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    Mark III Transformers

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    Wild Bill

    Posts : 1
    Join date : 2011-08-18
    Location : Virginia Beach, VA

    Mark III Transformers

    Post by Wild Bill on Fri Aug 19, 2011 5:39 am

    Hi all. First off I have to state that I'm a newbie to this forum and also to the tube amplifier world. I searched the forum for an answer and didn't find one that exactly answered my question. So I'm hoping to get a definitive answer from the experts here.

    I plan on building a pair of Mark III's from scratch rather than buying a kit or rebuilding / reworking a used pair. As the title says, I have a question about the transformers.

    I found an Edcor Power transformer (XPWR011-120) with identical specs as the Dynaco. I'm wondering if this a suitable substitute?

    I also found an Edcor Output transformer (CXPP60-MS-4.2k), but it's rated at 4200 ohms vice the 4300 ohms that's used in the Mark III. Can this be used? If so, what changes / mods need to be done? Or is the 100 ohm difference negligable? As far as I can tell, every other spec relating to this transformer matches the Dynaco A-431 specs.

    Thank you in advance for any info you can provide.

    - Bill

    Bob Latino
    Admin

    Posts : 2414
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Mark III Transformers

    Post by Bob Latino on Fri Aug 19, 2011 7:28 am

    Hi Bill,

    The Edcor XPWR011-120 power transformer and the Edcor CXPP60-MS-4.2k output transformer are electrically almost the same as the Dynaco P-782 power and Dynaco A-431 output transformer. You are correct in the the 4200 ohm vs. the 4300 ohm difference on the Edcor and Dynaco output transformers is negligible. However > Neither the Edcor CXPP60-MS-4.2k output transformer nor the Edcor XPWR011-120 will physically fit the bolt hole pattern on the Dynaco Mark III chassis. The only way you could use these transformers is to make up a Mark III is to (A) build your own chassis OR (B) drill holes on the stock chassis to make them fit. The other thing to think about is that any "custom build" will always be looked upon with suspicion and be worth less should you ever decide to sell your amps some time down the road. In other words, an original looking Dynaco Mark III or a build of a brand new Mark III will always be worth more than than a custom version Mark III built on an "alien" chassis. Also, when you buy parts piecemeal (driver board, tube sockets, quad cap, choke etc.) it will cost you more for the parts than if you purchase a complete kit.

    If you are looking to build a pair of Mark III's my recommendation is to get two Dynaco Mark III kits from Dynakitparts. When you buy a full kit, the price of each item is somewhat discounted and the total price you will pay is less. When you are finished, the amps will look just like an original Mark III and have greater value if you do decide to sell them at some time.

    Bob


    Last edited by Bob Latino on Fri Aug 19, 2011 1:18 pm; edited 1 time in total

    zx

    Posts : 194
    Join date : 2011-08-05

    Ck out these guys

    Post by zx on Fri Aug 19, 2011 10:06 am

    http://diyaudioprojects.com/Forum/

    Thay use a lot Edcor,i have all so used Edcor thay are hand made in the USA to oder,vary fair$$

    Thanks Bob for the site

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