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    ST70 vs MK3

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    pjp3

    Posts : 39
    Join date : 2013-03-19
    Age : 54
    Location : Pelham, AL

    ST70 vs MK3

    Post by pjp3 on Fri Aug 30, 2013 10:51 am

    I'm thinking about upgrading from my ST70 to the mono blocks and would like to hear
    feedback on the difference in sound.

    corndog71

    Posts : 453
    Join date : 2013-03-19
    Location : It can get windy here

    Re: ST70 vs MK3

    Post by corndog71 on Fri Aug 30, 2013 12:19 pm

    I've owned an ST70 and still own a pair of Mark IV's. Monoblocks are cool and sexy and all but they can also be a pain. With the ST-70/120 you only have one rectifier tube to worry about vs 2 with monoblocks. With monoblocks you need 2 AC outlets vs one with a stereo amp.

    I don't think you'll miss anything power or sound quality-wise going either way. Sure the Mark IV's are rated 40 watts vs. the ST70's 35 watts but I doubt the difference would be noticeable. The ST120 is a viable alternative to a pair of Mark III's and one that I'm looking at myself. I've lusted after the Mark III's for years but after having lived with the Mark IV's for several years, the novelty of monoblocks has worn off. A stereo amp is just more convenient, compact and easier to work with in my opinion.

    It's up to you though. Monoblocks are pretty cool to look at and they allow you to spread them out closer to the speakers if you like.

    or not...

    PeterCapo

    Posts : 386
    Join date : 2008-12-05

    Re: ST70 vs MK3

    Post by PeterCapo on Fri Aug 30, 2013 1:08 pm

    Well, you’ll get a little more power with the Mark IIIs; with each Mark III having its own power supply there should overall be a bit more oomph. There is also the fundamental difference in the sonics of the output tubes. EL34s tend to be a bit more laid-back, some say more “tubey” sounding, and I have thought even “slow” sounding in some cases, but that is not to say that an EL34 amp is not enjoyable. KT88 in the Mark III should have a bit more sparkle and clarity, I think. Which you prefer would depend on your taste. I appreciate both for their respective qualities.

    GP49

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    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: ST70 vs MK3

    Post by GP49 on Sat Aug 31, 2013 12:14 pm

    Monoblocks can introduce ground loop issues, especially if one follows the "belt-and-suspenders safety" advice of some and grounds everything separately via its own three-wire cord.

    Tiziano73

    Posts : 29
    Join date : 2012-09-11
    Location : Italy

    ST70 vs MK3

    Post by Tiziano73 on Thu Sep 05, 2013 1:48 pm

    I have an ST70 and a pair of Mark III's. They are really different but wonderful amplifiers.
    I agree with PeterCapo post but in my opinion i prefer MK3.

    Regards

    Tiziano

    j beede

    Posts : 328
    Join date : 2011-02-07
    Location : California

    Re: ST70 vs MK3

    Post by j beede on Thu Sep 05, 2013 1:50 pm

    No comparison in my experience driving Quads, Magneplanars, Mission 2-ways, etc. My ears choose MkIII over my Threshold, Forte, VTL (EL-34). Just say "no" to the quad cap. I left the failed quad caps in place just to avoid exposing a hole in the chassis--they are not connected (excpet grounding). The cap boards I built were designed to attach tot he underside with no mods to the chassis. I did not increase the cap values--as is commonly done--to keep my 5AR4s happy. More is not always better. I am pre-rectifying with 1n4007 ahead of the 5AR4 (yellow sheet mod). I consider that a must-do.
    ...j

    " />

    pjp3

    Posts : 39
    Join date : 2013-03-19
    Age : 54
    Location : Pelham, AL

    Re: ST70 vs MK3

    Post by pjp3 on Thu Sep 05, 2013 2:13 pm

    Thanks for the replies.
    I'm now looking between a VTA ST120 or find a pair of MK3's.

    Not that there is anything wrong with ST70, I may pass it down to
    my daughter for Christmas.

    Any one know of a set of MK3's for less than $1000?

    hawaii.ken

    Posts : 157
    Join date : 2012-01-31

    Re: ST70 vs MK3

    Post by hawaii.ken on Thu Sep 05, 2013 3:28 pm

    There's was a pair on fleaBay recently sold (1hr ago). They do come up for sale regularly.
    http://www.ebay.com/itm/181210461002

    DynakitParts
    Admin

    Posts : 183
    Join date : 2008-11-30

    MK III amps

    Post by DynakitParts on Thu Sep 05, 2013 4:18 pm

    pip3,
    We sell new Dynakit MK III amp kits for $500 each......Version (B).

    Why buy a used pair & then spend $$ to restore them?

    Kevin @ Dynakit

    pjp3

    Posts : 39
    Join date : 2013-03-19
    Age : 54
    Location : Pelham, AL

    Re: ST70 vs MK3

    Post by pjp3 on Thu Sep 05, 2013 4:38 pm

    DynakitParts wrote:pip3,
          We sell new Dynakit MK III amp kits for $500 each......Version (B).

    Why buy a used pair & then spend $$ to restore them?

    Kevin @ Dynakit
         
    Version (B)?

    DynakitParts
    Admin

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    Dynakit MK III

    Post by DynakitParts on Thu Sep 05, 2013 9:21 pm

    We offer two (2) Versions...

    (A) with carbon composition resistors

    (B) with metal film resistors

    Most choose the Version (B)

    As noted on our website....I will be gone for a week's vacation leaving on Friday. If you have any questions...call me when I return on 09-16-13.

    Regards,

    Kevin

    hawaii.ken

    Posts : 157
    Join date : 2012-01-31

    Re: ST70 vs MK3

    Post by hawaii.ken on Fri Sep 06, 2013 4:48 am

    DynakitParts wrote:pip3,
          We sell new Dynakit MK III amp kits for $500 each......Version (B).

    Why buy a used pair & then spend $$ to restore them?

    Kevin @ Dynakit
         
    Add about $200 for tubes = $1200

    peterh

    Posts : 679
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: ST70 vs MK3

    Post by peterh on Fri Sep 06, 2013 5:52 am

    hawaii.ken wrote:
    DynakitParts wrote:pip3,
          We sell new Dynakit MK III amp kits for $500 each......Version (B).

    Why buy a used pair & then spend $$ to restore them?

    Kevin @ Dynakit
         
    Add about $200 for tubes = $1200
    Tride electronics adds $113 for tubes.
    and the end result is 2 brand new amps where everything is supportable and with some warranty.

    Luddite

    Posts : 235
    Join date : 2009-02-04
    Age : 66
    Location : Texas

    Re: ST70 vs MK3

    Post by Luddite on Fri Sep 06, 2013 11:13 am

    peterh wrote:
    hawaii.ken wrote:
    DynakitParts wrote:pip3,
          We sell new Dynakit MK III amp kits for $500 each......Version (B).

    Why buy a used pair & then spend $$ to restore them?

    Kevin @ Dynakit
         
    Add about $200 for tubes = $1200
    Tride electronics adds $113 for tubes.
    and the end result is 2 brand new amps where everything is supportable and with some warranty.
    FYI, that addition would be $113.00 per each amplifier for tubes...total $226.00

    Best Regards,
    Charlie

    pjp3

    Posts : 39
    Join date : 2013-03-19
    Age : 54
    Location : Pelham, AL

    Re: ST70 vs MK3

    Post by pjp3 on Fri Sep 06, 2013 11:42 am

    I have been told the transformers in the old units sound much better than the newer transformers.

    DynakitParts
    Admin

    Posts : 183
    Join date : 2008-11-30

    MK III Amps

    Post by DynakitParts on Fri Sep 06, 2013 12:44 pm

    Then buy an old pair of MK III's

    Kevin

    sailor

    Posts : 269
    Join date : 2011-04-04

    Re: ST70 vs MK3

    Post by sailor on Fri Sep 06, 2013 1:11 pm

    The problem I have seen with the old Mark III is they sell for to much money. The chassis are pitted and rusted, the caps, boards and sockets need to be changed out and many have had to replaced burned out power transformers. The assumption is the tubes are in good shape which is not always the case. As for the output transformers, they need to be the American made cloth lead verity. The others were made in Japan.
    As far as sound, I have owned both Stereo 70's and Mark III. I personally think the EL-34 used in the Stereo 70 is a midrange tube with poor Bass and Treble. If you change them out for big bottle EH 6ca7 The 70 sounds as good as the mark III just half the power. Just my opinion.

    corndog71

    Posts : 453
    Join date : 2013-03-19
    Location : It can get windy here

    Re: ST70 vs MK3

    Post by corndog71 on Fri Sep 06, 2013 2:57 pm

    My rebuilt ST70 with Curcio driver and cap boards sounded pretty damn good top to bottom.


    peterh

    Posts : 679
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: ST70 vs MK3

    Post by peterh on Fri Sep 06, 2013 3:35 pm

    pjp3 wrote:I have been told the transformers in the old units sound much better than the newer transformers.
    Don't listen to rumors.

    Listen on amps and trust your ears.


    PeterCapo

    Posts : 386
    Join date : 2008-12-05

    Re: ST70 vs MK3

    Post by PeterCapo on Fri Sep 06, 2013 4:13 pm

    I personally have never done a careful comparison of the sound of the original transformers vs. the new, reissue transformers.  I can say that I have the Dynakitparts transformers in my stereo 35 and Stereo 70, and both amps sound great.

    Buying an original pair of Mark IIIs could easily mean the possibility of rework to one degree or another, which would only add to the overall cost and tedium given some of the requirements of reworking an original.  Unless part of your purpose is to enjoy restorative work, or just to experiment, my opinion is that choosing the new Dynakitparts Mark III is preferable.


    Last edited by PeterCapo on Sat Sep 07, 2013 3:55 pm; edited 2 times in total

    Bob Latino
    Admin

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    Join date : 2008-11-26
    Location : Massachusetts

    Re: ST70 vs MK3

    Post by Bob Latino on Fri Sep 06, 2013 5:42 pm

    pjp3 wrote:I have been told the transformers in the old units sound much better than the newer transformers.
    This is probably one of the most repeated pieces of misinformation that continues to float around the internet. It is not that hard to "clone" a power or an output transformer. All you need to know are five things. The core size, the wire size, what the laminations are made of (M6 or M19 laminations), the number turns per winding and the winding technique (usually interleaved layered primary/secondary windings). Any respectable transformer company can then use these facts to program a transformer winding machine to create a transformer that is identical to any older or vintage transformer.

    Below is a photo of the number of windings on an original Dynaco A-470 output transformer and where the primary and secondary wires are tapped into the windings. The A-470 output transformer found in the VTA ST-70 amp kits is a clone of the original and uses M6 silicon steel laminations which have a better inductance transfer from the primary to the secondary than the cheaper M19 laminations found in most Chinese amps. I have also heard the Dynakitparts version of the A-470 and it also is well made and sounds great. I am assuming that it is also a copy of the original A-470. There is no need to search the net for "vintage transformers" and making the assumption that they are better made than todays transformers. In the original Dynaco ST-70 amp the only good things were the OUTPUT transformers and the Mullard tubes. If you buy an ST-70 on Ebay as a "fixer upper", the Mullard tubes have probably long since been replaced. So what are you left with - two very well made OUTPUT transformers. The power transformer was way undersized and does allow the amp to work but has poor power transfer capabilities. All modern clones of the Dynaco PA-060 power transformer (VTA amps, Dynakitparts or Triode Electronics) have higher stack laminations and are ALL better than any original Dynaco PA-060 POWER transformer.

    Forgive me for the rant here but everytime I hear this "internet factoid" about the wonderful "original cloth lead A-470 output transformer" being "untouchable for sound quality" I want to cringe.

    Bob




    Captain Coconut

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    Re: ST70 vs MK3

    Post by Captain Coconut on Fri Sep 06, 2013 6:22 pm

    Too often, these factoids or rumours become fixed in stone. Nobody takes the time to logically consider the facts. It's like people believing all silver wiring is bright sounding and copper wire is mellow. Guess what, silver is brighter looking than copper, so it has to sound brighter, right?

    As far as the transformers go: who has had the opportunity to compare two ST-70's, one with vintage OPT's and one with modern OPT's, and everything else being EXACTLY the same. Same caps, same resistors with exactly the same values, same connectors, same tubes with exactly the same parameters. And to top it off, doing a blind listening session. My guess is that nobody has done it. So nobody can state for sure if the old transformers are better sounding than the new ones. Heck, it's even possible that the new OPT sounds better than the old one.

    So there!  Very Happy

    sailor

    Posts : 269
    Join date : 2011-04-04

    Re: ST70 vs MK3

    Post by sailor on Fri Sep 06, 2013 9:11 pm

    I think my wording was taken out of context. When I referred to the cloth lead American transformers compared to the regular wire Japanese I was referring only to the old Dynaco stuff not the new Clone transformers. I have heard 2 Stereo 70 and 2 SCA35 [total of 4 amps] side by side with one of each having the American and the other 2 having the old Japanese transformers. The 70 and the 35 with the American transformers had far better bass. The Japanese versions rolled of the bass to produce a little more musical mid range. I don't know if they used different material than the American version or just less quality control which in those days was common for Japanese products. After all I had a toy car in the late 50's that came from Japan and was made from a steel beer can. It fell apart almost immediately. But what ever the reason the difference is very very apparent. I even went so far as to exchange the tubes and the outcome was the same. The Japanese transformers had a lot less Bass.
    Very important: The above comment has nothing to do with present day "Clones" which I am sure are as well or better built than the original American made Dynaco transformers. I can not comment on them as I have never owned or heard any of them. However, I do think most people would be far better off buying one of the new kits rather than paying to much for one of the old ones and sinking hundreds of more dollars fixing it up. If I was offered one of the old amps or one of the new kits I would take the new Kit.
    By the way Bob thank you for the info about M6 and M19. I didn't know. There is always something new to learn on these Audio boards.

    kygeezer

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    Re: ST70 vs MK3

    Post by kygeezer on Sat Sep 07, 2013 12:40 pm

    I must add my two cents!  I have two upgraded Mark IIIs, one with the original output transformer (cloth leads) and one with Kevin's "clone" output transformer.  I have been using them for about 3 months and have switched them from right to left and back and cannot hear any difference.  My ears are used to hearing classical music through decent or better stereo systems for many years, so I think my ears are a little better than average.

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