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    OPT Choices for ST70

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    gener8r

    Posts : 59
    Join date : 2012-04-28

    OPT Choices for ST70

    Post by gener8r on Fri Jun 23, 2017 5:01 am

    Besides the A470s, can A431s be used as the OPTs in an ST70 setup using the PA60 as the PT?

    Edcore makes the CXPP60-4.2K, which seems to be identical to the A470 as far a specs and less expensive at $80.00, but has a six week lead time.   I wonder how it sounds in comparison to the above two?

    I also found these on ebay for $34.00;

    http://www.ebay.com/itm/Basler-Tube-Amp-Output-Transformer-4500-Ohm-CT-To-4-8-16-Ohm-40-Watt-BE32748001/191874105549?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

    Has anyone tried these?  Would anyone try these?

    I have also found a couple of OPTs with the same specs as the A470, but are listed as "guitar amp OPTs".  What's the difference?

    Thanks in advance.
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    Peter W.

    Posts : 455
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: OPT Choices for ST70

    Post by Peter W. on Fri Jun 23, 2017 7:46 am

    I would be concerned about distortion were the Mexican transformers operated at rated load.
    I see a great many Edcore transformers in various tube designs, including Dynaco clones. By direct observation, they seem to do a good job. I have not used them personally.
    The A431 is designed against a much lower output - typically 6BQ5s in PP as per the ST & SCA 35 units.
    Some things cannot be rushed.
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    gener8r

    Posts : 59
    Join date : 2012-04-28

    Re: OPT Choices for ST70

    Post by gener8r on Fri Jun 23, 2017 11:02 am

    Did you mean the 565 OPT (ST35) at 17 watts as opposed to the 431 (MKIII) at 60 watts?

    So my question is still can the 431 be substituted for the 470 in a ST70 setup that's using the PA60 PT?

    Triode seems to be the only one with 470s right now, and they are not my first choice for various reasons.

    Again, Thanks.

    ramon68

    Posts : 97
    Join date : 2009-04-12
    Age : 76
    Location : naples fl

    Re: OPT Choices for ST70

    Post by ramon68 on Fri Jun 23, 2017 11:11 am

    What about Dynakitparts.com for those trannys?
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    Peter W.

    Posts : 455
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: OPT Choices for ST70

    Post by Peter W. on Fri Jun 23, 2017 12:02 pm

    gener8r wrote:Did you mean the 565 OPT (ST35) at 17 watts as opposed to the 431 (MKIII) at 60 watts?

    So my question is still can the 431 be substituted for the 470 in a ST70 setup that's using the PA60 PT?  

    Triode seems to be the only one with 470s right now, and they are not my first choice for various reasons.

    Again, Thanks.  

    You are absolutely correct on the OPTs!

    And, yes, you may use the A431 for the 6CA7 family of tubes, it will run a touch cooler as well.

    Been there.

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