Dyna PAS phono stages, my impressions, stock vs Erhart upgrade

Discussion in 'Tube Audio' started by CJVx, Jan 12, 2019 at 8:49 AM.

  1. CJVx

    CJVx AK Subscriber Subscriber

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    I happened to purchase a fully upgraded PAS preamp with the Erhart Audio TCLA tone line amp and jfet PH10 phono stage. I also have a stock PAS3x and have had many of these over time.

    My impressions are that the stock Dyna phono board sounds more natural and “alive” than the upgraded one. The TCLA stage though, is miles ahead of the stock Dyna counterpart. So the best combo I have been running is the turntable into the stock Dyna PAS, and line out to the modified PAS.

    The upgraded PH10 phono board just sounds dead to me. Am I missing something here? I know this company has a great reputation, but I’m very close to install a stock phono board in this hot rod PAS. I use Grado and Shure carts. And the Dyna wins on each. I just want to make sure there might not be anything wrong with the upgrade phono board before I rip it out.
     

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  2. petercapo

    petercapo Well-Known Member

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    The original line stage may sound a lot better depending on the condition of the pots and the associated parts.
     
  3. CJVx

    CJVx AK Subscriber Subscriber

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    The modified PAS was built with new alps volume pot and new balance and tone pots. The filter and loudness switches are not connected so I don’t believe I have any losses through them. The Erhard TCLA line stage sounds brilliantly better than the stock Dyna, but the stock Dyna phono board seems to blow away the Erhard phono board.

    I did just find some jumpers on the Erhard phono board that I don’t know what they do, but some basic listening has shown that without the jumpers, it seems to improve the sound! I measured resistance at the phono inputs and it is 47k with or without the jumpers so again, not sure what they do.
     
    Last edited: Jan 12, 2019 at 6:24 PM
  4. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    I had a tubes4hifi preamp with (what i believe to be ) the same PH10 phonostage. I thought it was pretty bland as well. I think that got spun off. They don't seem to offer it any more.
     
  5. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    I still have a rebuilt (but stock) PAS3X. I think its pretty nice. Honestly there was quite a time lapse between owning both so i can't wager any real comparative info.
     
  6. gadget73

    gadget73 junk junkie Subscriber

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    The PAS phono stage does actually sound quite good if its in proper working shape. Usual stuff, no off resistors, tubes healthy, power supply working like it should, etc.
     
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  7. Lavane

    Lavane AK Subscriber Subscriber

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    I have a PH-10 and the Aikido board I used in a build awhile back. What tubes did you use? I used old stock low noise 6072's. They sounded much better than the EH 12ay7's. also what cartridge are you using? The loading may be off? (Edit) the 47k should be good.
     
    Last edited: Jan 12, 2019 at 9:37 PM
  8. Erhard-Audio

    Erhard-Audio Forums Sponsor Sponsor Subscriber

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    what is the pcb version of the Z-PH10 you are using. If it has the jumpers, it is quite an older version. I'd be happy to send you our current, improved version, Z-PH10v1, free, just pay shipping, what say you?

    DUR...just looked at the photo's!
    Yes, your version is quite old.
    pm me your address, I will send you a new Z-PH10v1 if you're good to pay the shipping charge :)
     
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  9. CJVx

    CJVx AK Subscriber Subscriber

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    OMG amazing, I will definitely take you up on this offer.

    For the record, in my 12AY7 arsenal, I have pairs of the following:
    Pinch grey plate GE 12AY7, best sounding to me
    Pinch grey plate RCA 6072, wasn’t too thrilled
    Pinch grey plate RCA 12AY7, second best
    Box black plate Tung Sol 12AY7, tie with above
    Pinch plate new production EH 12AY7, wasn’t too thrilled either.

    All things can change with the new board, very excited.
     
  10. Erhard-Audio

    Erhard-Audio Forums Sponsor Sponsor Subscriber

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    no probs, you're welcome, just answered your 'pm'
     
  11. tubeactive

    tubeactive AK Subscriber Subscriber

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    Wow ! Serious KUDOS to Erhard ! Exemplary response from a very concerned vendor !

    Before I saw their offer, I was thinking about CJVx's predicament. A near original, but tweaked Dyna PAS RIAA phono stage can measure and sound very nice. The Dynaco choice of coupling caps does stand the test of time, even if the caps are now beyond their "peak" of goodness. They were paper or early mylar film caps. The choice of caps can make definite subjective "differences" even with the same circuit in two similar PAS preamps. Likewise, differing power supply implementations can cause unlike sonics. Tweaking, changing, upgrading or redesigning the RIAA EQ networks can also be causes of differing "opinions" of the resultant sound. Varying tube types themselves, can change character. Newer, metallized coupling caps, wound in a tight, oval shape, will also sound different from paper or later plasticized film and foil type caps. These are but a few factors to consider when evaluating circuitry sonics.

    I checked the vendor sites and reviews, in search of the magical question: Do Erhard retain the active feedback EQ circuitry used by Dyna, albeit with tweaks/upgrades ? Did they add a cathode follower for the RIAA EQ drive or within the upgraded line stage ? Dyna used no cathode followers. Their site or reviews do not reveal their topologies. Alas, maybe we will get some answers within this thread.

    For now, let's all thank Erhard for their sound practices....
     
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