Preamp based on the Pass 1.7

Discussion in 'Preamps' started by Peter, Nov 16, 2018.

  1. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    I just bravely ordered this bad boy:

    [​IMG]

    "This peamp line refers to the the famous PASS 1.7, the chassis uses all-aluminum high-end chassis, the knob is a solid aluminum knob, 10MM thick panel, 5MM thick rear plate, 4MM thick side plate, 3MM thick upper and lower plates. High-grade double-sided thick gold-plated PCB, two-channel design on the same PCB, but the two channels of power and ground are completely separate, left and right channels independent of a 40W advanced R-type transformer, to ensure the separation of the left and right channels. All the boards are equipped with new IRF FETs (IRF610/9610), military 718 factory resistors , Panasonic pin electrolysis, and Bennick YONTEX electrodeless MKP coupling capacitors."

    It is in transit now but I will report once I have it in my hands. It is for use between my Oppo Udp-205 and a power amp.

    Does anyone have this preamp, and if so, what do you think?
     
  2. murray

    murray Friend

    Friend
    Joined:
    Sep 29, 2015
    Likes Received:
    390
    Trophy Points:
    63
    Location:
    N.Z.
    The volume control is very close to the transformer. What type is it? A conventional potentiometer/stepped attenuator or a digital encoder to drive a controller-based attenuator?
     
  3. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    I believe it is more sophisticated than you think. That is not the actual volume control, it does control the volume in a sense, but the volume is controlled by relays and resistors on the circuit board.

    [​IMG]
     
  4. murray

    murray Friend

    Friend
    Joined:
    Sep 29, 2015
    Likes Received:
    390
    Trophy Points:
    63
    Location:
    N.Z.
    Oh, OK. That’s what I meant by “digital encoder”. Not a problem if the audio is not going near it.
     
  5. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    Well, it arrived yesterday, but I have not had much time to get to know it yet. I have not even got the cable I have ordered for it yet so I have not been able to take full advantage of the balanced in and output.

    Anyway, I connected it to the single ended output of my Oppo UDP-205, which I use as a dac and then used it's XLR out to feed my power amp. The initial impression is of liveliness, dynamics and transparency. It does not however have enough attenuation to allow me to use the fixed output level of my Oppo, 100. With the Oppo output at 100, then even the lowest possible volume setting is quite loud. To solve this the Oppo can be turned down to 50 or so, or in line attenuators could be installed, something like this https://www.bhphotovideo.com/c/prod...echnica_AT8202_AT8202_In_Line_Attenuator.html. The Oppo will have to be turned down until further notice. I suspect that this issue will be even worse once I start using the XLR out from the Oppo. I believe that has twice the power of the dingle ended output, oh well...

    Why did I get this preamp? Who don't I just plug the Oppo straight into my power amp and use the Oppo's variable output to control the volume? Well essentially i usually play music at quite low levels and therefore must use quite large digital attenuation. By adding this preamp I wanted to cut down on digital attenuation and use analog instead.

    For some discussion regarding analog versus digital attenuation see this article for example: https://6moons.com/audioreview_articles/kinki5/

    I am over all quite happy. the unit has a little mechanical hum, nothing you hear through the speakers. it is very well built, was well packaged and arrived undamaged.
     
  6. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    I am finding it very enjoyable, dynamic, insightful and downright pleasant to listen to.

    Front:
    [​IMG]

    Business end:
    [​IMG]

    System:
    [​IMG]image uploader
     
    • Like / Agree Like / Agree x 2
    • List
  7. rlow

    rlow A happy woofer

    Friend
    Joined:
    Jul 18, 2017
    Likes Received:
    5,838
    Trophy Points:
    113
    Location:
    Canada
    If you’re having to turn down the Oppo to 50 or less still, aren’t you still doing a ton of digital attenuation, affecting resolution?

    By the way, how much did that “bad boy” cost?
     
  8. yotacowboy

    yotacowboy McRibs Kind of Guy

    Friend
    Joined:
    Feb 23, 2016
    Likes Received:
    5,682
    Trophy Points:
    113
    Location:
    NOVA
    Home Page:
    • Like / Agree Like / Agree x 1
    • List
  9. rlow

    rlow A happy woofer

    Friend
    Joined:
    Jul 18, 2017
    Likes Received:
    5,838
    Trophy Points:
    113
    Location:
    Canada
    Thanks. Just read some details around Sabre DAC digital volume control as well. Claims of better than analog volume control with no bit depth loss...hmmm. I wonder if others around here, more knowledgeable in this area, would agree.
     
  10. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    I would not know. Somehow I just like the sound better with the preamp controlling the volume.
     
  11. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    I got it for $526.40 including shipping.

    I think the digital attenuation is not affecting resolution very much, if at all. Somehow the sound just seems more alive with this preamp between my Oppo and the power amp so I feel it is worth having it. I just ordered these to help with the level matching: http://www.ekmpowershop16.com/ekmps/shops/rothwellaudio/balanced-in-line-attenuators-3-p.asp

    I have had the opposite experience. I once owned an excellent Sony CD player from their ES line, built like a battleship. Anyway, I used an Electrocompaniet EC4R "high performance" preamp with it, this "bad boy".

    [​IMG]

    I could use this preamp, or just feed my power amp directly from the Sony CD player using it's variable, analog volume controlled output. It was clear that the Electocompaniet sounded significantly worse than Sony direct using the variable output. It was so bad, that having the Electrocompanied in the chain sounded as if someone had covered the speakers with a blanket, less dynamics, space and detail. (There seems to be some consensus that while the Electrocompanied power amps are excellent their pre amps are a bit hit and miss...).
     
  12. toddrhodes

    toddrhodes Friend

    Friend
    Joined:
    Sep 13, 2017
    Likes Received:
    574
    Trophy Points:
    93
    Location:
    South Bend, IN
    Very interested in how this goes. I'm looking for a simple, balanced in pre to pair with Yggdrasil and a phono pre, to replace my Odyssey Candela (no balanced in). Don't think I would have the same quirks as OP with a source that has volume control built in. Looks like a nice piece of gear at a great price when eBay does another 15% coupon... Have had my eye on the Kinki pre given it's reviews and featureset, using their monos down the road, but this would be significantly cheaper. Since I need something fairly simple, I'm not hung up on cost.
     
  13. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    I just measured the power consumption. 37 watts.
     
    • Like / Agree Like / Agree x 1
    • List
  14. mocenigo

    mocenigo Acquaintance

    Joined:
    Sep 26, 2017
    Likes Received:
    26
    Trophy Points:
    18
    Location:
    Munich
    What’s your power amp? It looks like one of those Chinese clones as well, maybe the KSA 50 clone if it has XLR. And your speakers? Dynaudio? Which model? Excite X-18?
     
    Last edited: Nov 26, 2018
  15. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    The power amp is apparently based on a Burmester design. I find it fantastic, it drives the Dynaudio X18s very well indeed. It very clearly let's you know what is going on upstream of it. I pretty much agree with the part where it says: "unlimited thrust".

    "Ultra-fast power amplifier line designed by fully symmetrical X-Amp.
    The DC is connected and the audio path is without capacitors.
    High damping coefficient for easy control of any horn.
    5 pairs of three Kennel C2922/A1216 per channel, high current capability.
    The small signal lines and large current lines in the machine are all made of Taiwan Teflon oxygen-free copper wire.
    Adopt one 800w Canada PLITRON Need for Transformer.
    Double---mono design, the separation of the left and right channels is extremely high.
    T7-IV amplification module, using 5 pairs of three-legged tube kings per channel, working in Class A and Class B, with unlimited thrust:"

    https://tinyurl.com/ybaojmar

    This is an even more powerful version. https://tinyurl.com/y8vnkhtr
     
    • Like / Agree Like / Agree x 1
    • List
  16. mocenigo

    mocenigo Acquaintance

    Joined:
    Sep 26, 2017
    Likes Received:
    26
    Trophy Points:
    18
    Location:
    Munich
    Thank you. The links do not work here (!) but I found this

    https://s.click.aliexpress.com/e/bLW1JSZ3

    A lot of people diss ChiFi and it is indeed true that the very cheap stuff can be unreliable (I had a little amp where the switching power supply just died the second time I used it) but they do put some care in the more expensive stuff. And in solid state you get 80% of the sound from the circuit, provided that the components are at least decent.

    Roberto

     
  17. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    ChiFi is a gamble, but at this moment I feel like a winner. This preamp sounds sublime and I have not even got the XLR cable for it so I am still listening to it single ended. I have opened up the case and had a look inside and to me it is a work of art.
     
  18. mocenigo

    mocenigo Acquaintance

    Joined:
    Sep 26, 2017
    Likes Received:
    26
    Trophy Points:
    18
    Location:
    Munich
    The only thing missing is some silicone or some hot melt adhesive to keep all those capacitors in place, like some manufacturers of class D amps do. It seems to be quite a good clone of the Pass Alpha P 1.7 - of which one can find several PCBs around and is a favourite of DIYers.
     
    Last edited: Nov 27, 2018
  19. InsanityOne

    InsanityOne Acquaintance

    Joined:
    Mar 21, 2018
    Likes Received:
    52
    Trophy Points:
    18
    Location:
    Ankeny, Iowa
    This is definitely a very interesting development. I have been looking at these "based on" and "inspired by" pre-amps and power amps on Ebay and Aliexpress for a little while now and I have definitely found a few that look really promising. It is nice to see that they are being honest about the quality.
     
  20. Peter

    Peter Rando

    Joined:
    Jun 19, 2017
    Likes Received:
    17
    Trophy Points:
    8
    Location:
    New Zealand
    I am really loving it. I have been in the camp that no preamp is the best preamp, but no so much anymore. A great discussion on preamps:



    A review of an excellent preamplifier: https://www.stereophile.com/content/ps-audio-bhk-signature-preamplifier

    "The BHK Signature's volume control was not, however, completely silent. At two points on the volume scale—between "23" and "24" and between "52" and "53"—I heard a moderate click from inside the preamp, similar to the sound it makes when a new source is selected."
    Mine does this click at one point on the scale.

    "Furthermore, each 0.5dB step was sometimes accompanied by a soft, short chiff from my speakers. This chiffing varied in volume throughout the listening period: it was noticeable at first, then faded to inaudibility, then returned, then faded again. As I write this, it's just barely audible at a few spots in the volume range with no music playing. I'm thinking this must be one of those tube frailties"
    I have also noticed that with my preamp, but less often as I use it more. I don't think it has has anything to do with tubes on the BHK preamp.

    I have no idea why inserting a component like a preamp in the audio chain can improve the sound and it seems like the great BHK does not know either: "With the preamp in, "the music becomes much more compelling and real," says King in an online video. Even he doesn't understand why: "It all comes down to the more general question, why do things sound the way they do? And that's something we don't have definitive answers for in most cases."

    To me it sounds like my preamp also makes the music more compelling and real and it also has the effect of making listening with the volume turned up more pleasurable.
     
    Last edited: Dec 6, 2018

Share This Page