The upcoming "new" Dynaco ST-70x - opinions?

Discussion in 'Audio Hardware' started by Benzion, Apr 21, 2017.

  1. Davey

    Davey define a transparent dream

    Location:
    SF Bay Area, USA
    Think I'd probably get the VTA ST-70 if inclined to explore the Dynaco mystique, either kit or assembled ...

    [​IMG]
     
  2. rl1856

    rl1856 Forum Resident

    Location:
    SC
    $3k ? So much for an amp that anyone can afford. The original ST70 was the Model T of stereo tube amps. Cheap, worked well (enough), sounded good (enough) and mostly reliable. Discounting for inflation, this $3k ST70 would have been about $500 in the mid 60's....or about 2x more expensive than a Mac MC240.....

    There are many amplifiers both new and used available for $3k (or less) that will sound much better than this new ST70 could ever possibly hope to. HK Citation II anyone ? Easily found for about $1000-$1500, and another $1k for restoration..... Several ARC and CJ tube amps..... Line Magnetic, Rogue, Prima Luna....
     
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  3. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    Seattle, WA
    Exactly. The original appeal of the stereo 70 was that it was a cheap, and easy to assemble amp kit which contained better than average output transformers. It was made as simple s design as could be made to build a push-pull 35 wpc amp in its day.

    The later appeal was to modders who figured-out that stereo 70s original circuit could be improved upon quite a bit by various mods, and that this amp could sound great with the right mods. This has fuled cottage industries from the late 70s on who love to rebuild these amps into some really nice sounding little amps. I purchased and built an audio-research kit for my stereo 70 back in the early 80s (which I still have to this day), and it transformed the sound of this little amp into something very special.

    But there has always been one problem with all of these mods: limited space inside of the chassis to fit a the kind of beefy power supply which is required to take any of these new designs to their limits.

    Frankly this new amp is only a stereo 70 in terms of its form factor, and possibly in terms of its transformer designs. Other than that, this is really a completely new design. The big mistake with doing this is that the stereo 70s original form factor was the biggest limiting factor to any of its mods. Plus most people who are interesting in the stereo 70 know that there are already a couple of upgraded clones available for a lot less than this new unit is selling for. So I have a difficult time envisioning much of a market for a yet another new stereo 70 which sells for much more than does its very similar competition.
     
  4. allied333

    allied333 Forum Resident

    Location:
    Fenton, MI
    It looks like a winner to me. Addresses the original stellar output transformers with supplying same quality as original. Tube rectifier is not needed as newer SS diodes operate as quiet as the 5AT4 tube and likely supplies a hefty current surge for deep bass notes. Another plus is not using the so-so sounding 7199 tube. Only issue I have is a 12AU7 driver/phase splitter. Phase splitters are not known for being particular with regard to tube quality, but simply use a 6SN7 to 12AU7 socket adapter and a Sylvania 6SN7GTA. If you must go with 12AU7, use CBS Hytron 5814 or Brimar 13D5.

    Note- when the 12Au7 was newly released, a year later Collins Radio complained about the 12AU7 high distortion. RCA revised the 12AU7 and released the new 5814 tube as a lower distortion 12AU7.
     
    Last edited: Jul 6, 2018
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  5. simon-wagstaff

    simon-wagstaff Forum Resident

    I have had one for many years. It worked magic with my Infinity IM 4.1s. (Well, his U70, which is basically the same thing)
     
  6. Ghostworld

    Ghostworld Forum Resident

    Location:
    US
    I sold mine like a fool before I even hooked it up (moving) because I had a one-year-old and was worried about him burning himself. In hindsight, sometimes, one has to take a few risks....
     
  7. sushimaster

    sushimaster Forum Resident

    Got one off eBaY. Going to do a head to head Van Alstine Ultravalve vs Van Alstine Ultimate 70 (Van Alstine Modded Dynaco ST70 PCB kit).
    I'm also going to pit it against my Conrad Johnson MV60 (EL34/6CA7) tube power amp.

    [​IMG]

     
    timind likes this.
  8. indy mike

    indy mike Forum Pest

    Mullard EL-34s and GZ-34 rectifier, David Hafler mentioned in an interview in Vacuum Tube Valley that the Sylvania 7199 was a lower noise choice than the RCA 7199 (I’ve seen both brands with Dynaco labeling so those may have been whoever had adequate on hand stock for a bulk order or had the best price when Dynaco called for pricing).
     
    timind likes this.
  9. BIGGER Dave

    BIGGER Dave Forum Resident

    Ah! Two of my favorite tubes! The Mullard EL34 (XF2) and the Mullard GZ34 (built to last a lifetime, or two!).
     
  10. indy mike

    indy mike Forum Pest

    They are dandy tubes that last a long time in the ST-70. :cool:
     
  11. jhenry

    jhenry Well-Known Member

    Location:
    United States
    I’m demoing the new Dynaco ST70 and it sounds really good. Output seems higher than the rated wattage, drives my Vienna Mozarts nicely. I’m using a Mytek Brooklyn DAC+ as the preamp. Not sure about $3000, but I think dealers will be able to discount reasonably.
     

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