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

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

  1. atomicbob

    atomicbob dScope Yoda

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    Setup equipment:
    Spot check manual data collection
    Type K thermocouple + K-Type adapter + Fluke 189
    Fluke 62 max+

    Automated data collection
    Omega OS136 infrared sensor + picoscope 2205A run as a data logger
    Type K thermocouple + K-Type adapter + Keysight 34465A DMM + BenchVue

    Omega OS136 located 9 cm above transformer cover center. Measurement spot size 1.5 cm.
    Type K thermocouple located inside transformer cover in free air approximately 1 cm below the top surface, between transformer and cover side wall. The thermocouple was slipped into the space through the chassis slot for transformer wires.

    Setup picture:
    IMG_2906_small.jpg

    Automated measurement data
    20210718_SW51+_EF805S_xfmr_top_cover.png

    Spot check manual measurements correlated well with the automated measurements. It should be noted the Fluke 62 max+ measured consistently 2 ~ 3 °C below the Omega OS136 which is within the specified accuracy tolerance.

    Ambient temperature was tightly controlled to 20.8 °C with the new HVAC system.

    It would appear the free air temperature inside the transformer cover is 3 ~ 4 °C higher than the cover top surface.

    My suggestion would be to keep the transformer top cover surface below 46 °C and certainly no higher than 50 °C. Following this suggestion should allow sufficient margin for the transformer core temperature to remain within operating limits.
     
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  2. Pancakes

    Pancakes Friend

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    Which tubes are those (having a hard time identifying them from pic)? Thx.
     
  3. Elnrik

    Elnrik Super Friendly

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    Telefunken EF805S.
     
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  4. Pancakes

    Pancakes Friend

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    Thanks.

    For those with only the crudest of temperature measuring devices (your hand), here is Nelson Pass' temp scale. So don't go above "blimey hot" and you're fine lol.


    Blimey hot is 10 seconds hands on = 45 deg C.

    Crikey hot is 5 seconds = 50 deg C.

    Bloody hot is 2 seconds = 55 deg C.

    X*[email protected]! is 60 deg C.
     
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  5. Zampotech

    Zampotech Friend

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    Everything is relative...:)

    When I was 18-19 years old, I worked at a communication node in the hardware of rectifiers. The communication center was located in the Karakum Desert (this is an approximate analogue of the Nevada desert)
    In the room where the rectifiers were located, the temperature was +70-75 C Outside, the temperature was +55 C
    The ventilation was working, the air conditioners were working, but the temperature was still high.
    The shift on duty had to constantly change the selenium rectifier bridges on the ancient rectifiers, they could not withstand the high temperature and burned with the smell of rotten eggs.
    So, after half an hour of work in the rectifier hall, the street temperature of +55 seemed to us like a cool evening breeze.
     
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  6. Mordy

    Mordy Acquaintance

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    Found a very nice sounding tube - 6F23 (EF812). This tube is made by Mazda, England and comes labelled Mazda or Mullard.
    Not difficult to find nor expensive - it has a beautiful mid range and clarity.
     
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  7. fraggler

    fraggler A Happy & Busy Life

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  8. Erroneous

    Erroneous Friend

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    I tried to snipe them but didn't bid high enough, unfortunately.
     
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  9. Mordy

    Mordy Acquaintance

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    Last edited: Jul 20, 2021
  10. Riotvan

    Riotvan Got lost for three weeks at Delft City Hall

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    So i have one of these bad boys on order and really looking forward to it. However reading back a bit i saw the flir images @atomicbob made of the tubes and it got me worried i need some kind of tube cage.
    The amp is going either inside or on top of a tv/av furniture piece. Problem is my dog can reach those tubes easily with his nose. Probably a learn once never forget type of deal but of course i’d rather avoid that.

    I was thinking of something like two mesh metal pen holders upside down or something. But welcome to ideas.
     
  11. Pancakes

    Pancakes Friend

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    Maybe just plop a couple of these over the tubes?

    https://www.amazon.com/Cary-Guard-P...L5ILK8C/ref=dp_fod_2?pd_rd_i=B00L5ILK8C&psc=1

    Or something similar if those are not available in the Netherlands.
     
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  12. Riotvan

    Riotvan Got lost for three weeks at Delft City Hall

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    Yeah that could work, might still be a bit too hot though? Seeing the tubes reach 148C.
     
  13. atomicbob

    atomicbob dScope Yoda

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    IR measurements are plate temperatures inside the glass. The glass is still very hot, approximately 30 to 35 °C lower than plate temperature, and shouldn't be touched.
     
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  14. Riotvan

    Riotvan Got lost for three weeks at Delft City Hall

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    Thanks! Then i feel more confident in one of those tube protectors.
     
  15. Royaume

    Royaume Rando

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    Any progress on the SW4? I am looking to buy an amp soon, preferably with a 4-pin xlr which the SW51 lacks.
     
  16. superman

    superman Rando

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    Hello @Zampotech and Indian brothers.

    I am superman & just joined this lovely forum. I have HD6xx and I wanted to buy Darkvoice when someone told me that SW is much better than DV. I dont have much money so this will be much end game.

    So, is there any batch to be shipped to India in future? And what will be approximate total price including customs/fees?
     
  17. Zampotech

    Zampotech Friend

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    According to the results of sending 4 and 4+ batches, it will be known how many free amplifiers will remain. Several customers canceled the order for various valid reasons. Now there are 8 amplifiers without owners.

    By price:

    Since April, steel (2.5 times), copper (2 times), technical oxygen (used in laser cutting)have suddenly risen in price. Therefore, for new batches of amplifiers, I will have to recalculate the cost.

    All the amplifiers that were passed in 4 and 4+ batches will remain at the old price of $315.
     
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    Last edited: Aug 2, 2021
  18. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    I'm still amazed at all the performance packed into something so inexpensive. I just shake my head everytime I see the price. :punk::bow::punk:
     
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  19. mdr30

    mdr30 Acquaintance

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    The Telefunken EF805S is certainly an interesting tube with its own qualities, that's my initial impression. Time will tell how it compares to other versions. From what I recall the original Russian tube is hard to beat, but I haven't made a detailed comparison. If a tube sounds good I tend to keep it in for a couple of months or more, and I haven't experienced any inferior-sounding tubes for the SW51. It's a nice all-round amp.

    [​IMG]
     
  20. superman

    superman Rando

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    OK thank you, around 300-350 is my budget also. Is it possible to message me the usernames of few Indian buyers over PM? So that I can talk to some of them regarding custom fees charged to them?

    After talking to them and knowing about the import fees, I will finally be ready to order from you!
     
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