Company History

David Hafler and his friend Herb Keroes started a Philadelphia, PA based company called Acrosound in 1950, dedicated to building and selling audio-quality output transformers. Herb's mother invested a substantial amount of money in the company, which apparently didn't return much of a profit. As part of the marketing of the transformers, and concurrent with Hafler's own interests in audio, they developed and extended the Blumlein "Ultralinear" circuit, using taps from the output transformer to feed signal back into the output stage screen grid circuitry. Numerous homebrew as well as commercial hi-fi amplifiers from the early '50s were based on Acrosound transformers. Hafler was interested in selling entire amplifiers as build-it-yourself kits, a somewhat novel approach in the early '50s. The average hi-fi enthusiast generally started with a schematic, chose an output transformer (which determined the power of the final amplifier), selected parts and tubes accordingly, then hand-crafted his unique component on a homemade chassis. Further, Hafler's idea was to supply preassembled, tested circuit boards which only needed to be connected to the transformers, controls and power supply to produce a working unit. Even the Heath and Knight units of their day generally required the purchaser to assemble and test the PC boards themselves, a time-consuming task.

In 1954 Herb and Dave went their separate ways (allegedly due to differences of opinion over kit production and marketing). During a visit to the New York-based Brociner Electronics (owned by Victor Brociner, whose influence in audio design was also far-reaching) Hafler met up with Ed Laurent who had designed a novel single-tube driver circuit for a power amplifier. More or less together, they founded the Dyna Company with the intention of not only producing transformers, but high-quality audio circuitry using them. Soon after incorporation in October 1955 at 617 N. 41st St in Philadelphia, Dynaco announced the Mk. II 50-watt amplifier. Available as a kit or preassembled, it sold for several years, into the 1960s, superseded only by the soon-to-be-classic Mk. III 60-watt unit. Hafler wrote an article for Radio-Electronics Magazine in 1955 delineating the design of a high-power version of the "Williamson" amplifier using Ultralinear circuitry and the new output transformers. This amplifier offered a slightly different circuit topology from the Mk. II and Mk. III units soon to appear in Dynaco's line, but showed that the Ultralinear idea was applicable to many amplifiers. Shortly thereafter, Dynaco moved to 3912 Powelton Ave., where they remained for several years. Interestingly, the building was the former site of a chocolate factory, and the old walk-in refrigerator served as a well-isolated listening room!

Demand for the PAM-1, Mk. II and Mk. III was sufficient for Hafler to develop new offerings; Laurent collaborated with editor par excellence Bob Tucker to produce the legendary Stereo 70 while Hafler was on a business trip. Soon Dynaco had a handful of high-quality amplifiers and preamplifiers, including a new series of stereo gear, and their first FM tuner -- the FM-1, originally a Stewart Hegeman design "distilled" by Laurent -- in 1961. A stereo adapter designed by Sid Lidz (at a fraction of the cost of other available adapters, fitting into a specially reserved slot in the FM-1 chassis) and later a fully integrated stereo tuner soon followed. Although Dyna switched to buying their output transformers from a local Philadelphia company, and finally a Japanese source, all were still manufactured to the design specifications developed by Hafler. Ed Laurent was the chief engineer during these years, and he contributed to the design of virtually all the vacuum tube circuitry. He and Bob Tucker followed Hafler's lead in producing simple, reliable, easy to manufacture and assemble electronics and the best manuals in the industry.

In the mid-1960s, Hafler's company released its first solid-state equipment; the PAT-4 and Stereo 120 pair (again the product of Laurent's expertise in circuit design) made a hit and were well-reviewed by the audio magazines. Not as collectible today as their tube brethren, these units are still remarkable for their sound quality 35 years later. During this period, Dynaco moved from their Powelton Ave. location to larger facilities at 3060 W. Jefferson St. in Philadelphia. Also introduced during this era were the first commercial products to generate passive matrix recovery of ambient signals from conventional stereo recordings; the DynaquadTM system found its way into the QD-1 Quadaptor and the SCA-80Q "4-dimensional" integrated amplifier. Late in the 1960s, Dynaco dropped another blockbuster in the form of the A-25 bookshelf loudspeaker, designed by SEAS Fabrikker in Denmark and imported by Dynaco. Praised as few other speakers in hi-fi history, the A-25 went on to sell over a million units and spawn a line of up- and down-scaled systems to match the range of electronics offered by Dyna.

In the 1970s, Dynaco made history again and again with a new series of solid-state units which continued the trend of maximum quality for the money. Ed Laurent moved over into management of the loudspeaker product line, handing solid state design over to a new generation of engineers that he hired in turn. Led by chief engineer Wade Burns, designers Erno Borbely, Jim Bongiorno, Harry Klaus, Hans Frank, Richard Pley, and others produced a stunning sequence of respectable equipment. Their FM-5 tuner, PAT-5 preamp and Stereo 400 power amplifier drew rave reviews from the critics, who mercilessly compared the new units to equipment several times their price and offered only minor criticisms. Dynaco's tube units continued to sell well into the 1970s, bolstered by Laurent's last design -- the monoblock Mk. VI. In fact, the Stereo 70 sold virtually without a break right up until 1990 (more about this later). Audio Research Corporation offered retrofit kits for the Stereo 70 as part of their 1970s line, and many many third-party modifications have sprung up around the infinitely versatile Dyna circuitry. Dynaco's exemplary second- and third-generation solid state gear, such as the Stereo 150, QSA-300, ST-410, SE-10 equalizer and SCA-50, kept the mid-line alive even as the awesome Stereo 416 (Wade Burns' 'maximized' ST-400 with more output transistors, a better power supply and meters than any similarly priced competing amplifier) revived Dyna's reputation as the audio leaders in 1977.

In (1973?), Dynaco had moved from their Philadelphia home to nearby Blackwood, NJ where they remained until their demise. Employees cited often-dangerous conditions in the surrounding Jefferson St. neigborhood and frequent vandalism as strong incentives for the move. It was much safer and more conducive to operating a business in the new location, and Dynaco flourished. Plans were laid for a follow-on series of advanced loudspeakers and another generation of solid-state gear, and the innovation continued.

Dynaco became a wholly-owned subsidiary of Tyco, Inc. in 1969. David Hafler remained with the company a few years longer, but left in 1974 to join Ortofon, manufacturer and importer of high-end phono cartridges. In 1977, Hafler founded the Hafler Company, continuing the tradition of high quality but inexpensive kits and assembled hi-fi gear. Former Dynaco employees Bob Tucker and Harry Klaus contributed their authorial and technical expertise to Hafler's cause at his new company. In the mid-1980s, Hafler developed the straight-wire differential test (SWDT) for audio amplifiers, a typically straightforward and effective tool for evaluating linearity -- proving that the man who founded Dynaco was still at the cutting edge. Though the Hafler company is still a major player in high-end solid state equipment for audio and professional sound systems, David Hafler lost control of the organization which bears his name in a power struggle and has since retired.

Tyco tried to revitalize the Dynaco name in the face of competition from foreign hi-fi manufacturers by encouraging the design of an all-new solid state product line and holding on-site repair/upgrade clinics at Dynaco's strongest retailers. The new product line suffered a tragic setback when the prototypes were stolen at the Atlanta Hi-Fi Show in the mid 70s, a loss that has not been recovered or adequately explained in 25 years. Due to subsequent cash flow problems, the new components (featuring such equipment as the 2510 preamplifier, 2501 tuner, 2530 integrated amplifier and 2521 power amp) were never produced. Dynaco employees of that era remember Tyco's acquisition for an overall improvement in work environment (due partially to the move) and marketing, with many new product ideas coming to fruition. In spite of Tyco's efforts, and record sales of their sturdy equipment line, Dynaco's profits began to slide and their once-preeminent position among american hi-fi manufacturers was in danger. Rumors surfaced concerning the possible sale of Dynaco, and sure enough, the Dynaco holdings were sold to ESS Inc. in 1979.

ESS seemed puzzled as to what to do with the acquisition. Anecdotal reports from the ESS era indicate that their management of Dynaco's assets was less than successful. Dynaco, the company, closed its doors in 1980. When ESS decided to unload their inventory, the Dynaco brand, parts and kits were picked up by Stereo Cost Cutters/Sound Values Inc. in Columbus OH. SCC/SV revived the FM-5, AF-6, ST-150, SCA-50, SE-10, and ST410 kits without redesign or parts substitution. When original parts were exhausted, some of the units ceased to be available; others were repackaged with new metalwork, cases, etc. and re-issued. The Black Box 410 and Black Box Stereo 150 were examples of the latter, which stretched availability of those units into the 1980s; a few BB150 units were still available in 1990, when the author purchased his.

Realizing that Dynaco tube units were becoming even more popular than the solid-state equipment, SCC/SV brought back the Mk. IV, PAS-3X and Stereo 70, which sold well until the last of the NOS Dynaco transformers, boards and metalwork were exhausted in the early 1990s. They even managed to produce a small run of Mk. VI amps before their parts store ran out. At this point, with the original Dynaco stock virtually gone, SCC/SV ended 14 years of Dynaco sales and parts support and turned their efforts toward designing new tube and solid-state gear for the enthusiasts. They still produce high-quality yet relatively inexpensive new components today under the name Sound Valves, though they are unable to provide parts or tech assistance for Dynaco equipment (for obvious reasons!).

In the late 1970s, Dynaco released a short-lived set of new loudspeakers developed under Ed Laurent's supervision before he departed to join SEAS Corporation. The "Phase III" speakers were highly respected, but their introduction was apparently too late to make any strong impression on the audio industry. After Dynaco closed, another company (apparently the Canadian subsidiary, though the details are not clear; obviously someone still owned the Dyna branding for loudspeakers at that time) released the Dynaco A-150, A-250, and A-350 speakers which were manufactured in Canton, MA. Reaction to these units was not favorable, and they disappeared from the review magazines in the mid-1980s.

In the early 1990s, the Dynaco brand was picked up by Pan Orient Corporation (now Panor Corporation), which started selling original design equipment under the Dynaco brand; they offered the PAS-3 series II, PAS-4, CD player, and Stereo 80 tube power amp. Panor still owns the Dynaco brand name, but any direct connection with the company founded by David Hafler has apparently ended for good. On the other hand, I have recently received information from Panor, indicating that they have re-opened their web site at, and that the Singapore web site is in no way affiliated with the company known as Panor Corporation or with the Dynaco brand. Apparently the Dynaco brand will still be around for some time, and hopefully still be associated with high-quality low-cost stereo equipment (more products are promised in the near future). I haven't had time to check out any of the new Panor equipment yet, though. More news here as it is available.

On a positive note, it is remarkable that many former Dynaco employees (from the Hafler era) are still in touch with one another; the fellowship and shared vision of the company extended into their private lives, and many of them are still using their 1960s-vintage equipment on a daily basis, as is the author of this web site.

So what is the current status of Dynaco and support for the equipment? None of the original principals are involved in support for Dyna equipment any more. There are a number of audio companies who sell upgrade kits and tech assistance for the tube equipment, but almost no one who still supports the solid-state amplifiers. Part of the reason for my providing this web site is to make a rallying point for Dyna enthusiasts, in hope that we can pool our resources and make as much tech info available as possible, develop a network of shared schematics/troubleshooting info, etc. So write me at the address below if you have any info to share; I will be building and updating a set of links to assist Dyna enthusiasts in keeping their equipment running well into the 21st century!

I would like to thank Wade Burns, James Elliott, John Ferranti, Doug Hercus, Ed Laurent, Richard Pley and Joseph Sparacio, former Dynaco employees, for contributing to the accuracy of this historical document and correcting my timeline of Dynaco's latter days. Also thanks to Kevin Devaney and Dov Sassoon for recent info as regards the current state of Panor's holdings. Any mistakes I have made interpreting their comments, or conclusions I have erroneously drawn, are my responsibility and not theirs. As I receive further info from them and others, I will continue to improve the history page and add data to the component pages. It is clear from their passionate interest in accuracy that Dynaco's employees cared greatly about the company and each other, and it has been my privilege to hear their comments and share information from their own experiences at Dynaco with the world community.

RIP: Harry Klaus, who contributed to many fine Dynaco products; Sid Lidz, designer of RF and power components; Bob Tucker, author of most of Dynaco's first-rate manuals; Bill Phillips, Dynaco's "golden ear" and customer service manager; and Joe Sparacio, technician. They will be missed.

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