INTRODUCTION
Much has been written about these amplifiers ranging from their wonderful sound, to restoration needs, to their transformer failures. I’ve long been familiar with the W-5, with my first contact over 40 years ago when I was gifted one by a family member who built it in 1958. It included the larger Peerless 16458 output transformer, and after an initial checkup, still proved to run acceptably well at the time. Having only one however, it’s been in storage ever since. I always remembered it though as a piece where Heath really started stepping out on its own. A few years ago, I then acquired a second one from AKer Audiodon (RIP) that also employs the larger output transformer, creating a matched pair. It too has good transformers, and both are in decent physical condition, but certain aspects of the design have always left me lukewarm about these amplifiers, so it sat too.
The W-5 was released to great fanfare in 1955, being on exhibit at the Heath booth at the IRE Convention of that year, complete with its (unknown) designer in attendance. It’s design topology follows the classic W series designs that preceded it, but also continued with some uniquely Heath developed features that had previously been tested on some of their earlier amplifiers. This included the “Tweeter Saver” feature (output Zobel network) that started with the W-3AM, and an input impedance isolation network (starting with the W-4 series) — both being measures taken to keep their later Williamson offerings stable, versus the notable instability of their prior amplifiers. To this, Heath then put a real polish on the W-5. A new output transformer was developed for the W-5 (Peerless 16309, later upgraded to the larger 16458 transformer in 1957), and this time the transformer included convenient leads for each output tap, eliminating the terminal re-strapping required to change the output impedance in previous models with Peerless units. The chassis was refined with their new gold and black look, that for the first time also included a top cover, and even (long overdue) chassis ventilation holes. The output stage had additional stopper resistors added to accommodate the upgrade to premium KT66 output tubes, a new and simpler method was devised to balance them, and the front end was now populated with miniature tubes sporting tube covers. In the audio circuits, coupling capacitor values were altered again and other component values adjusted, while in the power supply, the rectifier tube was upgraded to a higher voltage 5R4GY type, and series connected filter capacitors now appeared in the first three filter sections. B+ voltages were elevated, power output increased, and for the first time, a very detailed presentation was made of the amplifier’s complete performance, covering no less than 7 pages in the Assembly Manual. For Heathkit then, the W-5 was their tour de force designed to draw a line in the sand regarding the company’s standing in the high fidelity industry. So, polished this amplifier was. Exact production numbers aren’t known, but judging by the number of examples generally available, it was certainly another Heath success story.
Recently however, I became interested in how Peerless transformers might have improved over time throughout their role in the Williamson story, since it was one of their transformers that was specified for use in Sarser and Sprinkle’s “Musician’s Amplifier”, which originally introduced the Williamson amplifier to this country. That amplifier solidified the fabled Peerless S-265Q output transformer as the gold standard for true Williamson amplifiers — an off the shelf production piece available in 1949 that is still revered even today. Since Heath was largely following S&S’s work with the Williamson, they also commissioned Peerless to produce the output transformers for their original WA-1, W-2M, and now W-5M amplifiers.
The period from 1949 to1957 however (when the 16458 was introduced) represented a time of great change and development in the design and production of output transformers. To see how that period might have brought improvements to the Peerless line then, it occurred to me that with my W-2 amplifiers I had already evaluated and modified earlier:
http://audiokarma.org/forums/index.php?threads/regilding-the-gilded-lily-heaths-w-2m.767851/
and the W-5 amplifiers I had in storage, I already had a 1952 benchmark and a 1957 bookend to look at, needing only a real S-265Q to complete the pair of bookends for the period, and an original W-5 16309 transformer to fill in the gap. Enter AKer Zackthedog, who not only had a spare authentic Peerless S-265Q, but also a Heyboer copy of that transformer, and an original 16309 as well that he kindly lent me for my investigation. It didn’t appear that any measured performance evaluation had previously been published on the W-5 (amateur or professional), so I finally had the motivation needed to get my W-5s out of storage and make them operational. As with the W-2s, their stock performance could then be fully analyzed and evaluated, along with that of the transformers Zack provided, to see if any real performance improvement had been achieved. Any opportunities for improving the amplifier itself could also be observed and potential solutions developed along the way.
As it turns out, the investigation showed that there were some surprising aspects of this amplifier’s design — hidden within it — that centers specifically around the Peerless transformers it uses. They were surprising enough to suggest that the W-5 — while no doubt a good amplifier as originally offered — has the potential to be much better.
As with my previous work on Heath’s W-2, W-3 series, and W-4AM amplifiers, this article is hardly meant to be critical of Heath’s efforts with the W-5 for the sake of being critical. 1955 was in the thick of some pretty heady times in the world of high fidelity design, with history showing even some of the best manufacturers of that day struggling mightily to maintain the best from their designs amid all the changes and new standards being established. This, in conjunction with the importance of marketing their product’s features for maximum appeal to the audio enthusiast of that day, made for some pretty intense needle threading to turn an audio buck. Therefore, there is little to be gained by arm chair quarterbacking today, the design decisions Heath made so long ago, since all the influencing factors have all but evaporated now. Those factors however have left opportunities today that the benefit of nearly 70 years of hindsight and modern approaches can provide better answers for, which can significantly improve the W-5 — both audibly and measurably.
The opportunities presented are divided into two basic groups: The first group is aimed at basic dependability issues only, and can be performed with minimal changes to the original design. The second group promotes maximum dependability, and is for those wanting to achieve maximum performance from the amplifier.
Much has been written about these amplifiers ranging from their wonderful sound, to restoration needs, to their transformer failures. I’ve long been familiar with the W-5, with my first contact over 40 years ago when I was gifted one by a family member who built it in 1958. It included the larger Peerless 16458 output transformer, and after an initial checkup, still proved to run acceptably well at the time. Having only one however, it’s been in storage ever since. I always remembered it though as a piece where Heath really started stepping out on its own. A few years ago, I then acquired a second one from AKer Audiodon (RIP) that also employs the larger output transformer, creating a matched pair. It too has good transformers, and both are in decent physical condition, but certain aspects of the design have always left me lukewarm about these amplifiers, so it sat too.
The W-5 was released to great fanfare in 1955, being on exhibit at the Heath booth at the IRE Convention of that year, complete with its (unknown) designer in attendance. It’s design topology follows the classic W series designs that preceded it, but also continued with some uniquely Heath developed features that had previously been tested on some of their earlier amplifiers. This included the “Tweeter Saver” feature (output Zobel network) that started with the W-3AM, and an input impedance isolation network (starting with the W-4 series) — both being measures taken to keep their later Williamson offerings stable, versus the notable instability of their prior amplifiers. To this, Heath then put a real polish on the W-5. A new output transformer was developed for the W-5 (Peerless 16309, later upgraded to the larger 16458 transformer in 1957), and this time the transformer included convenient leads for each output tap, eliminating the terminal re-strapping required to change the output impedance in previous models with Peerless units. The chassis was refined with their new gold and black look, that for the first time also included a top cover, and even (long overdue) chassis ventilation holes. The output stage had additional stopper resistors added to accommodate the upgrade to premium KT66 output tubes, a new and simpler method was devised to balance them, and the front end was now populated with miniature tubes sporting tube covers. In the audio circuits, coupling capacitor values were altered again and other component values adjusted, while in the power supply, the rectifier tube was upgraded to a higher voltage 5R4GY type, and series connected filter capacitors now appeared in the first three filter sections. B+ voltages were elevated, power output increased, and for the first time, a very detailed presentation was made of the amplifier’s complete performance, covering no less than 7 pages in the Assembly Manual. For Heathkit then, the W-5 was their tour de force designed to draw a line in the sand regarding the company’s standing in the high fidelity industry. So, polished this amplifier was. Exact production numbers aren’t known, but judging by the number of examples generally available, it was certainly another Heath success story.
Recently however, I became interested in how Peerless transformers might have improved over time throughout their role in the Williamson story, since it was one of their transformers that was specified for use in Sarser and Sprinkle’s “Musician’s Amplifier”, which originally introduced the Williamson amplifier to this country. That amplifier solidified the fabled Peerless S-265Q output transformer as the gold standard for true Williamson amplifiers — an off the shelf production piece available in 1949 that is still revered even today. Since Heath was largely following S&S’s work with the Williamson, they also commissioned Peerless to produce the output transformers for their original WA-1, W-2M, and now W-5M amplifiers.
The period from 1949 to1957 however (when the 16458 was introduced) represented a time of great change and development in the design and production of output transformers. To see how that period might have brought improvements to the Peerless line then, it occurred to me that with my W-2 amplifiers I had already evaluated and modified earlier:
http://audiokarma.org/forums/index.php?threads/regilding-the-gilded-lily-heaths-w-2m.767851/
and the W-5 amplifiers I had in storage, I already had a 1952 benchmark and a 1957 bookend to look at, needing only a real S-265Q to complete the pair of bookends for the period, and an original W-5 16309 transformer to fill in the gap. Enter AKer Zackthedog, who not only had a spare authentic Peerless S-265Q, but also a Heyboer copy of that transformer, and an original 16309 as well that he kindly lent me for my investigation. It didn’t appear that any measured performance evaluation had previously been published on the W-5 (amateur or professional), so I finally had the motivation needed to get my W-5s out of storage and make them operational. As with the W-2s, their stock performance could then be fully analyzed and evaluated, along with that of the transformers Zack provided, to see if any real performance improvement had been achieved. Any opportunities for improving the amplifier itself could also be observed and potential solutions developed along the way.
As it turns out, the investigation showed that there were some surprising aspects of this amplifier’s design — hidden within it — that centers specifically around the Peerless transformers it uses. They were surprising enough to suggest that the W-5 — while no doubt a good amplifier as originally offered — has the potential to be much better.
As with my previous work on Heath’s W-2, W-3 series, and W-4AM amplifiers, this article is hardly meant to be critical of Heath’s efforts with the W-5 for the sake of being critical. 1955 was in the thick of some pretty heady times in the world of high fidelity design, with history showing even some of the best manufacturers of that day struggling mightily to maintain the best from their designs amid all the changes and new standards being established. This, in conjunction with the importance of marketing their product’s features for maximum appeal to the audio enthusiast of that day, made for some pretty intense needle threading to turn an audio buck. Therefore, there is little to be gained by arm chair quarterbacking today, the design decisions Heath made so long ago, since all the influencing factors have all but evaporated now. Those factors however have left opportunities today that the benefit of nearly 70 years of hindsight and modern approaches can provide better answers for, which can significantly improve the W-5 — both audibly and measurably.
The opportunities presented are divided into two basic groups: The first group is aimed at basic dependability issues only, and can be performed with minimal changes to the original design. The second group promotes maximum dependability, and is for those wanting to achieve maximum performance from the amplifier.
