Amplifier on tubes "Bachelor"

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Zampotech, Oct 9, 2019.

  1. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    @Zampotech Could you provide more details how this compares, from an engineering and design standpoint, to the NBM/ZDT Jr and Shortest Way?

    I know you were going for a lower cost SET amp, but I'm curious about the more technical info. I want to figure out what its place is among those other amps, and not necessarily just from a cost or size perspective.

    Thanks!
     
  2. Zampotech

    Zampotech Friend

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    This amplifier circuit uses successful solutions from three amplifiers. It is based on the sw51 amplifier. There are also circuit solutions from NBM and phonopreampT15B.
    In addition, the amplifier uses a power transformer from SW51 and a slightly modified output transformer from NBM (in my opinion - this is a good transformer). The tube is a cheap and fairly linear 6Z1P.

    First impression - this amp has more bass than my NBM. But first of all, I don't have a sharp analytical ear, and secondly, I haven't listened to it long enough.

    I have not yet fully explored the possibilities and not yet fully measured this amplifier.

    After the measures are completed I can provide the SBAF community with this amplifier for analysis and criticism

    If you agree, I will send this amplifier to you.
     
  3. MisterRogers

    MisterRogers Ethernet Nervosa

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    Oh sure, @Hands ALWAYS gets to play with the new stuff. Jeez. Just because he can hear a cricket fart... :)

    @Zampotech - that'd be awesome. We're working on scheduling a CO crew meet for Feb. It'd be great if it could arrive by then (but no worries if not). Earliest meet date would be Feb. 15th.
     
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  4. Zampotech

    Zampotech Friend

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    Thank you for reporting the meeting. Now I'll hurry

    This amplifier does not yet have an exact name. The name "Bachelor" causes rejection in the wives of married men. I'm afraid to use it
     
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  5. Dzerh

    Dzerh Friend

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    I don't think many significant others care enough about the hobby to know amp names :)
    Or you can rename it to "Bachelorette" to stay in the trend :)
     
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  6. Zampotech

    Zampotech Friend

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    Male logic is based on two elements "Yes" and " No". Female logic on three, "Yes", " No " and " May be"

    Therefore, the name "Bachelorette" certainly will not cause rejection, but real rage [​IMG]
     
  7. Sqveak

    Sqveak Friend

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    @Zampotech what is the gain?
    If the gain isn't too brutal than this could make a nice amp for sensitive biocellulose dynamics.
    The low Z out also looks promising for the Verum 1.
     
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  8. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Well, it's no problem if you can't make that timeline.

    I would be more than happy to test it out or whatever else you need. While I think getting it to our upcoming meet would be very interesting, otherwise don't feel obligated to have me be that first tester. Plenty of other great listeners here. :)
     
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  9. Zampotech

    Zampotech Friend

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    Amplifier gain 6 dB (l output) and 12 dB (h output)
    I think the gain is a bit excessive, I will change to 4/8 dB

    Addition: I measured the potential of "Bachelor" when working on a load of 8 ohms. At the output L, the amplifier is able to give 50 mW. Current through headphones approximately 70 mA
    I don't know if it's a lot or a little. I don't have "Verum-1" headphones

    Edit 2. As far as I know, here on the forum sometimes there is a designer of headphones "Verum". He might be able to answer some of the questions if he was given the raw data.
     
    Last edited: Jan 8, 2020
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  10. Dzerh

    Dzerh Friend

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    Verum1 needs 200 mW at 8 Ohms according to @Garuspik.
     
  11. Garuspik

    Garuspik Tovarisch Ukrainian Terminator MOT - Verum

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    50 [email protected] ohm? ;( Apple dongle is more powerful.
     
  12. Zampotech

    Zampotech Friend

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    no doubt. In class D, there is no particular problem to get more power.

    The result was found out. This is a poorly compatible pair.
     
    Last edited: Jan 8, 2020
  13. atomicbob

    atomicbob dScope Yoda

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    Geez, some of you listen VERY LOUD!
    According to published specifications Verum 1 sensitivity is 96 dB/mW with nominal impedance 8 ohms.
    50mW would result in 113 dB SPL. Allowing for 10 dB peak to average that still is 103 dB average with peaks hitting 113 dB SPL. Waaaaay too high SPL for any length of time in a listening session.
     
  14. Zampotech

    Zampotech Friend

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    probably the answer can be obtained after full-scale tests. I will pass the amplifier @Hands, perhaps at your meeting there will be an opportunity to rape the as much as possible this amplifier.
     
  15. atomicbob

    atomicbob dScope Yoda

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    If this amplifier makes it my way I will run my standard suite of measurements suitable for posting.
     
  16. Dzerh

    Dzerh Friend

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    may be better to do it not for first iteration. As there is probability for changes after suggestions based on listening first demo unit.
     
  17. Zampotech

    Zampotech Friend

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    Before sending @Hands , I improved the amp a bit.
    It was necessary to measure it. I don't have the perfect measuring equipment like @atomicbob
    I had to follow the path of a poor engineer.
    I bought a vintage DELL industrial computer for about $8. This computer is completely shielded, and it is also slow, so it has very little interference of its own. It had a sound card that was as old as mamoth shit. But everything works.

    The "SpectraPlus" program was downloaded to this ancient computer

    Here is the result of self-testing the sound card noise

    [​IMG]

    The result was quite decent

    Then I measured the amplifier's own noise

    [​IMG]

    I took measurements during the day, in a room where other powerfulequipment was working, but my ears in the headphones did not hear any noise or hum.


    THD measurement result of the sound card generator

    [​IMG]

    Now the main result, the THD of the amplifier (The beginning of the graph has been changed for ease of reading)

    [​IMG]

    Of course, my measurements are difficult to call accurate measurements, but the overall nature of this amplifier is already visible.

    EDIT. Added the THD graph of the sound card generator.

    PS: Side effect. During the measurements, the amplitude spikes were detected at the Schumann resonances
    This doesn't apply to audio equipment, it's just interesting.
     
    Last edited: Jan 15, 2020
  18. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    @Zampotech At what level, and what sort of load, did you take those measurements?
     
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  19. Zampotech

    Zampotech Friend

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    You asked a very good question. Sorry, I should have reported this earlier.

    The measuring signal was removed from the Low output. The load was included in the High output. The load value is 36 ohms.
    The output level measured by a calibrated analog voltmeter was -10.5 dB.
    [​IMG]
    The volume value for the ultrasone 580 headphones (32 ohms) at this level was "Very loud"
    I wanted to measure the amp at a higher level, but unfortunately the sound card gets overloaded quickly. I need to make a transition device for measuring a wide range of levels. But at the time of measurement I don't have it yet

    Addition: maximum possible measurement for my simplest measurement system.

    [​IMG]

    The sound card input is enabled via a 1:5 divider. Level output Low +0,5 dB, the load of 36 ohms.

    When the level is increased further, the sound card generator stops forming a pure sine wave.
     
    Last edited: Jan 16, 2020
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  20. atomicbob

    atomicbob dScope Yoda

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    Question: was the amplifier operating 0 dB gain input to output?

    Making that assumption and looking at the meter display it appears distortion measurements are at 237 mV or -10.3 dBu. This is a very reasonable maximum operating level for many headphones which will produce between 90 ~ 100 dB SPL. Your ultrasone 580 have a sensitivity of 101 dB SPL at 1 KHz and 32 ohms. At -10 dBu they will be producing approximately 104 dB SPL which is VERY LOUD as you have noted. Please don't listen to that very long for sake of your auditory health.

    Another note. It appears you allowed 1.87 dB headroom for your measurement, very wise. Maximum output of your DAC before sine clipping is indicated at approximately -8.43 dBu or 294 mV. Now 294 mV translates to -10.6 dBV which lines up with consumer reference level of -10 dBV. For comparison pro audio levels reference +4 dBu.

    Here is a chart you might find useful. This is from my lab where we want to achieve the same apparent sound level across a number of headphones. It is derived from a combination of 1 KHz and Pink Noise measurements on a dummy head with lab microphones as well as Pink Noise listening comparisons for level matching.

    20191128 headphone sensitivity voltages cal 94dBSPL=-16dBFS v2.png
     
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