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The Dynaco Tube Audio Forum

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 Two Year Birthday

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    Post by 1MOR Wed Feb 01, 2012 12:15 am

    The ST-70 that I purchased from Bob as a kit, is about to celebrate its second birthday. Upgrades made since the purchase include Gold Lion reissue KT-66s, two Mullard CV 4024s and a 1958 Holland Bugle Boy ECC81 in the phase splitter position. I also found that the Amperex 7062 is an impressive tube, and cheap. The Ruby GZ34 that Bob supplied has been upgraded to a Mullard GZ33.

    Great amp, thanks Bob! Very Happy

    [img]ST-70 Two Year Birthday P1010010[/img]

    [img]ST-70 Two Year Birthday P1010011[/img]
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    Nicola
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    Post by Nicola Wed Feb 01, 2012 12:15 pm

    Wow, it looks really great! I believe it sounds very good too!
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    Post by akb1022 Wed Feb 01, 2012 12:39 pm

    How do you keep you chrome so clean and shiny...mine looks a little dule...
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    Bob Latino
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    Post by Bob Latino Wed Feb 01, 2012 4:01 pm

    akb1022 wrote:How do you keep you chrome so clean and shiny...mine looks a little dule...

    His chassis is not a chrome plated chassis. It is one of the mirror polished stainless steel chassis supplied with the VTA amp kits ...

    Bob
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    Post by akb1022 Wed Feb 01, 2012 4:04 pm

    any suggestions on how to "shiny" it up?
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    Post by Tube Nube Wed Feb 01, 2012 4:05 pm

    I wonder if you noted any sonic difference with the mullard rectifier?
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    Post by Bob Latino Wed Feb 01, 2012 4:08 pm

    akb1022 wrote:any suggestions on how to "shiny" it up?

    Any metal polish works fine - or that plastic polish "Flitz" works OK also. Just be careful around the lettering or you can polish the lettering right off the amp. Recommendation - Use Q-Tips to polish "around" the lettering on the front and rear face of the amp.

    Bob
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    Post by 1MOR Wed Feb 01, 2012 10:24 pm



    Tube Nube wrote:I wonder if you noted any sonic difference with the mullard rectifier?

    No improvement noted. This was a NOS tube that came off the auction site and went at a very low price, lower than the average used Mullard GZ34. There was no change in bias after I removed the Amperex/Mullard GZ34 and replaced it with the GZ33. Otherwise, it looks rather retro with the KT66s.

    The GZ33 will pass a little more current than the GZ34. This would probably lead to a performance improvement in Bob's larger amps. I think Bob would be more qualified to comment on that issue.

    The center 12AT7 made the biggest improvement in the amp's performance, at least in my opinion.


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    Post by 1MOR Wed Feb 01, 2012 10:30 pm

    akb1022 wrote:How do you keep you chrome so clean and shiny...mine looks a little dule...

    I always thought that a shiney chassis makes any amplifier sound better. Mine is so shiney, the amp still sounds great even when its turned off! LOL

    Bob certainly hit it out of the park with the stainless steel chassis. These look even better in person.
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    Post by evgenibgr Mon Mar 05, 2012 8:48 am

    I wonder what is sonic difference with the Mullard CV 4024s and a 1958 Holland Bugle Boy ECC81 in center position?




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    Post by mantha3 Tue Mar 06, 2012 3:50 pm

    I put in a post months ago about the 7062 tube in place of a 12AT7. I find it sounds excellent as well. I have a couple Amperex 7062s and have been tempted to buy Mullard 7062s

    I run GZ33 and GZ37s in place of the GZ34s... Sound wise I don't hear a change but I love the look of those big old tube rectifiers.

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    Post by evgenibgr Tue Mar 06, 2012 5:15 pm

    mantha3 wrote:I put in a post months ago about the 7062 tube in place of a 12AT7. I find it sounds excellent as well. I have a couple Amperex 7062s and have been tempted to buy Mullard 7062s

    I run GZ33 and GZ37s in place of the GZ34s... Sound wise I don't hear a change but I love the look of those big old tube rectifiers.

    My future amp ST-70 is still on Bob working table Rolling Eyes . But I already think about a future upgrade of the tubes. Embarassed I found these: http://www.ebay.com/itm/270919093870?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
    and wonder whether they are better than Mullard CV4024.
    I bought Mullard GZ34. I hope this is a good choice. How much is the life of Mullard vs Rubi rectifier?
    ST-70 Two Year Birthday Kgrhqr11
    First power tubes will be Genelex Gold Lion KT66. May be next choice will be ShuGuang TREASURE Tubes KT88-Z or KT66-Z (very expensive). Are thay better vs GL?
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    Post by mantha3 Tue Mar 06, 2012 6:41 pm

    Amperex Bugle Boy are nice.. Better than Mullard? Don't know... both are great and have a good following. That Langrex is a good e-bay vendor. I've done business with them buying Mullard GZ33s.

    Mullard GZ34s are the best. I have some Sylvania Big Bottle old GZ34s that are good too. Fat suckers. New issue Rubys?

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    Post by RockyAM Fri Mar 09, 2012 10:40 am

    I've had my VTA ST-70 for almost 2 years now ... It still plays just fine. I did lose a couple of rectifier tubes over that time but the power tubes and driver tubes are the original tubes and they still play fine. I will probably replace the output tubes at least pretty soon. I know that Bob likes the GL KT66 output tubes for the ST-70 but they are kind of expensive. Any suggestions for less expensive output tubes for this amp? RockyAM


    Last edited by RockyAM on Thu Dec 20, 2012 10:26 am; edited 1 time in total
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    Post by evgenibgr Fri Mar 09, 2012 10:46 am

    RockyAM wrote:I've had my VTA ST-70 for almost 3 years now ... It still plays just fine. I did lose a couple of rectifier tubes over that time but the power tubes and driver tubes are the original tubes and they still play fine. I will probably replace the output tubes at least pretty soon. I know that Bob likes the GL KT66 output tubes for the ST-70 but they are kind of expensive. Any suggestions for less expensive output tubes for this amp? RockyAM

    I read very good reviews for Russian 6N3cE.
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    Post by Feistygoat Fri Mar 09, 2012 6:28 pm

    So the GZ33 can be used in a standard ST-70 without creating any issues/problems?
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    Post by erlingt Sat Mar 10, 2012 7:16 am

    Yes, I run a VTA ST-70 with a Mullard GZ33, and have done it for now nearly 2 years.
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    Post by 1MOR Mon Mar 19, 2012 10:48 pm

    evgenibgr wrote:I wonder what is sonic difference with the Mullard CV 4024s and a 1958 Holland Bugle Boy ECC81 in center position?

    Mullard CV4024s provide more detail, air around instruments. I have a matched pair of Siemens NOS ECC801S as replacements for the Mullard CV4024s, but prefer the Mullards. I tried a CV4024 as the center tube but noticed an improvement with the 7062 in place. The BB opened up the soundstage, giving a sense of a 3D image. I have an Amperex pinched waist 7062 that is a close second to the BBs.

    I bought a few+ of the BBs off the auction site. They were all used pulls. One tested very low, one tested as having a short(deadly if used in an amp), and another had dropout/noise problems. I run all tubes through a tester prior to installing in the amp.

    NOS Pairs of RCA 5965 black plates and Mullard E180CC await their turns.
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    Post by 1MOR Mon Mar 19, 2012 11:24 pm


    mantha3 wrote:I put in a post months ago about the 7062 tube in place of a 12AT7. I find it sounds excellent as well. I have a couple Amperex 7062s and have been tempted to buy Mullard 7062s

    I had the same experience with the 7062. The JAN Phillips 7062 tubes were available in quantity and quite reasonable right after I completed this amp. The older Aperex orange globe and pinched waist 7062s were better still but, seem to have dried up. The blue labeled German Valvo 6201 is reported to be something special. That tube is on my bucket list.

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