"Shortest Way" 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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  2. Ulises

    Ulises Friend

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    I'd be very interested in getting one if the price and dimensions fall within the ranges stated above. Have been looking for a "pure" compact headphone amp for my bedroom listening setup and would love to try this.
     
  3. Zampotech

    Zampotech Friend

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    The link just selling empty case ;)
    The review of this amp on these links:

    http://zvukomaniya.ru/laconic-night-blues-nb-3a-obzor/
    http://personalaudio.ru/raa/otchety/usiliteli/laconic-night-blues-nb-3a-hi/
    https://reference-audio-analyzer.pro/report/amp/laconic-nb-3a-low.php
     
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  4. Zampotech

    Zampotech Friend

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    Continuation. Today the most difficult part of the case - transformer covers-was manufactured.

    [​IMG]
     
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  5. bilboda

    bilboda Friend

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    In anticipation and because I had expiring ebay bucks, I have 2 Amperex (Holland) tubes coming in. Quite a selection on ebay, Siemens, Bugle Boys, and many others.
     
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  6. Zampotech

    Zampotech Friend

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    Continuation.
    A miracle happened:punk:
    the third version of the transformer completely satisfied all requirements.
    Frequency response 18 Hz - 28 kHz (- 3dB, 120 Ohm load)
    Bass promises to be good, almost to infrasound.:)

    This handsome man:

    [​IMG]
     
    Last edited: Aug 4, 2019
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  7. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    What level is 20Hz at? Is it feasible to get it close to 0dB drop without dramatically increasing cost or size?

    Do you happen to remember the roll off specs for the version I have?

    Oh, and do you have distortion specs for either?
     
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  8. Zampotech

    Zampotech Friend

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    I did not measure accurately at 20 Hz, I have two values at 18 Hz and 25 Hz. If to calculate the frequency response curve, it should be about 2.5..2.7 dB.
    I think the result of 0dB/20Hz will increase the amount of steel in the transformer by about three times.

    Transformers of your version were designed for -3,5 dB/50 Hz (load 100 ohm)

    There is only a mathematical calculation on the current-voltage characteristics of the tube. Is less than 0.1%. But this method of calculation gives a large error both in large and in a smaller way. It is necessary to measure a live amplifier, I certainly will publish it after actual measurements.
    The length of the spectral tail rather than the distortion value will be relevant. For amplifiers on tubes, especially SET, the length of the distortion spectral tail is short and there are mostly even harmonics. Like musical instruments. This provides a natural sound.
     
    Last edited: Aug 4, 2019
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  9. k4rstar

    k4rstar On a journey... somewhere

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    Since the interest in this single stage amp is to drive Senns and ZMF cans what about making a version of this transformer with a single secondary winding optimized for power delivery into a 300 ohm load?
     
  10. Zampotech

    Zampotech Friend

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    Good offer. That's possible
     
  11. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Oh wow, so -3db at 18hz is a big improvement over -3db at 50hz. :)
     
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  12. Phantaminum

    Phantaminum Friend

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    I’m definitely interested in this. Sounds like a perfect amp for the bedroom.
     
  13. msommers

    msommers High on Epipens

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    For the bedroom eh...

    [​IMG]
     
  14. Phantaminum

    Phantaminum Friend

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    You know, when you just want to settle down with a little Marvin Gaye.
     
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  15. Walderstorn

    Walderstorn Friend

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    Maybe a stupid question but couldn't that be sold as an "upgrade"? I understand trying to keep it simple and selling "quantities" to keep cost as low as possible but I had to ask.
     
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  16. Dzerh

    Dzerh Friend

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    Guys, when asking for improvements, please keep in mind this is supposed to be $300 amp, not $3000.
     
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  17. Walderstorn

    Walderstorn Friend

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    Ence being an optional upgrade and not an obligation.
     
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  18. Zampotech

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    Continuation.
    Today completed the construction of the housing of the amplifier

    [​IMG]

    The joins in transformer caps are treated with special heat-resistant putty.

    [​IMG]

    [​IMG]

    A little later, I will work on the improvement and report the result.
    Of course, this will be a separate option.
     
    Last edited: Aug 6, 2019
  19. gixxerwimp

    gixxerwimp Professional tricycle rider

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    So the first photo is of the transformer covers before putty treatment, and the 2nd photo is after application of putty but before sanding (in preparation for painting)?

    Is the putty conductive in order to improve shielding properties? Or just for cosmetic purposes?

    I think this chassis would look really cool in a polished stainless finish! Or even raw stainless with raw welding joints and everything.
     
  20. Zampotech

    Zampotech Friend

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    Putty is applied only for cosmetic purposes. It does not carry any other functions. Only heat-stable patty is used, as the usual polyester putty in the oven (+180 C) is significantly reduced in size.

    A beautiful option, but there are two serious drawbacks.
    1. Joins need to be welded with argon welding. This seriously increases the cost.
    2. The cases can not be touched by hands. On stainless steel remain greasy stains from the fingers, which turn the appearance of the amplifier in the kitchen stove negligent hostess:(

    If the kitchen utensils can be cleaned with aggressive solutions, the body of the amplifier can not be cleaned with such solutions.
    I've tried making stainless steel housings. Was disappointed. The device is suitable only for shop windows, but not for real life.
     
    Last edited: Aug 7, 2019
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