MicroZOTL 2.0 Measurements

Discussion in 'Headphone Amplifier Measurements' started by purr1n, Mar 28, 2016.

  1. purr1n

    purr1n Finding his inner redneck

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    The last thing I want is for people to go full-nwavguy on measurements. That would not be good and cause me to immediately stop doing any sort of measurements for amps and DACs. Still does not mean these measurements have no bearing on perceived sound. Remember, not too tight and not too loose with reading these things. (I've been listening for a few hours now and have taken notes. Will get to subjective impressions later.)


    MicroZOTL 2.0 Measurements.
    Lots of higher harmonics on the single tone tests. The IMD tests are typical for amps with tubes in them.

    1kHz @ ~0.550Vrms (using /10 diff. probe) into 330 ohms
    MZ2 1kHz.png

    3kHz @ ~0.550Vrms (using /10 diff. probe) into 330 ohms
    MZ2 3kHz.png

    60Hz @ ~0.550Vrms (using /10 diff. probe) into 330 ohms
    MZ 60.png

    50Hz and 7000Hz 2:1 into 330 ohms
    MZ2 5-700.png

    600Hz and 1700Hz 1:1 into 330 ohms
    MZ 6-17.png
     
    Last edited: Mar 28, 2016
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  2. chakku

    chakku Friend

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    Damn when I saw you made this thread I was going to jokingly post something about going full nwavguy but you beat me to the punch!

    The harmonics do raise a little concern as a pairing with the HD800S though.
     
  3. purr1n

    purr1n Finding his inner redneck

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    Measurements into 30 ohms

    1kHz @ ~0.550Vrms (using /10 diff. probe) into 30 ohms

    MZ2 30 1kHz.png

    3kHz @ ~0.550Vrms (using /10 diff. probe) into 30 ohms
    MZ2 30 3kHz.png

    60Hz @ ~0.550Vrms (using /10 diff. probe) into 30 ohms
    MZ 30 60.png
     
  4. purr1n

    purr1n Finding his inner redneck

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    There is an odd quality with the treble. I would be concerned even with Audezes (which I am using right now).
     
  5. bazelio

    bazelio Friend

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    I'm starting to feel somewhat vindicated in the HF thread.

    :)
     
  6. purr1n

    purr1n Finding his inner redneck

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    I am posting this for reference. Measurements from the Laconic Night Blues Mini. I not certain of the topology. My guess is push-pull, transformer output for sure. All tubes, transformer output. The ZOTL is tubes, with ZOTL output. The ZOTL circuit takes the place of the OPT. Uses a high frequency carrier with transformers, MOSFETs, etc.

    As we can see, less higher order distortions with the single tone signals, note no forth order. Could it be the higher order distortions and some of the odd order distortions causing the "difficult" (glassy, strident, fatiguing) treble on the MicroZOTL 2.0? FWIW, the Laconic is a much smoother sounding in the treble, not any different from a traditional tube amp. Also, the second harmonic is significantly lower on the Laconic compared to the MicroZOTL.

    Laconic Night Blues Mini
    1kHz @ ~0.550Vrms (using /10 diff. probe) into 330 ohms
    NBM 1k.png


    3kHz @ ~0.550Vrms (using /10 diff. probe) into 330 ohms
    NBM 3k.png

    60Hz @ ~0.550Vrms (using /10 diff. probe) into 330 ohms
    NBM 60.png

    As expected, the Laconic, being coupled with a transformer (non exotic costing $$$), starts to struggle a bit in the bass.
     
    Last edited: Mar 28, 2016
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  7. bazelio

    bazelio Friend

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    I guess I'm in need of a "measurements for dummies" guide, but am I somewhat correct in interpreting the ZOTL results vs the Laconic results as: The ZOTL seems to have transients of significantly greater magnitude but a smaller static gradient in the higher frequency range? Also I guess you skipped the 4 kHz tone for the Laconic?
     
  8. purr1n

    purr1n Finding his inner redneck

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    I just added a few more measurements. This is purely distortion having nothing to do with transients. Harmonic distortion is composed of multiples of the signal which should not be there. In fact, anything other than the signal being fed be should not be there. There are some small contributions from the DAC, power supply, HE lightning, but they are minuscule compared to errors committed by amps.

    It's often thought that higher harmonics, especially odd harmonics, sound bad and are the cause of the nasty kind of solid-state sound.
     
  9. purr1n

    purr1n Finding his inner redneck

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    Here is Vali 2 for comparison. 1kHz into 330ohms / high gain. Comparable second order distortion to ZOTL, but so much cleaner the rest of the way.
    [​IMG]
     
  10. hifi01170

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    Thanks @purrin for the measurements!

    would changing the stock tubes improve the distortion measurements to a significant extent?
    I am myself the owner of this amp, and the glassy treble is indeed bothersome.
    So I'm just wondering now if it is an inherent design issue that can never be overcome with tube rolling ?
     
  11. Jun

    Jun Friend

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    My inner nwavguy might take the Vali2 instead. I am not liking the odd higher order harmonics. I think linear tube audio should ship you the new power supply so you can measure it.
     
    Last edited: Mar 29, 2016
  12. zerodeefex

    zerodeefex Grumpiest admin

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    Measurements look pretty good on the vali 2. How is the sound in comparison?
     
  13. bazelio

    bazelio Friend

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    Thanks @purrin . -EDIT- OK, I was confused about the test method too. You are only injecting a single 1 kHz tone, and the rest of it is all distortion. Holy shmikey!

    It'd be interesting to see the same measurements with a different tube complement and any LPS ... because at least to my ears they combine to calm down that treble distortion... though it's still noticeable to a lesser degree on some tracks.
     
    Last edited: Mar 29, 2016
  14. Serious

    Serious Inquisitive Frequency Response Plot

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    Yes
     
  15. purr1n

    purr1n Finding his inner redneck

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    Nope. One of the mysteries of measurements. Tubes may sound different, but as long as they are functioning and up to spec, these types of measurements will stay the same.

    I swapped tubes last night to some good 6SN7s which I know are laid back sounding... I thought I had hit the jackpot - you know how it is - everytime you change something, it MUST be better! After more extended listening, I realized the treble still had that glassy strident fatiguing property. I'm leaving the unit on to bake to see if this changes things.

    I'd rather not say that this point. I need more time. Ultimately they have a little bit of a different sound. Maybe Satanic heptagon later? Ask me again after I get subjective impressions together.
     
    Last edited: Mar 29, 2016
  16. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I can't speak for the MicroZOTL, but I know someone tested a bunch of tubes on the Crack and did find some differences with distortion and frequency response extremes. No massive changes, i.e. it's not like the Crack all of a sudden went down to 0.002% distortion.
     
  17. schiit

    schiit SchiitHead

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    Tubes do change the distortion measurements, even within the same type.

    An example: the best tubes for distortion measurements of the 6BZ7 variety are the ones we're currently shipping (RCA Canada). A close second is the JAN GEs we had for a while. The problem is, when you're buying 10K-20K NOS tubes at a time, you don't have a lot of choice as to what's available, so what we ship varies. Though the RCA Canada tubes should keep us rolling for at least a year or two.

    Although the measurements vary, I can't say that it correlates highly to sonics, though (at least not in "higher distortion = bad," in that kind of way.) The tubes do sound different.

    NOS tubes also vary in terms of noise--and this can be highly variable. The JAN GEs were great. We throw out about 5% of the RCAs. The 6N1Ps (used in Valhalla) are also great--and they also match very, very closely. Russian tubes are usually very tightly matched, quiet, and dead-reliable.

    New production tube measurements aren't bad (distortion-wise), but we've found them to be more highly variable and more subject to early death (usually by becoming noisy). That's why we avoid them.
     
  18. purr1n

    purr1n Finding his inner redneck

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    That's good to know. I'll recheck again. On the new production tubes... explains why a pair of EH I had ended up noisy. I kept scratching my head on that one.
     
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  19. bazelio

    bazelio Friend

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    I would think if you consider only a single variable like microphonics, then a swap from a microphonic to a non-microphonic sample would necessarily be reflected in the comparative measurement of those two tubes in the same amp... and presumably there are many other variables. Clearly I'm no tube expert.
     
  20. purr1n

    purr1n Finding his inner redneck

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    It's a lot of work to nail down the variables! Definitely a topic of interest though.
     

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