The Old A-470's cloth lead vs. new production outputs ...

I have read many many times in my research how great the old output iron is in the dynaco ST-70's, and I certainly won't dispute that. I know a couple guys that bought old units all beat up just to get the old output transformers to build their amps from scratch.

I purchased two NEW production A-470's from Kevin at Dynakit for a unit that was built from the ground up. I can honestly say that the output trannies I got from Kevin are every bit as good as the old cloth lead outputs. I have rolled various tubes in and out of my scratch built unit and the old refurbished units that have cloth lead A-470's, and I cannot tell any difference whatsoever from Kevin's transformers and the old cloth lead transformers. Kevin's transformers are excellent.

Given the age of the old transformers with the cloth leads you gotta say they were extremely well built to be around half a century later still working flawlessly. There's not too many things made these days that can compare with that kind of workmanship I think. I am certainly willing to stick my neck out and say that Kevin's output transformers will be around in 2050 in my scratch built amp and my grandkids will be selling them for big money on EBAY LOL.

Don't hesitate to use Kevin at Dynakit to source output transformers. They work excellent and mine have never even gotten warm. Seriously these transformers run cool all the time for me. Offer Kevin a few extra bucks and I bet he will get some nice brass hardware for you, really looks good with the KT66 Gold Lion's by the way... :}

wolverine

[quote="wolverine"]I have read many many times in my research how great the old output iron is in the dynaco ST-70's, and I certainly won't dispute that. I know a couple guys that bought old units all beat up just to get the old output transformers to build their amps from scratch.

I purchased two NEW production A-470's from Kevin at Dynakit for a unit that was built from the ground up. I can honestly say that the output trannies I got from Kevin are every bit as good as the old cloth lead outputs. I have rolled various tubes in and out of my scratch built unit and the old refurbished units that have cloth lead A-470's, and I cannot tell any difference whatsoever from Kevin's transformers and the old cloth lead transformers. Kevin's transformers are excellent.

Given the age of the old transformers with the cloth leads you gotta say they were extremely well built to be around half a century later still working flawlessly. There's not too many things made these days that can compare with that kind of workmanship I think. I am certainly willing to stick my neck out and say that Kevin's output transformers will be around in 2050 in my scratch built amp and my grandkids will be selling them for big money on EBAY LOL.

Don't hesitate to use Kevin at Dynakit to source output transformers. They work excellent and mine have never even gotten warm. Seriously these transformers run cool all the time for me. Offer Kevin a few extra bucks and I bet he will get some nice brass hardware for you, really looks good with the KT66 Gold Lion's by the way... :}

wolverine

I hear this same line > "Nothing can compare to the old original Dynaco output transformers with the cloth leads .." I even see old original Dynaco output transformers being sold on Ebay and being advertised as having the "desirible cloth leads" as if the cloth leads made them sound any better. All of this is pure bull$%!t. Now I know it is probably unfair to compare something designed in the 1950's in light of what is available today, but suffice it to say that the output transformers made today are every bit as good as the original Dynaco output transformers. It is not hard to clone an output transformer by a little reverse engineering. All you do is carefully unwind an original Dynaco output transformer and then make note of four things.

1. The core size
2. The wire size
3. The number of turns per each winding
4. The winding technique (interleave/layered)

Any good transformer company can then program a transformer winding machine to wind a transformer that is for all intents and purposes IDENTICAL to an original Dynaco transformer. More importantly it will also SOUND LIKE an original Dynaco output transformer. Below is the wind diagram of a Dynaco A-470 output transformer as found on a Dynaco ST-70.



I am going to tell you a true story that I passed on to Kevin at Dynakitparts. I had someone from New York City purchase an ST-70 kit from me. He put it together and it worked fine and he was pleased with the sound. About 6 months later he Emailed me and told me he was going to replace the two A-470 clone transformers that came with his kit with two "original cloth lead A-470 transformers". He asked what I thought and I told him if he wanted to improve on the sound of his amp he would be better off rolling tubes in his amp. Well he went ahead and bought on Ebay two ORIGINAL cloth lead A-470's and replaced the two that came with his kit. A week later he Emails me and tells me that now one channel plays noticeably lower in volume than the other channel. I had him do a resistance check on the two transformers he bought off Ebay and lo and behold one of the windings on one transformer has a much higher resistance than the other transformer. To make a long story short he pulled his two original cloth lead transformers and put the clones back in and magically the two channels had equal volume again. Those original A-470's have looked at 430 - 450 volts for who knows how many thousands of hours and in time, even though they were well built, problems can occur.

Bob

On my rebuilt SCA 35 I had a bad time wiring in the new boards because of the cloth wired transformers, but I got it done. I do not have a lot of faith in their longevity. I will at sometime be replacing them with new set from Dynakit. I want worry free operation for years, besides things always seem to fail on weekends for me and I know that's when one would die on me. I have yet to have something crap out during the week.

Hi,
Any sonic different between the old A470 and the later Japanese winding ? Is it worthwhile to spend $200 for the A470?

Thanks.
Vichai

I believe that some make the mistake of thinking that the cachet of the cloth lead transformers has something to do with sound and I do not think that this is correct. The thing that increases the value of the cloth lead transformers for collectors is provenance. They were made by Dynaco under the guidance of Hafler, et al. They have survived a long time, and there are those that believe that the life and history of an object is at least as important as the functionality of that object. And that the two are inseperable. The Dyna transformers are, in some ways, an original, and not a copy. And even if sonically they are inferior to later, and more recent, iterations of the transformer, those transformers will never have the provenance of the original. And clearly, people are willing to put some financial premium on that. Mind you, there is nothing unique in the field of vintage audio. Most, if not all, areas of collecting put a premium on provenance. No doubt, there are those that, incorrectly, equate collectability or monetary value with enhanced sound quality. And for that matter, if you think that something should sound better, usually it will. Just my 2 cents.

viridian wrote:I believe that some make the mistake of thinking that the cachet of the cloth lead transformers has something to do with sound and I do not think that this is correct. The thing that increases the value of the cloth lead transformers for collectors is provenance. They were made by Dynaco under the guidance of Hafler, et al. They have survived a long time, and there are those that believe that the life and history of an object is at least as important as the functionality of that object. And that the two are inseperable. The Dyna transformers are, in some ways, an original, and not a copy. And even if sonically they are inferior to later, and more recent, iterations of the transformer, those transformers will never have the provenance of the original. And clearly, people are willing to put some financial premium on that. Mind you, there is nothing unique in the field of vintage audio. Most, if not all, areas of collecting put a premium on provenance. No doubt, there are those that, incorrectly, equate collectability or monetary value with enhanced sound quality. And for that matter, if you think that something should sound better, usually it will. Just my 2 cents.

It's pretty much like the people who buy NOS KT66's for $500 or more even though they're basically the same as newer reproductions that can be bought for a fraction of that price.

Yes, and it's pretty much like someone who buys an Auburn Boat Tail Speedster when the replica will outhandle it and get better gas mileage to boot.

There is about as much variability in a quality-made transformer of a given type for a given purpose as there is in a quality-made capacitor under the same parameters. All that cloth leads give is an increased chance for age-related failure. One thing is certain - removing a cloth-lead transformer for re-use is high-risk.

On eBay transformers, my Rules 1 - 3 apply:

1. Never pay more on eBay than you would be willing to throw in the trash.
2. Pictures notwithstanding - never expect more than a paper bag containing more-or-less enough parts to result in the picture(s).
3. There will ALWAYS be another one.