A470 Transformer Choices

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A470 Transformer Choices

Postby joeztech » Sat Sep 06, 2014 7:39 am

I see A470 output transformers from Dynakitparts.com and Triode Electronics. They are within a few dollars of each other. Are there any reasons why one would be a better choice than the other? Or, are there other choices that are just as good?

Joe
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Re: A470 Transformer Choices

Postby Geek » Sat Sep 06, 2014 2:54 pm

Hi,

If you haven't drilled your chassis yet, I'll toss this one into the mix as well:
https://edcorusa.com/cxpp60-ms-4_2k O:)

What is it you're after? Pure, unadulterated vintage sound? Then forget all but NOS or maybe a used pair off of Ebay. If you want ST-70 as-good-as-it-gets-today, get a Triode kit and play with driver boards (Shannon has a nice one, so do other members here).

Cheers!
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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Re: A470 Transformer Choices

Postby joeztech » Sat Sep 06, 2014 3:20 pm

As a starting point I have modified the existing PC board to use 6GH8A tubes instead of 7199s. At some future date I plan to use one of the replacement boards that use triodes in a long-tailed-pair circuit with triode driver/inverters before the output tubes. I am leaning toward the VTA-70 boards so far, but no decision has been made on that yet.

I had already ordered a new stainless steel chassis from dynakitparts.com. Today I also ordered a new A470 transformer from them and a hardware kit for mounting tube sockets etc. I already have some new electrolytics on hand to make improvements to the power supply. I think I will start by using the existing 5AR4/GZ34 rectifier, but may build a plug-in solid state replacement to try too. Dynakitparts is combining all the pieces to reduce shipping costs for me. I don't insist on using OEM old transformers with the cloth covered leads, just a transformer made to match the original units as to design and performance. When I first posted the request for recommendations, I had not spotted some of the older posts on this subject. Based on comments and reviews of various units I went with the Dynakitparts unit. The Triode and Edcore units are fine products too and I am sure they would be good choices as well.

I looked at the YouTube video comparing THD measurements of 7199s versus 6GH8As and liked what I saw. One other tube type not tested would be a 6EA8 type which is often used as a substitute for a 6GH8A and vice-versa.

Thanks for the suggestions.

Joe
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