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

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

  1. Benzion

    Benzion "Cogito, ergo sum" Forum Resident Thread Starter

    Brooklyn, NY
  2. russk

    russk Forum Resident

    Syracuse NY
    Definitely be something to give a listen to but my read on it is that they just made the changes necessary to keep production cheap and easy enough e.g. "eliminated troublesome point to point wiring" and ditching the tube rectifier and all those convenient electrolytics. Hopefully it sounds great and hits a price point that makes them successful.
  3. TimB

    TimB Tube be or not Tube be?

    Galion, Ohio USA
    I wonder what the price will be on it? My guess is over $1,000 but I could be wrong. The second generation ST70 was of questionable sound quality, and if I remember correctly had a state state input. Some one back in the 1990's reviewed it and compared it to the original and it was considered less than equal to the original.
  4. Benzion

    Benzion "Cogito, ergo sum" Forum Resident Thread Starter

    Brooklyn, NY
    I can answer that. I asked them about MSRP, and they replied with "$2,999.00" - roughly twice the price of this:

    Ultravalve Vacuum Tube Amplifier , by Audio by Van Alstine, which also claims to be a descendant of the ST-70, but has a more proven track record.
    Kyhl likes this.
  5. Steve Hoffman

    Steve Hoffman Your Host Your Host

    That Van Alstine Ultravalve looks fun. Not much money for 35 tube watts a side. Maybe I'll get one and do a review.

    Edit: Wait, no need, Jeff Dorgay did a review and he loved it. That settles it. Someone get one, it's so cheap!!

    NOS300B, Ghostworld, Manimal and 7 others like this.
  6. chervokas

    chervokas Forum Resident

    No one's heard it yet, so hard to have any opinions. There's probably been more written about the Dynaco ST70 than about any other single piece of hifi gear, and the marketplace is probably have been more full of variations on that circuit than just about anything else on the market over the years from the early Audio Research amp to the Van Alstines to the Sonic Frontiers to the current Bob Latinos, and more mods too with different driver boards and power supply tweaks than you can shake a stick at. Sounds like this new production amp makes some sensible changes -- like beefing up the power supply and power transformer, bias adjustment for each of the output tubes, and in the contemporary era going to a solid state rectifier (you can't get a good new production 5AR4 anyway); sounds like they're also implementing the Van Alstine input bandwidth limiter from my quick reading of the thing. Keeping the original pentode-triode driver circuit will probably please some people and not others -- one of the most common mods is to to replace the old driver circuit. At $3K, that's too much compared to other similar Dynaco variations on the market like not only the Van Alstine but also this one: tubes4hifi amplifier KITs page , or this one if you're a DIYer -- ST-70 KIT (120 VAC)
    Kyhl, SandAndGlass and costerdock like this.
  7. Bill Hart

    Bill Hart Forum Resident

    They need to offer it as a kit! Those were great fun, and very good amps. (Does anyone know what brands of tubes Dynaco supplied back in the day? The transformers were pretty well regarded, I think).
    In doing some cursory research, I saw that Panor? which owned the brand in 2004 rebooted the amp at that time [edit- this date may be wrong]. Never saw or heard one of those. I do remember the early Audio Research modded ones, though. I built mine as a kit and put it to good use driving my original Quads back in the early '70s. Somehow, the retail price of $119 sticks in my mind, but I may be way off. Still have the Quads, can't remember what happened to the Dynaco amp. (I did own an early factory Dynaco 400 that I got as an accommodation when it was first released). Really liked the A-25 speaker, too. What a wonderful part of audio history..
  8. Bill Hart

    Bill Hart Forum Resident

    You and I posted at the same time, Cherv. That Dyna kit at $700 makes more sense to me, given the market niche the original filled.
  9. MATT0404

    MATT0404 Forum Resident

    The original Dynaco branded tubes in my ST-70 were Mullards.
    Bob Y, sushimaster and Bill Hart like this.
  10. libertycaps

    libertycaps Forum Resident

    Portland, OR, USA
    Me 1967 vintage poor man's Macs, Dynaco (not the kits) MK III's, are very dear to my heart....not dear as in insanely expensive, mind.
    Here's to hoping the new production ST70's models are quality and a success!
    Last edited: Apr 22, 2017
  11. psulioninks

    psulioninks Forum Resident

    Kansas City, USA
    I'd like to get one...been thinking about it.
    sushimaster likes this.
  12. Benzion

    Benzion "Cogito, ergo sum" Forum Resident Thread Starter

    Brooklyn, NY
    Me too, I just wish it had triode/ultralinear switch, but it's only ultralinear.

    Brown Audio Labs has this announcement on his front page:

    The SA-70 Stereo Power Amplifier will be available in a couple of weeks, it will be a 35 watt per channel PP, using all Gold Lion tubes, an audiophile grade power supply, available in a silver,black,or white, other customizations available on request."

    Should be coming out "soon", as per Denny Brown's reply to me. According to him, it will have triode/UL switching, and he provided some of the specs:

    Power Output: 40watts RMS, 90watts peak

    Freq. Resp.: 10 to 40,000Hz +/-.5dB

    Power Response: 20 to 20,000Hz at 40watts RMS less than 1% distortion.

    Sensitivity: 1.3v rms for 40watts

    Signal to noise: better than 90dB

    From the name of the amp, I wonder if that is also a re-incarnation of the Dynaco. Overall, I'm intrigued. I will wait for it to come out to see the pricing. If it's acceptable - I might grab one of 'em. If not - Ultravalve is still fun, as our host noted. The new ST-70X - at $3K I want to read what others are saying first, like Stereophile, Abs. Sound, and the usual crowd.
  13. sushimaster

    sushimaster Forum Resident

    The Van Alstine Ultravalve is one of audio's best kept secrets.
    NOS300B, psulioninks and Benzion like this.
  14. Benzion

    Benzion "Cogito, ergo sum" Forum Resident Thread Starter

    Brooklyn, NY
    Are there no worthy substitutes for the 5AR4?
  15. chervokas

    chervokas Forum Resident

    It's just me but strapping pentodes to run 'em as if they were triodes doesn't make that much sense -- with the ST70, when you do that, all you're really getting is half the power and twice the distortion (more than twice the distortion actually if you look at Herb Reichert's measurements for Sound Practices: Triode Connected Pentodes Article By Herb Reichert of Eddy Electronic Inc. Sound Practices Magazine Online ). If you want a low powered triode amp, buy a triode amp. If you want an ultralinear amp, by an ultralinear amp, you'll be better off that way than strapping the ST70 for triode operation.

    FWIW, I have a ST70 that I've rebuilt with the Joe Curcio cascode differential driver circuit and a beefed up power supply including a larger power transformer. It's a good little amp if you don't ask too much of it. I listen to it daily -- it's more like a 30 watt amp than a 35 or 40 watt amp; like most tube amps but especially mid and low powered ones, you need to use it with speakers that have a relatively benign impedance curve relative, it's ideal with a subwoofer amp handling the low frequencies, etc. With this new one, I think $3K is a lot to ask for that considering how many cheaper ST70 variants are out on the market. The Tubes4HiFi is $1300 assembled with tube rectification if that's your thing; the Van Alstine is $1600. At $3K you're in a whole different category. At that price you could go out and by a used 85 watt VTL, or, hell, I just looked online, there's a used audio dealer selling a pair of 300 watt VTL monoblocs for $3,100. At $700 for a kit, at $1K maybe even or $1,500 bucks (even that's getting a little steep), the ST70 is a good choice. But at $3K there are many more choices out there and lots of better ones and ones that will drive more speakers more easily, etc. If you're gonna spend $3K on a tube amp, I'd suggest shopping around widely at that price point before buying a that new ST70.
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  16. chervokas

    chervokas Forum Resident

    I had a a couple of Chinese 5AR4's fail early in spectaular fashion on me. I think New Sensor is making one now so many it's more reliable. I see a lot of the ST70 variants are still using tube rectification (which I'm not wholly sold on as the holy grail in a hifi power amp, who wants sagging dynamic power in a hifi amp?), so the manufacturers must have found a suppler of 5AR4's they're happy with. I rebuilt my ST70 with solid state rectification using high voltage SiC schottky diodes so I can get a freedom from switching noise that approaches tube rectification without the chance of any kind of sag on peak demand.
  17. Ron Scubadiver

    Ron Scubadiver Forum Resident

    Houston TX
    With the Ultravalve @ $1,600 this newcomer doesn't look too exciting @ $3k.
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  18. Bill Hart

    Bill Hart Forum Resident

    I've rolled a bunch of NOS ones in the power supply to my phono stage- at least in that circuit (an Allnic H3000), the tube made a dramatic difference in sound. I like this survey: Dubstep Girl's Massive 5AR4/5R4/5U4G Rectifier Review/Comparison! (Rectifer Tube Rolling thread)
    I guess I should caveat that the electrical characteristics in terms of voltage should be matched. Cherv is right about tube "sag"- good for guitar amps, not so good for hi-fi.
  19. sushimaster

    sushimaster Forum Resident

    For what it's worth, the Mullard is the absolute best sounding and most reliable GZ34.
  20. Bill Hart

    Bill Hart Forum Resident

    I don't disagree, but the sound may be dependent on circuit. I used an early Mullard fat base (the first iteration after the metal based tube) and it sounded great. Most recently, I've been using a NOS GEC U-52, which, at least for the Allnic, is a direct equivalent. It is "airier" than the Mullard, but again, that may be circuit dependent. I agree that the Mullard was a go-to tube--highly regarded in guitar amp circles as well. The early ones are not inexpensive. There is an old RCA that Rockitman (who I think used to post here) raves about--I'd have to look up the particulars-- it is not an expensive tube, compared, say to the Western Electric, which is big money now.
    I bought half a dozen old rectifiers when I got the Allnic, just to experiment. Pretty amazing how much difference the rectifier makes. Thankfully, many NOS ones are still reasonably priced, compared to other tube types.
  21. rl1856

    rl1856 Forum Resident

    They are not making a new ST70. If they did the price point would be much less, because a new modern updated ST70 is available from several sources at about 50% of the proposed cost. They are making a new EL34 based amp, competing with other new EL34 based amps in the market, and looking for a way to differentiate themselves in a crowded market. Someone thought an association with a classic brand name would provide a unique identity.
    trd and Vinyl Archaeologist like this.
  22. chervokas

    chervokas Forum Resident

    Well it does, in the basis of the description, seem to be basically the st70 circuit with some tweeks like solid state rectification, a bigger power transforms, separate pentode and triode driver tubes because the original pentode-triodd driver 7199 tubes aren't in production. Basically it looks like one of many st70 variants out there.
    nm_west likes this.
  23. petercapo

    petercapo New Member

    New England
    Agreed. I tend to think it will appeal to, and reach more of, the non-DIY crowd. For those who know, there doesn't seem much point to it beyond the, Van Alstine and Latino offerings.

    BTW, McShane Design says the newer Tung Sol and Gold Lion 5AR4/GZ34 are solid rectifier tubes. If using the Chinese, JJ or Sovtek, you can put the solid state diodes ahead of the plates to reduce PIV demand.
  24. IanL

    IanL Forum Resident

    Oneonta, NY USA
    The Genalex Gold Lion U77/GZ34 is quite good. I have one of the aforementioned Mullard metal base 5AR4/GZ34 (it is awesome) so I have done extensive comparisons. They are definitely different, and the Mullard will probably outlive me, but the Gold Lion is readily available and about one tenth of the price.
  25. BIGGER Dave

    BIGGER Dave Forum Resident

    The new ST70 Series 3 was announced two years ago. Has anyone purchased one?

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