Review - New Dynaco ST-70 Series 3

Discussion in 'Audio Hardware' started by BIGGER Dave, Feb 6, 2019.

  1. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    The friendly FedEx deliverer dropped off a new Dynaco ST-70 Series 3 at my home yesterday. At first glance, the shipping box appeared VERY large for what I'd consider a small/medium sized amp. I opened the shipping box and I find a box-within-a-box. Dynaco double boxed the amp, which is a good thing since there is less of a chance of damage. I opened the second box (which was also oversized) and I find the amp was cocooned in shipping Styrofoam. So far, everything looks good. I removed the plastic bag that covered the amp and the amp was (as expected) pristine. I went ahead and read the entire Owners's Manual before attempting a hookup. Nothing in the Owner's Manual that was unexpected. I placed the amp on top of my bedroom dresser, connected the supplied beefy 14/3 power cord, connected my speakers (Harbeth M30.1), and a source (Sony UBP-X800 BD player into a Schiit Gungnir MB).

    There is no preamp incorporated in the ST-70, so I needed to adjust volume levels by using the TRIM Left/Right controls on the front of the amp. The first disc I played was the Pink Floyd WYWH SACD. Sounded wonderful (as expected), however it was not mastered loud enough to drive the Harbeth's to uncomfortable levels, even with the TRIM controls on '10'. Nevertheless, WYWH sounded better than I've ever heard it and was I excited to try more CD's. Next was Aimee Mann's Ultimate Collection. This is a release that Aimee does not approve of, however I enjoy the song selection and play the disc often. At the first note, this disc was mastered MUCH louder than the WYWH SACD. I had to turn the TRIM controls down to about 60% to equal the volume of WYWH with TRIM controls set to '10'. Aimee's voice sounded holographic at times, more so than with any previous amp I've owned. IMHO, the clarity is amazing for a $1,500 USD amp, and there is a surprising amount of slam from only 35 watts per channel. In the near future I would like to acquire an active preamp so I have better control over the volume, and to potentially drive softer-mastered CD's to louder levels.

    Conclusion - I wasn't sure that I was going to like this amp when I ordered it, however I feel it's the best sounding amp I've ever owned (even with stock JJ tubes!), so I will be keeping it. I have plenty of NOS 12AU7 preamp tubes and NOS EL34 output tubes so it will be fun trying those.

    Product link: Dynaco ST70
    Tube complement: (4) 12AU7/ecc83, (4) EL34/6CA7
    MSRP: $1,499 (previously $2,999)

    [​IMG]
     
  2. G B Kuipers

    G B Kuipers Forum Resident

    Location:
    Netherlands
    Interesting. How does the sound compare to other amps you've tried on your Harbeths? And which amps were they specifically?

    Specifically interested in:
    - frequency extension (both high and low end)
    - colorations or lack thereof
    - dynamic response (are fast transients coming through?)

    Thanks!
     
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  3. JackG

    JackG Forum Resident

    Location:
    NJ
    Nice review, thank you. Does it really say made in Canada? :righton:
     
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  4. loudinny

    loudinny Forum Resident

    Location:
    Northeast
    Circuit boards or all point to point?
     
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  5. rebellovw

    rebellovw Forum Resident

    Location:
    Florida
    awesome - should be pretty nice.
     
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  6. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    My other amps are not high end. They are:
    Marantz 2238B
    Adcom GFA5400
    Crown DC-300A Series II
    Crown PS-400
    Scott 299C

    Out of the Solid State amps, the Crown Ps-400 was most authoritave, but seemed one-dimensional. The Scott 299C was my second favorite (to the Dynaco), however the Harbeths need more watts than the Scott can give, so the nod goes to the Dynaco.

    Frequency Extension - I’m not feeling anything was lacking with the Dynaco. Deeper lows and clearer highs than the Scott, and on par with the more powerful Crown PS-400. The Dynaco came with an indivualized test chart and it tested flat from 10 Hz to 20K Hz, and then is only down by 0.25 dB at 30K. Granted the testing is done at only 1 watt, however I’m not hearing any filtering of the highs (that my 57 year old ears can hear).

    Coloration - compared to my other amps, the Dynaco did not sound any more colored, in fact, I feel the Dynaco may be the least colored compared to any of my other amps.

    Dynamic Response - I feel the Dynaco is fast. The first notes of the Aimee Mann CD came through from black silence and scared me with the amount of slam, which I wasn’t expecting and caught me off guard. Overall, I’m not finding anything to dislike about this amp, and a lot to love!
     
    Last edited: Feb 6, 2019
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  7. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    Yes, on the back it reads:

    dynaco TM
    Made in Canada
    ST-70 Vacuum Tube Stereo Amplifier

    Also, all three transformers are labeled: Made in Canada
     
  8. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    Seattle, WA
    While this amp looks nice, I find it misleading that it is called a Dynaco Stereo 70. No only has dynaco been defunct since the 70s, but this is an entirely different amp than the original

    I'd love to hear one of these though. I was never a fan of the original stereo 70 as anything other than a platform for building a new amp on. But if this amp already has a good circuit, then rebuilding becomea unnecessary.
     
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  9. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    PCB, no Point-to-Point. Not sure it would be possible to produce a profitable Point-to-Point stereo EL34 tube amp using Canadian labor for $1,499 USD. Maybe, not sure.

    One more thing, it includes a THREE YEAR TRANSFERABLE LIMITED WARRANTY. Any defects will be remedied free of charge for (3) years from original date of purchase. There is no mention of tubes being excluded however it states, “excludes finish and wear and tear on components under normal use”, which I take to be the tubes are guaranteed not to be DOA, however anything beyond that may be considered wear and tear and may not be warranteed. Not a major concern, as I have plenty of NOS tubes I’m anxious to try, which will most likely put the stock JJ’s on the shelf.
     
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  10. jonwoody

    jonwoody Forum Resident

    Location:
    Washington DC
    I seriously can't believe you

    :D :p

    But seriously congrats on your new amp it looks great and sounds like a winner. Perhaps try pairing it with an active preamp you may even gain more sound quality.
     
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  11. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    Seattle, WA
    What does that switch on the front panel do? From the picture it looks like it allows you to roll-off your bass or something. But I can't imagine why anyone would want to do that.

    And does the manual contain a schematic?
     
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  12. juno6000

    juno6000 Forum Resident

    Location:
    Pembroke Pines, FL
    Can this also use 6L6 tubes or variants like 7581A?
     
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  13. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    An explanation can be found on the website - “Due to the extended low frequency response, the improved power supply, and the inherently lower damping factor the tube amplifier provides, operation with acoustic suspension speakers may result in an exaggerated low frequency response. Hence a high pass, 3 position filter switch is provided with a bypass position and two different cut-off frequencies that gently roll off excessive bass with a gentle 6dB per octave slope. This not only accentuates low mid punch, but helps reduce neighbour listening fatigue when the amp is played loud!”

    No schematic was included with the amp.

    Read more here - Dynaco
     
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  14. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    Seattle, WA
    My understanding is that 6L6 variants are not especially fond-of running in ultra-linear mode in the first place, and that 6L6 variants are at their best when running in true Pentode mode. I also believe that the (original) dynaco iron was specially optimized by Hafler for the very best possible ultralinear operation when used with EL34s.
     
    Last edited: Feb 6, 2019
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  15. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    I do not believe so.
     
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  16. rebellovw

    rebellovw Forum Resident

    Location:
    Florida
    How about some beautiful glowing tube pictures from your house?
     
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  17. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    I hear you. Anyone with enough cash can probably buy a dormant name and try to put out a product on the laurels of past glory. But the new Dynaco ST-70 at least comes from a company with some experience in Hi-Fi and pro-audio. Dynaco is now under the Radial Engineering of Canada umbrella. Pro musicians are probably familiar with Radial bass guitar / keyboard direct boxes and guitar effect pedals. Radial also produces Primacoustic acoustic panels, Jensen transformers and Hafler Pro Audio products such as phono preamps, headphone amps and power amps.

    Here is an in-depth discussion on the development of the new ST-70 Series 3 -> Dynaco
     
    Last edited: Feb 7, 2019
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  18. captwillard

    captwillard Forum Resident

    Location:
    Nashville
    How does that matter?
     
  19. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    Seattle, WA
    It probably doesn't to most people.

    However, some people think that point to point sounds better than does PCB construction. Also, PCB construction does worse in terms of long term reliability than does PCB construction. And PCBs do not hold-up nearly as well for modders as does point to point construction.
     
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  20. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    Agree with everything you said, except I think you meant to say "...PCB construction does worse in terms of long term reliability than does PTP construction.".

    In some rare instances, a PCB can warp over the long term, especially when subjected to heat from tubes. The warping can cause intermittent connections or even solder breaks. And, modding a PTP amp is easier than attempting to remove/replace caps and resistors on a PCB.
     
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  21. captwillard

    captwillard Forum Resident

    Location:
    Nashville
    I can see point to point being easier to tinker with, but if you look under the hood of most components (from Sony to Boulder and all points inbetween), there is a reason that you see circuit boards...sound, consistency, and reliability.
     
    timind likes this.
  22. TarnishedEars

    TarnishedEars Forum Resident

    Location:
    Seattle, WA
    I'm not arguing against PCB construction here! I'm merely saying that some people think that point to point sounds better. This does not mean that this is my opinion.

    Although I will say that having worked on many tube amps and tube preamps over the years, the ones with PCBs do not take very kindly to being fixed or modified. Circuit foils start to lift and fail very quickly after one or more part extractions from a typical PCB. The same is not true with point to point wiring. OTOH it is a much bigger pain to unwrap leads from posts than it is to pull a component out of a circuit board. So that is one of the downsides of point to point construction.
     
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  23. rebellovw

    rebellovw Forum Resident

    Location:
    Florida
    The only drawback that I've found - mass produced PCBs with embedded components - is the lack of being able to repair them. Nothing at all wrong with a good thick through hole circuit board.

    My amps use thick driver boards (through hole construction) and lots of point to point - very easy to service.
     
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  24. captwillard

    captwillard Forum Resident

    Location:
    Nashville
    Yeah, I'd lake PCB reliability over PCB. For every warped circuit board you have bad solder joints on PTP stuff.
     
  25. BIGGER Dave

    BIGGER Dave Forum Resident Thread Starter

    I think you meant to say "...I'd take PCB reliability over PTP". ;)
     

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