"Shortest Way" SW51 Amp Impressions (Simple SET Amp)

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Hands, Jul 12, 2019.

  1. gixxerwimp

    gixxerwimp Professional tricycle rider

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    They sound like tone sweeps but at "sub-harmonics" of the fundamental. If it were digital it could be something like Nyquist "ghosts"? Maybe the tubes just need crap to be burned off.
     
    Last edited: Sep 27, 2019
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  2. Zampotech

    Zampotech Friend

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    Rumors about the fragility of the tubes are greatly exaggerated.

    [​IMG]

    In the center of the anti-aircraft projectile-ordinary tube.

    I'm sure because of the exclusivity, the cost of the amplifier on the head-Fi can be even more than you paid for it;)

    I plan to ship out all the remaining amps next week. If PayPal security service does not block the money on the account again for 72 hours.
     
    Last edited: Sep 27, 2019
  3. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I wasn't so much concerned about the tubes being fragile themselves. But if something were to penetrate the box and push hard enough against a tube to bend the pins or even break it, then it would be more difficult to deal with than if it were wrapped and laid flat on its side on top of the socket. However, with Zamp's excellent packing, the chances of that happening are very slim indeed.
     
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  4. bilboda

    bilboda Friend

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    Running the amp thru it's paces, enjoying my modded HD 650's with Roon/HQP and dsd upsampling. Plan to listen to this exclusively for several days, including tv and games. Why? It sounds quite nice right out of the box. After it breaks in a bit, I'll compare against my other amps...
    Shortest way.jpg
     
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  5. Zampotech

    Zampotech Friend

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    Surprisingly. My mail reports that your amplifier is still at JAMAICA NY INTERNATIONAL DISTRIBUTION CENTER

    Mail is faster than its information system
     
  6. bilboda

    bilboda Friend

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    Handed off for final delivery to USPS. It arrived even before the mail. Had a higher than normal Priority sticker on it. Deliver by 3PM. Normal priority usually comes to me after 5 PM making EMS from your shop to my house an excellent choice. Fellow was curious about my shipment from Russia. Imagine if my headphone pads arrived from the Ukraine at that same time. I'd have to pull out the matter of national security card.
     
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  7. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Other than Почта России telling me that my NBM was "Handed over to China for further delivery" in Bejiing after I'd already received it (guess the CCP wants to claim our headphone amps too), tracking and notifications were accurate and timely.

    It occurred to me that the magenta glow at the bottom of the tube might not be coming from the tube itself.
    20190928_090918.jpg

    Seems like there's a light inside the socket shining up into the bottom of the tube.
    20190928_124941.jpg

    @Zampotech is this a functional part of the circuit, or only for cosmetic purposes? If I were to disconnect the LED(?), would the amp still function properly?

    The subharmonic artifacts are very obvious listening to the 22 kHz → 8 kHz Sweep + Voice Over here:
    https://www.audiocheck.net/audiotests_frequencycheckhigh.php

    Oh, and bass is extended and slammin' :punk:
     
    Last edited: Sep 28, 2019
  8. Zampotech

    Zampotech Friend

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    The led is included in the circuit and can not be removed. If it bothers you, cover it with something dark.


    The physics of the origin of distortions in amplifiers is such that distortions on subharmonics can be formed only when the amplifier operates with a signal of two frequencies (intermodulation distortions, ) . The appearance of audible distortions on the subharmonics of only one frequency has nothing to do with the amplifier. The distortion of a single frequency can appear only at the harmonics of
    This rule applies to any amplifier

    Now, until the air molecules are completely absorbed by the gas absorber, you can hear the artifacts. They sound like a crackle and a short hiss. Sometimes as a brief mystical howl, but it is very rare. Howl met only in dual triode type 12AU7
    After a while, the gas absorber will remove the free air molecules and the artifacts will stop.
    Tube almost young, but all-same them more 30 years
     
    Last edited: Sep 28, 2019
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  9. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Thanks for the information.

    I finally decided to try listening to that test tone on another amp and surprise, surpise ... it's there too. So the source seems to be the Bifrost 2, as it's either not or only barely audible using my other DACs. Off to the Bifrost 2 thread ...
     
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  10. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I’ve heard other DACs do that. I don’t think it’s going to affect music playback.
     
  11. bilboda

    bilboda Friend

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    Ignorance is bliss I guess, I have severe hearing loss at 8khz according to the the test on that site and so I don't hear any subharmonics or anything else without a sizeable increase in volume. Amp is still very smooth and clear and detailed after 1 day. I think it would be interesting as a preamp , maybe in a ++ version
     
  12. gixxerwimp

    gixxerwimp Professional tricycle rider

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  13. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Primarily, yes. Old gen Metrum stuff for sure.

    Some NOS DACs measure very, very well. The only thing you’d be able to notice is the treble droop. Most poor measuring NOS DACs come down to the choice of chip, particular output stages (ie could be a zero feedback design, or some bad passive IV solutions), etc. If you get a good chip and make a textbook output stage, it will probably measure quite well. It may or may not exhibit these artifacts.
     
  14. atomicbob

    atomicbob dScope Yoda

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    Very brief expository: SW51 is what the ZDT Jr wants to be when it grows cojones.
    I’m impressed. Very well done @Zampotech !
     
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  15. atomicbob

    atomicbob dScope Yoda

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    A little research on the 6Z51P / 6EJ7 / EF184 tube used by Shortest Way 51 (SW51) and I found this:

    http://www.audiodesignguide.com/New2A3/ETF06TS.pdf

    Look in particular at the blue load line on slide 27. Incredible linearity without use of global negative feedback; see slide 23. Now read the whole presentation.
     
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  16. Zampotech

    Zampotech Friend

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    Yes, colleague, I am also impressed with the merits of this tube.
    There are two other useful practical advantages. It is very weak microphone effect and very good EMI protection.
    Under the influence of this impression, I bought 500 of these tubes (6Z51P) yesterday from an old military depot.
    Of course it's a lot, but sold one lot.
    I'll try them in the Phonopreamp.
     
    Last edited: Sep 29, 2019
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  17. Zampotech

    Zampotech Friend

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    To date, all amplifiers except the last 4 pieces have been shipped.
    Some of them have already been received, some are still on the road.
    Recipients from Europe, please check the track code for the location of your parcels.
    The information system shows me that the amplifiers are at your customs and waiting for your visit.
     
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  18. msommers

    msommers High on Epipens

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    Received mine tonight. House is full-blown renos so impressions TBD against MCTH. Maybe I'll order tubes in the meantime :p
     
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  19. joch

    joch Friend

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    @Zampotech any chance there’ll be another run?
     
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  20. Zampotech

    Zampotech Friend

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    Yes, re-fabrication is possible.
    But there are a few things:
    1. That-would preserve today's the cost of amplifier need circulation not less 20 units. This is the amount when the retail value of transformers, cases turns into a wholesale price. At the same time, I can't make more than 40 amps. I just don't have a place to stay.
    2. On October 1, "Russian Post" reorganized. It used to be state-owned, now it is a joint-stock company. Greedy shareholders raised shipping costs by 17-20%
    3. I'll be busy next week. I was asked to help install and test the radio controls for the cranes. This week can be filled by receiving orders for the amplifier.
    4. Sending a new batch will be possible not earlier than six weeks.


    If this is not frightening, then a new batch of amplifiers is possible.

    PS: I want to wait for independent measurements of this amplifier @atomicbob
    Also, I still have to send 4 more amps to this batch. But it will be decided in the next few days.
     
    Last edited: Oct 6, 2019
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