"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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    To clarify, if I measure 45 °C at the top of the transformer cover I may infer the top of the transformer inside is 65 °C?
    If the transformer is rated at 80 °C then there is 15 °C margin.
    All this assumes stationary conditions, including room ambient temperature which for me is typically 19 ~ 23 °C.
     
  2. Zampotech

    Zampotech Friend

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    I measured it with a thermocouple. Your measurements will most likely be more accurate than my measurements. I and other SW51 owners will be grateful for your measurements.
     
  3. Zampotech

    Zampotech Friend

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    Yes, this is so under the condition of natural air convection, without drafts and the operation of the amplifier for about 2 hours. This ratio is valid in the medium temperature regime. At a higher temperature, the temperature difference between the transformer and the hood may be greater.
     
  4. Elnrik

    Elnrik Super Friendly

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    So, I usually put my SW51+ in the oven to warm it up before listening. Only for a short duration though, about 20 min. Should I use a temperature lower than 150°C, or is that a good temp?

    I switched over to some Philips EF184s for now. I find they are really close to the 805S sound, but obviously they run cooler. I think I'll stick with these until more about the 805 develops.

    A quick question @Zampotech - is production finished for good, or will more 51's be available in the future? I've been asked by several people about that, several of them looking to buy mine if another run isn't in the future. (I keep saying it's not for sale...)

    (Yes, I'm joking about warming the amp in the oven.)

    ((That's what microwaves are for.))
     
  5. atomicbob

    atomicbob dScope Yoda

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    I'd be willing to bet your thermocouple measurements are just as accurate for the points in time measurements were taken.

    If I were going to measure the desired thermal resistance I would likely put a thermocouple on top of the power transformer and another thermocouple on top of the cover vertically aligned to the first thermocouple. The two sensors would be connected to a data logger for tracking warmup time in addition to thermal resistance differential. Another challenge for another day. Too many other projects in the queue at the moment. And then there is the small matter of actually enjoying listening to music using all these wonderful audio components.
     
  6. atomicbob

    atomicbob dScope Yoda

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    You @$$hole :D ... you had me going there until I saw the fine print :D
    I would also suggest more SW51+ be available in the future for others to enjoy.
     
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  7. Zampotech

    Zampotech Friend

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    To be honest, I don't know yet. Our crazy government makes laws non-stop, each of which is crazier than the other. These people need to take pills, not laws.

    For example, one of the adopted laws informs that on October 1, 2021, all payments from abroad fall into the category of " suspicious". If this is the case, then the delivery of products will be difficult and I will need to look for an intermediary company in the United States with the drafting of a contract.

    PS When a leader dies in our country, the ballet "Swan Lake" is broadcast on all television channels. Recently, I have been very fond of ballet and am waiting for this broadcast.

    PPS Sorry. Emotions.
     
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    Last edited: Jul 5, 2021
  8. atomicbob

    atomicbob dScope Yoda

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    @Zampotech in another thread weaknesses were found for a particular amplifier. It measures very well with a load resistor but when presented real world complex impedance it appeared to become unstable. In contrast SW51+ is very stable as can be seen here

    Can commiserate on craziness in government, another type of global pandemic.
     
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  9. insidious meme

    insidious meme Ambivalent Kumquat

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    Very sad that this law has been enacted. This will definitely drive up your costs not only of the SW51, but for the proposed SW4 and SW9 amps that have been brought up earlier. Hopefully you find a reasonable solution.
     
  10. Zampotech

    Zampotech Friend

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    I hope that there will be a way out of this situation. Russia is a country where the strictness of the laws is compensated by the non-mandatory implementation.
     
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  11. Prydz

    Prydz Friend

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    Can you include a bottle of the finest russian vodka with the amplifier? Not free of charge ofc :cool:
     
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  12. Zampotech

    Zampotech Friend

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    I recognize a kindred spirit [​IMG]
    Alcohol is prohibited in parcels. But there is probably a chance to pass customs if pour the contents of the bottle into a flat flask.
    It is better to come to visit and we will be happy to plunge into an alcoholic coma [​IMG]
     
  13. atomicbob

    atomicbob dScope Yoda

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    A week of simple observations.
    Room ambient has been 23 °C
    SW51+ with EF805S top of transformer cover has been 44 °C after warm-up for several hours.
    I can place the inside of my wrist comfortably on the transformer cover without feeling the need to pull away.
    Hand on top cover is no problem at all.
     
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  14. Zampotech

    Zampotech Friend

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    In addition, we should not forget that transformers made in countries with a 50 Hz supply network work 20% more efficiently in countries where the 60 Hz supply network. An 18 watt transformer turns into a transformer with a power of 21.6 watts. Moreover, the increase in power does not require a single gram of additional steel and copper.
    And of course it will heat up less.
    Therefore, in the USA and Canada there is more room for imagination in of rolling tubes
     
  15. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Hand on top is fairly hot for me, don't think I could comfortably do the wrist. My ambient is high 20s though.

    After powering down with the EF805Ses fully warmed up, I hear a clicking/creaking noise as the tubes start to cool down. Haven't noticed this with other tubes.

    Glad I'm getting extra free efficiency here.
     
  16. atomicbob

    atomicbob dScope Yoda

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    An additional 5 °C (9 °F) would change the outcome considerably.

    My recent environment
    23 °C (73 °F) ambient, 44 °C (111 °F) top of transformer

    Estimating yours
    28 °C (82 °F) ambient, 49 °C (120 °F) top of transformer

    I couldn't put my hand comfortably on 49 °C let alone inside of my wrist.

    Now that a new HVAC has been installed, replacing an 18 yo system my ambient will likely return to 20 °C (68 °F)
    Maintaining 20 °C is important for much of my lab equipment at which calibrations were made and for longevity.
     
  17. fraggler

    fraggler A Happy & Busy Life

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  18. bilboda

    bilboda Florida boomer

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    I'm game, maybe get them to someone with a tube tester to match pairs, they could ship out with markup to cover time and cost. Snipe those tubes at 10 euros +- and there would be plenty left over for add'l costs.
     
  19. Pancakes

    Pancakes Friend

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    Got my SW51+ :punk:

    There have been plenty of reviews so I won't bother (my initial observations match the consensus). Just wanted to say the amp comes packed VERY well, build is superb and, the biasing LEDs lighting up the tubes are wonderful eye-candy. From Russia with love indeed. My post is basically a public thanks to Zampo.

    Ваше здоровье @Zampotech
     
  20. 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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