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    Dynakit MKIII need some help

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    scott6058

    Posts : 37
    Join date : 2009-01-21

    Dynakit MKIII need some help

    Post by scott6058 on Sat Feb 07, 2009 3:01 pm

    I just bought these very clean pair of Dynakit Mark III amplifiers.
    They included three vintage Genalex KT-88 tubes and one vintage RCA 6550 tube.
    I had thought the KT-88's were Gold Lion they were Gold Monarch does anyone know the difference? The question also is will the output tubes said to be tested good, could I have a problem with the mixed in 6550?
    I will of course follow everyone's advise in re-capping the amps.I will also have to obtain a pair of GZ34 and 6AN8's or could anyone suggest better driver tubes?
    Pictures can be seen @
    AMPS http://tinyurl.com/6o2ouh
    TUBES http://tinyurl.com/6y62rt
    Thanks and Best Regards Scott

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Dynakit MKIII need some help

    Post by Bob Latino on Sat Feb 07, 2009 6:24 pm

    Scott,

    The amps look to be in good shape. What I would do is this > Save one the 6550 and one of the KT88's as spare tubes and buy one matched PAIR of Genalex Gold Lion KT88's ($100) and use the new KT88's in one of the amps. It is not a good idea to mix a KT88 and a 6550 in one matched pair especially with the original Dynaco bias system which only biases output tubes as "pairs". KT88's and 6550 tubes although similar have slightly different characteristics. A KT88 will handle more plate voltage than a 6550. I don't think you will have a "problem" using a KT88 and 6550 tube together but because of the slightly different characteristics they won't "push/pull" exactly together and you won't get all that you can from the amp with a mixed pair.

    As to the 6AN8. IMHO it's not the best sounding tube around. It is a pentode/triode similar to 7199 tube used in the original ST-70. Tubes4hifi makes a nice replacement driver board for the Mark III that uses 12AT7 tubes. You could consider replacing both driver boards. You would get a nice increase in sound quality from your Mark III's with the VTA Mark III driver board. You can find out about the VTA Mark III boards at the link below.

    VTA Mark III driver boards

    Bob

    scott6058

    Posts : 37
    Join date : 2009-01-21

    MKIII Help

    Post by scott6058 on Sun Feb 08, 2009 12:37 am

    Thanks Bob
    Makes sense to me. Thanks for the swift reply.
    I will work on the list and get an order out soon.
    If you could choose a good output tubes for my st-70 what would you consider,,,,, not vintage NOS?
    Best regards Scott

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Dynakit MKIII need some help

    Post by Bob Latino on Sun Feb 08, 2009 8:52 am

    scott6058 wrote:Thanks Bob
    Makes sense to me. Thanks for the swift reply.
    I will work on the list and get an order out soon.
    If you could choose a good output tubes for my st-70 what would you consider,,,,, not vintage NOS?
    Best regards Scott

    Scott,

    The sound of vintage tubes many times is hyped beyond their actual value. Having a new or near mint quad of Mullard EL34's is nice and they do sound good but are probably way overpriced in relation to the quality of sound produced. JJ KT77's sound really good but some of them have quality control issues that you could have to deal with. The best NEW current production output tube out there now for the ST-70 (IMHO) is the Genalex Gold Lion KT66 (not the KT88). These tubes are very well made and fairly expensive > maybe $150 per quad ? They are the best sounding output tubes I have found in my own VTA board driven ST-70. I actually have a quad of original Mullard EL34's here but I like the sound of these KT66's even better. Photo below of my personal Dynaco ST-70 with a quad of Genalex Gold Lion KT66's..

    Bob



    scott6058

    Posts : 37
    Join date : 2009-01-21

    MKIII's vs ST70

    Post by scott6058 on Sun Mar 15, 2009 11:30 am

    Hi Bob
    It seems my ST70 outperforms the MKIII's.
    I was wondering if your offer still stands on the VTA's
    Thanks again for all your help.
    Best regards Scott

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Dynakit MKIII need some help

    Post by Bob Latino on Sun Mar 15, 2009 11:48 am

    scott6058 wrote:Hi Bob
    It seems my ST70 outperforms the MKIII's.
    I was wondering if your offer still stands on the VTA's
    Thanks again for all your help.
    Best regards Scott

    Hi Scott,

    The offer still stands on the assembled VTA Mark III driver boards that I have here.

    Email me directly at Bob01605@aol.com from your normal Email address and I can explain what I have in more detail off the forum board here.

    Bob

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