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Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    ST-70 rectifier question

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    raudio44

    Posts : 17
    Join date : 2014-09-12

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    Post by raudio44 Wed Aug 18, 2021 7:23 am

    Hi, looking for some suggestions regarding my (updated original) ST-70.

    Due to Medical/Health issues and living arrangements, I haven't used it much. There are some outstanding things I finally want to clear up just to complete it.

    Not that knowledgeable and not a tech, just finally want to try and complete and use my eclectic vintage system; been a very long time since I fired it up.

    Have read in various places about whether the rectifier tube affects the sound and have seen conflicting opinions.

    Years ago (again with little experience here) I got an NOS International GZ34 made in Japan rectifier. I would like to know about what I got and if a change would be warranted. Just kind of browsing, I noted the re-issue of the Mullard.

    Have NOS Sylvania 7199s and, from a recommendation back in 2006, I have original Svetlana SED winged C EL-34s (from Upscale Audio) which I don't think even have the burn in hours. also noted Mullard re-issue 34s.

    Thoughts, recommendations welcome.

    Thanks for reading.
    Dave_in_Va
    Dave_in_Va

    Posts : 411
    Join date : 2013-04-02

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    Post by Dave_in_Va Wed Aug 18, 2021 10:06 am

    It looks to me like you're set for tubes. If that 5AR4 works, it's fine.
    Don't fret about the brand of rectifier unless you're worried about longevity. In that case look for a NOS Mullard but as they are expensive ($100 to $150) I wouldn't install one in an old amp unless I was 100% sure it was in tip-top shape.

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    raudio44

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    Post by raudio44 Wed Aug 18, 2021 12:43 pm

    Dave_in_Va wrote:It looks to me like you're set for tubes. If that 5AR4 works, it's fine.
    Don't fret about the brand of rectifier unless you're worried about longevity. In that case look for a NOS Mullard but as they are expensive ($100 to $150) I wouldn't install one in an old amp unless I was 100% sure it was in tip-top shape.

    Wasn't concerned about brand other than what I have doesn't seem to come up when seeing tube brands. Was wondering if it was a good tube. yes it works so looks like I am set, until I change speakers (which I am looking into) and see how everything sounds.

    Thanks a lot for the feedback. Appreciate it.
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    EWALAA

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    Join date : 2021-02-08
    Location : Va

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    Post by EWALAA Thu Aug 19, 2021 6:58 am

    I have the same International rectifier tubes in a pair of markIIIs. They're fine.

    EA
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    raudio44

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    Post by raudio44 Thu Aug 19, 2021 1:04 pm

    EWALAA wrote:I have the same International rectifier tubes in a pair of markIIIs. They're fine.

    EA

    Thank you for the reply. Well good to know that International is an accepted brand; really wasn't sure.
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    Jim McShane

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    Join date : 2011-10-19
    Location : South Suburban Chicago

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    Post by Jim McShane Thu Aug 19, 2021 4:55 pm

    Let me clarify a couple things here.

    1. International is a rebrander - they did not make their own tubes. So the next International tube you buy might be from Korea, or Russia, or the USA. You can't depend on the same tube being in the box as you got the last time.

    2. The Japanese made 5AR4s are VERY good tubes.

    3. The reissue Mullard is not the same tube as the old stock Mullard. For instance, the reissue has a coin base and the old Mullards had a full size base. I can't say too much about the new production Mullard since I don't carry it, but the new production Genalex and Tung-Sol are good tubes so the Mullard likely is as well. All are more durable than the Sovtek 5AR4 - and although they may not be as durable/long lived as the old stock Mullard, they are much better than the other new production rectifiers and they are much less costly.

    4. The differences in tone between various rectifier brands is mostly due to the fact that not all rectifiers (even rectifiers of the same brand) have the same DC voltage output. There is a variance from tube to tube; and this in turn means the B+ supply to the amp circuitry runs at a bit higher or lower voltage - which can have some effect on tone.

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    raudio44

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    Post by raudio44 Fri Aug 20, 2021 4:27 am

    Jim McShane wrote:Let me clarify a couple things here.

    1. International is a rebrander - they did not make their own tubes. So the next International tube you buy might be from Korea, or Russia, or the USA. You can't depend on the same tube being in the box as you got the last time.

    2. The Japanese made 5AR4s are VERY good tubes.

    3. The reissue Mullard is not the same tube as the old stock Mullard. For instance, the reissue has a coin base and the old Mullards had a full size base. I can't say too much about the new production Mullard since I don't carry it, but the new production Genalex and Tung-Sol are good tubes so the Mullard likely is as well. All are more durable than the Sovtek 5AR4 - and although they may not be as durable/long lived as the old stock Mullard, they are much better than the other new production rectifiers and they are much less costly.

    4. The differences in tone between various rectifier brands is mostly due to the fact that not all rectifiers (even rectifiers of the same brand) have the same DC voltage output. There is a variance from tube to tube; and this in turn means the B+ supply to the amp circuitry runs at a bit higher or lower voltage - which can have some effect on tone.


    Thank you for the reply and information. Learning more as I go. I understand that new issue tubes will not be the same as NOS. Thanks for the info on International. so I have a rebranded tube; wondering what I have out of curiosity. Just to do it here are a couple shots of the tube in question. As I am a novice on forums, I hope I am not going on too much. https://1drv.ms/u/s!AoIWMxfY-0bnp0Kl3Ib0AxbKN1rf?e=sg7cNl


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