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

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

  1. yotacowboy

    yotacowboy McRibs Kind of Guy

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    The (claimed by reputable seller, nostubestore.com) early production tubes I received have older looking boxes and slightly different printing.

    Early tube with date code (I'm assuming 1967 based on TCTubes info, but who knows?):
    [​IMG]

    Top of early tube:
    [​IMG]

    Early tube box:
    [​IMG]
    More early tube box:
    [​IMG]

    Later tube:
    [​IMG]

    Later tube date code (that I can't fully make out, but both of my later tubes have a '5' year code, and I'm assuming 1975):
    [​IMG]
     
  2. Merrick

    Merrick A lidless ear

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    I do like those B&W boxes but it wasn’t worth paying more for it.

    By the way, anyone else notice nostubestore has raised their prices on these? I believe we did a run on their inventory. Glad I grabbed two pair!
     
  3. fraggler

    fraggler A Happy & Busy Life

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    Worth $50ish for a pair as an upgrade to stock? My amp hasn't shipped (though I think I am in this batch), but I don't want to miss out on a consensus upgrade.
     
  4. Merrick

    Merrick A lidless ear

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    IMO yes. They do a very nice job of minimizing the SW’s flaws while maximizing its strengths. Given that the NOS prices are still reasonable on these tubes, I’d grab some now.
     
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  5. dllmsch

    dllmsch Friend

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  6. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    Just a note to be careful when you buy your tele... I picked up a set of "Tele" EF184 on ebay months ago. They came in the color tele boxes, still wrapped in old yellowed plastic (obviously never opened), printing was old tele, except no diamond on the bottom and a Siemens tube code (ie., with the ≠ symbol in the code)... they ended up sounding meh.

    I'm going to give these a try...
     
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  7. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Doh, of course they couldn't be '55s. Don't know what caused that brain fart.

    I asked Koray at nostubestore:
    Who knows who's right? But I was born in '65 so it's nice to think these tubes are the same age as I am.

    Left a pair in running overnight and will listen more today. They definitely have much less gain than the Mullards, at least 1 "tick" on the SW51's volume knob. I think part of the initial strong impression of space at the same volume setting was the reduced levels making things sound farther away. They still sound more spacious than the Mullards, have a bit more macrodynamics, and are more engaging (YVMV, new toy syndrome, expectation bias, etc.).
     
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  8. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Doh, replied before seeing the posts below @Biodegraded's.

    Your older ones do look an older style than mine, which look like your later ones. I guess I got '75s (checking again with Koray).

    Currently says $15/$33, which is what I paid.
    http://www.nostubestore.com/2012/01/telefunken-ef805s.html


    Update: I showed Koray @yotacowboy's post and:
    So even more confusing? Fuggit, imma just listen to music ...
     
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    Last edited: Jul 2, 2021
  9. Merrick

    Merrick A lidless ear

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    Did you specifically purchase the older dated tubes? When I purchased it was older production ones (B&W box) for $15 each or $33 for a matched pair, and $12 each or $27 for a matched pair of the newer production (full color box). Now it looks like only newer production is available but at the $15/$33 prices.
     
  10. gixxerwimp

    gixxerwimp Professional tricycle rider

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    No, I didn't think at all about the production dates, and he told me he shipped those when I asked after the fact.

    Not sure how @yotacowboy got '50s production when there was only supposed to be 60s and 70s ¯\_(ツ)_/¯
     
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  11. atomicbob

    atomicbob dScope Yoda

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    what could be better than an SW51+?

    How about two SW51+ ... one equipped with Mullard EF184, the other with Telefunken EF805S
    IMG_2895_small.jpg

    Will be listening to these two amps while documenting much data collected on several DACs and a few other interesting items.

    many thanks to @yotacowboy , @gixxerwimp, @FlySweep and others for pointing out the merits of EF805S.
     
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  12. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Well that was fast! Where did you get yours? And what year are they supposed to be?
     
  13. Walderstorn

    Walderstorn Friend

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    Curious about this tube comparison. Where did you get the tubes from?
     
  14. dllmsch

    dllmsch Friend

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    Besides the gain being lowered, does anyone with EF805S find that the centre block of the amp getting warmer as well? I wonder if it's gonna shorten the lifespan of the amp.
     
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  15. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Yes, I noticed this too! But wasn't sure if I was remembering correctly.

    Surface temp on the top of the front center block* is in the high 40s C (measured with a very cheap thermometer placed on top of it). I let it cool down a bit and put the Mullards back in. After running for a while it only gets up to just below above 40C.

    Calling @Zampotech ...


    *Edit: I believe it's the power transformer under there. So I guess the EF805S draws more current?
     
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    Last edited: Jul 3, 2021
  16. Elnrik

    Elnrik Super Friendly

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    I noticed this heat difference as well, by touch. I'm a little concerned. Let us know what he says please.
     
  17. atomicbob

    atomicbob dScope Yoda

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    the tubes were acquired from the same vendor as @gixxerwimp , Kory at http://www.nostubestore.com/
    They arrived within days, amazingly. Level matching is exemplary as demonstrated further down this post.

    Decoding the numbers on the Telefunken EF184 it appears they are from 1961 and 1965.
    SW51+ #2 L channel : U3001506B
    SW51+ #2 R channel: U9005608J

    IMG_2900_small_adj.jpg
    Mullard EF184 in left SW51+ and Telefunken EF805S in the right SW51+
    The picture in the previous post still had the Amperex 6EJ8/EF184 in SW51+ on the left side of the picture.

    FLIR0298.jpg
    Temperatures look reasonably similar between the two amps.
    Detailed information in the next post.

    Gain matching

    Left SW51+ with Mullard EF184 - approximately 0.4 dB difference between L and R channels
    20210703 SW51+ Mullard EF184 channel gain match.png

    Telefunken EF805S are matched to within 0.06 dB between L and R channels
    20210703 SW51+ Telefunken EF184 channel gain match.png

    When setting amp levels for unity gain I observed the Telefunken EF805S had 4.5 dB less gain than the Mullard EF184.
     
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  18. atomicbob

    atomicbob dScope Yoda

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    Temperatures were observed after 1 hour warmup for both amps.
    Room ambient temperature was 21 °C

    Mullard EF184 on Left, Telefunken EF805S on Right for laptop viewing
    Mullard EF184 on Top, Telefunken EF805S on Bottom for phone viewing

    Front of power transformer cover
    FLIR0289.jpg FLIR0294.jpg

    Top of power transformer cover
    FLIR0291.jpg FLIR0295.jpg

    Left side tube
    FLIR0292.jpg FLIR0296.jpg

    Right side tube
    FLIR0293.jpg FLIR0297.jpg

    It appears the transformer in the amp with EF805S tubes has an elevated temperature of approximately 7 °C over the amp with EF184 tubes. EF805S tubes also have elevated temperatures. Nothing here to cause me any concern at this time. Will watch over several hours.
     
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    Last edited: Jul 3, 2021
  19. Walderstorn

    Walderstorn Friend

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    I was actually going to say that in the first picture the left amp looked a few degrees cooler than the right one. 7 is kind of a big difference, even if it doesn't affect the function, or am I wrong?

    I have had hotter (one of those something rbesr from ebay and didn't have any problems, at least with temperatures. Sound-wise it was a different story.
     
  20. atomicbob

    atomicbob dScope Yoda

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    I'm not too concerned until the temperature reaches 45 ~ 50 °C.
    Then focus on the thermal design becomes more important.
    I should measure the Bottlehead Crack transformer temperature.
    When I get the EC Studio B setup again I'll also check it.

    *edit*

    I should point out my ambient is 21 °C. If it were 30 °C I might be hesitant to turn on ANY tube amp.
     
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    Last edited: Jul 3, 2021

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