PL Similar to Dynaco - Is The Transformer The Real Basis For WOPL Rebuilds?

[Bob Boyer]

And now for a discussion question from the peanut gallery for all you White Oak builders/users/designers. After skimming and reading several of these rebuild threads - including the latest from Hexis 22 - and seeing the slightly different approaches taken, I've almost come to the conclusion that, like old Dynaco gear, the only real magic in an old Phase Linear is the transformer. Given the seemingly obsessive approach to re-engineering everything about a Phase Linear from Joe and others and the incredible results everyone obtains from using these products, this feels a lot like the Dynaco tube gear redesigns that do so much by ignoring everything Dynaco except the transformers and basic circuit design. Or is there more there as a starting point?

Thoughts? Thanks!

 

[marcok]

The secret of Dynaco is the output transformer e not the power tranformer .
Output tranformers must be linear and must have no saturation .
At present only McIntosh and a Swedish company ( Lundhal ) are able to build
very good output transformer and probably a Japanese company (EL )
Other manufacturers always say : We too are able to !
Diffiicult to demonstrate .
Regarding power transformers are " only " iron and copper " IMHO ,of course !
In other words designing a power transformer is easier .
Ciao
Marco
P.S. If my memory serves me PL 700 / 400 have a special circuit ( patented ) to recovery
energy . Probably the "PL secret " . Joe surely knows !

 

[laatsch55]

Joe has done everything earthly possible to retain the Phase Linear sound . The basic circuit design is the same, with improvements in the implementation and component selection.

 

[marcok]

https://patents.google.com/patent/US3727148A/en
Ciao
Marco

 

[Gepetto]

https://patents.google.com/patent/US3727148A/en
Ciao
Marco

Hi Marco
That is just the short circuit protection circuit that they used in the early days. They abandoned this in later generations of their amplifiers.

Has nothing to do with recovering energy, just protecting against accidental output shorting.

 

[marcok]

Joe , my memory ....
Sorry !

Ciao
Marco

 

[Gepetto]

We all have that same issue Marco

 

[Bob Boyer]

The secret of Dynaco is the output transformer e not the power tranformer .
Output tranformers must be linear and must have no saturation .
At present only McIntosh and a Swedish company ( Lundhal ) are able to build
very good output transformer and probably a Japanese company (EL ) ...

Did not know that. Thanks! I'm familiar with Lundhal's reputation; that seems to be the brand of choice for the optional transformers which customers can specify if they want the "transformer sound" in high end mix desks. And in some designs, they're not options at all.

Joe has done everything earthly possible to retain the Phase Linear sound . The basic circuit design is the same, with improvements in the implementation and component selection.

So, as someone who knows absolutely nothing about amplifier design, it's appeared to me from reading here that the improvements from the use of Joe's, Don's, and others' parts indicate improvements that go far beyond the original designs' capabilities, regardless of individual builders' implementations. Which is as it should be. Or am I reading too much into this?

For context, where I'm coming from is an experience years back when I brought a mint Dynaco PAT-4 home from the local stereo shop to assess its suitability for a vintage system. I substituted it for my Counterpoint 5000 preamp which fed an NPS-400 power amp in my main system and found the Dynaco to be "wooly" at best and in such a way that it wouldn't be a good place to start building that system. Just checked specs over at hifiengine and the Counterpoint is better but not that much; in fact, it's claimed frequency response is less than the Dynaco's (of course those numbers don't specify any tolerances for variations in those response curves). I grew up reading the mags that all preached "if it measures the same, it will sound the same" and this comparison put paid to that myth as soundly as any I can imagine. I'm guessing Mike Elliot's design was far better than Dynaco's and the vastly better components in the Counterpoint have much to do with this, as well.

So I came to the conclusion that sonic improvements between different eras of products came down to improved design and component quality. Logically, this implies that given similar circuit design, the improvements are all gained by using better components. But I'm not getting that sense here in all of the comments across the builds and sonic descriptions. I'm missing something, but what?

Thanks for the continuing education.

 

[WOPL Sniffer]

Energy Recovery??? Now I've heard it all.


HUH??????

 

[marcok]

Energy Recovery??? Now I've heard it all.


HUH??????

Oops .... a mismatch between recovery and limiter .
Ciao
Marco

 

[WOPL Sniffer]

You get another HUH??? Marco...... Quit while yer ahead.

 

[marcok]

Bob ,
I have a Dynaco system that powers a pair of AR 6 ( Pat 4 , Fm5 an St 120 ).
For me the sound is good , considering all the system , room included .
Objectively , studying the diagrams :
Pat 4 has an unregolated power supply ( unusual )
St 120 has , on the contrary , a regulated power supply ( a little unusual )
but it's a not a direct coupled power amp ( it uses a cap and inductance )
A smart solution .
In this reasoning there is a subjective part and an objective part ;
in other words : Do old devices sound worse or better compared to new ones ?
To be honest I don't know !
Ciao
Marco

 

[Gepetto]

Hi Bob
It is not a technology issue at all, no real magic here. It is an economics issue, pure and simple.

I currently own the IP necessary to produce an improved PL700 style transformer.

I designed a replacement PL700 transformer in the same E-I frame size that the original used:

• With a deeper lamination stack to eliminate the high line 50Hz 264VAC saturation issue that the existing transformers have
• With an optimized, lower loss winding to improve the load regulation over the existing
• Added a copper foil flux keeper to minimize stray flux which the existing does not have
• Added an electrostatic shield between primary and secondary which the existing does not have, many medical grade transformers have this feature
• With international windings to support the Japanese 100V market as well as rest of world which the existing does not have
• With computer modeling and simulation that the existing does not have (paid to have this process done)
• With a sheet metal based replacement for the original die cast transformer cradle.

I prototyped this beast of a transformer and the sheet metal cradle replacement and have it on one of my 700 based lab mules. The testing results bore out that it definitely was an improvement over the original. That was the goal and that was accomplished. The primary limiter in achieving even better results was the base EI frame size that PL originally chose, the window size in the E-I core ultimately limited how good that the transformer could be.

I invested >$2K in the development and prototype fabrication to get to this point.

I quoted the fabrication of this design with 30 transformer suppliers, primarily in the US but a couple in Taiwan.

I considered taking it into production for a while using the transformer manufacturer that made the proto for me. The economics just did not make sense. It would require a MOQ (minimum order quantity) that would tie up a minimum of $7K in capital for a quantity of 25, not including inbound freight which has steadily risen and would be about $35 per item in the best case. It would consume an entire 40" x 48" pallet which would have to be stored somewhere. And that would represent nearly a half a ton in weight making it nearly impossible for me to move once situated.

Add to those costs, the cost of the sheet metal cradle parts.

Add to that, the outbound freight to individual customers would have added another ~$50 in packaging and freight due to the size and weight of each transformer shipped separately. All this long before the current inflation set in.

I rapidly concluded that was a poor business proposition to entertain this thought for me and my customers and decided I had to go in a different direction...

Pics or it didn't happen.

 

[laatsch55]

Dayam....

 

[marcok]

Joe ,
from technical point of view everything is correct ,
but can you appeciate the different in sound ?
It's a provocative question to stimulate the discussion ( friendly of course )
Ciao
Marco

 

[Gepetto]

Joe ,
from technical point of view everything is correct ,
but can you appeciate the different in sound ?
It's a provocative question to stimulate the discussion ( friendly of course )
Ciao
Marco

Hi Marco
Set aside the sound quality for a moment. The overarching and original goal of all this development work was the ability to build new, better amps from the ground up without needing to find a donor 700 amp at a reasonable price.

• Lower noise floor due to less stray flux, especially on left channel where it is most prevalent due to proximity to the transformer. Achieved.
• More power output due to better load regulation and less supply sag under heavy output conditions. Achieved.

...and decided I had to go in a different direction...

 

[Bob Boyer]

Joe, I fully appreciate that it's ALWAYS about the money. Mil-spec (or better) is just gonna be extremely expensive and begins to call into question whether the incremental improvement is worth the cost, especially for anyone who is not capable and willing to spend a million dollars-plus on a system. As you're proven, it can always be done. But as you ask, at what cost?

Bob ,
...In this reasoning there is a subjective part and an objective part ;
in other words : Do old devices sound worse or better compared to new ones ?
To be honest I don't know !
Ciao
Marco

Marco - my first system was based on a Dynaco SCA-80Q I built from a kit. I thought it sounded fine at the time. But substituting a $500 Dynaco preamp for an $8400 Counterpoint (in today's dollars) designed and manufactured 40+ years after the $500 unit proved very quickly to my ears that it did not. My vintage system in the living room of the big house (Sherwood 7100 receiver/AR-XA turntable and Shure M91 ED cartridge/AR 4x speakers) only proved this further. Muddy, wooly, no soundstage, nothing, compared with my big system downstairs. In my mind, the new designs will usually win over the older designs sound-wise. Whether the cost of the new designs is worth the improvement is another question altogether.

Don't get me wrong, there's still a lot of good reasons to collect and use older gear, but I'm not so sure sound is one of them.

Regards,

Bob

 

[marcok]

It' s obvious that if you measure a new device there's no debate .
I consider the room , the speakers and the power amp as the most relevant things in a hifi system .
-the room is a " black box " with a lot of resonance peaks
-the speakers are a trasducer ( very , very difficult to design )
-the power amp should be able to drive the speakers in the best way .
It took me many years to have satisfactory result after many attempts .
I am ( better to say was ) a system engineer and this is my approach .
Not only when I was teen I received a sort of imprinting with AR speakers.
My hifi guru teached me many things as service engineer .
Joe has a designer approach .
Conclusion : every approach is necessary and the most important thing
is a friendly dialogue .
I hope I have been clear , because these are not easy concepts
and I hope to have used the correct english terms .
Ciao and let the music play
Marco

 

[WOPL Sniffer]

Hi Bob
It is not a technology issue at all, no real magic here. It is an economics issue, pure and simple.

I currently own the IP necessary to produce an improved PL700 style transformer.

I designed a replacement PL700 transformer in the same E-I frame size that the original used:

• With a deeper lamination stack to eliminate the high line 50Hz 264VAC saturation issue that the existing transformers have
• With an optimized, lower loss winding to improve the load regulation over the existing
• Added a copper foil flux keeper to minimize stray flux which the existing does not have
• Added an electrostatic shield between primary and secondary which the existing does not have, many medical grade transformers have this feature
• With international windings to support the Japanese 100V market as well as rest of world which the existing does not have
• With computer modeling and simulation that the existing does not have (paid to have this process done)
• With a sheet metal based replacement for the original die cast transformer cradle.

I prototyped this beast of a transformer and the sheet metal cradle replacement and have it on one of my 700 based lab mules. The testing results bore out that it definitely was an improvement over the original. That was the goal and that was accomplished. The primary limiter in achieving even better results was the base EI frame size that PL originally chose, the window size in the E-I core ultimately limited how good that the transformer could be.

I invested >$2K in the development and prototype fabrication to get to this point.

I quoted the fabrication of this design with 30 transformer suppliers, primarily in the US but a couple in Taiwan.

I considered taking it into production for a while using the transformer manufacturer that made the proto for me. The economics just did not make sense. It would require a MOQ (minimum order quantity) that would tie up a minimum of $7K in capital for a quantity of 25, not including inbound freight which has steadily risen and would be about $35 per item in the best case. It would consume an entire 40" x 48" pallet which would have to be stored somewhere. And that would represent nearly a half a ton in weight making it nearly impossible for me to move once situated.

Add to those costs, the cost of the sheet metal cradle parts.

Add to that, the outbound freight to individual customers would have added another ~$50 in packaging and freight due to the size and weight of each transformer shipped separately. All this long before the current inflation set in.

I rapidly concluded that was a poor business proposition to entertain this thought for me and my customers and decided I had to go in a different direction...

Pics or it didn't happen.

View attachment 75350 View attachment 75351 View attachment 75352

Joe, you didn't cancel the Black Op's program (PL1000) did you???

 

[Gepetto]

Joe, you didn't cancel the Black Op's program (PL1000) did you???

...and decided I had to go in a different direction...