turned the sale of kits over to Old Colony Sound Labs, run by none other than Ed Dell ( almost going full circle back to Dell's "Beast"). An article on the ARC ST-70 mod also appeared in Dell's Audio Amateur magazine in the late '70's.
Even today there are so many modifications available for Dynaco products that there's no way we can list them all. Our apologies to those we've missed; undoubtedly there are a number of companies like Curcio Audio Engineering
, who have offered Dyna parts and mods for decades.
Our next installment of the Dynaco history will cover the solid-state products and the continuing influence of the brand. For further reading, we suggest you look at the extensive archive of Dyna-related posts from the Audiogon Forums