AMB Gamma 2 DAC (or how NWAVGUY fooled us all)

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by purr1n, Nov 19, 2020 at 12:39 PM.

  1. purr1n

    purr1n Finding his inner redneck

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    Special thanks to @rhythmdevils for taking us back to memory lane. The AMB Gamma 2 DAC was a wonderful sounding DAC during the infancy of headphone audio. It was available as DIY only; however assembled models could easily be found for sale. The DAC uses the old Wolfson chip, which is a good sounding part, but tonally it could sound all other the place. The AMB Gamma 2 DAC implementation has a bold sound with a minimum of digital nasties. The tone was its primary selling point. It was not the most resolving or nuanced sounding DAC however.

    Gamma 2.jpg

    I wanted to showcase this DAC because this is an example of how marketing practices prevailed over engineering. For those who actually thought NWAVGUY was a master engineer, looking to save us all from bad measuring gear by developing the ODAC, there was already one DAC design readily available from his arch-nemesis AMB or Ti Kan with arguably better performance. Those of us who have met Ti Kan know what an outstanding and humble dude he is. If there was any DAC that should have been the ODAC, the AMB Gamma 2 should have been it.

    This isn't member-berries, but rather of how we should learn from the bullshit of the past. Measurements forthcoming.
     
  2. purr1n

    purr1n Finding his inner redneck

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    Here we will compare the AMB Gamma 2 with the ODAC with various measurements (not one). The measurement gear is different. I have an AverLAB. NWAVGUY had a Prizm. Results should be similar, or at least we can get close.

    When I see these measurements, it pisses me off. It pisses me off that NWAVGUY was able to hoodwink so hobbyists and self-aggrandize himself when many others were far more deserving from recognition.

    AMB Gamma 2 -60dbFS
    upload_2020-11-19_12-44-47.png

    ODAC -60dbFS
    [​IMG]
     
  3. purr1n

    purr1n Finding his inner redneck

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    Here's ASR ODAC measurements at full scale 1kHz output (GREEN) as a reference
    upload_2020-11-19_12-53-15.png

    Here are my old ODAC measurements 1kHz at 0dbFS
    Note higher noise floor after normalizing and more grass, but harmonic spikes are similar
    (BTW I am getting lower AC mains than ASR)
    [​IMG]

    Here is AMB Gamma 2
    1kHz at 0dbFS
    Lower second, but higher harmonics are higher. Let's call it a win for the ODAC for this specific measurement.
    upload_2020-11-19_12-57-44.png

    However, let's take a look at more measurements. Music doesn't consist of a 1kHz tone at 0dbFS. Such a tone allows no more digital headroom for any other signal.
     
  4. purr1n

    purr1n Finding his inner redneck

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    However, when we get to lower level signals where actual music lives, oh my... It's not even close.

    AMB Gamma 2
    1kHz at -30dbFS
    upload_2020-11-19_13-0-26.png

    ODAC
    1kHz at -30dbFS
    [​IMG]

    AMB Gamma 2
    1kHz at -40dbFS
    upload_2020-11-19_13-2-13.png

    ODAC
    1kHz at -40dbFS
    [​IMG]
     
    Last edited: Nov 19, 2020 at 1:23 PM
  5. purr1n

    purr1n Finding his inner redneck

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    And remember when NWAVGUY presented himself as sort of a jitter whisperer? AMB spanks his ass here.

    ODAC
    JTEST 24-bit
    [​IMG]

    AMB Gamma 2
    JTEST 24-bit
    upload_2020-11-19_13-19-23.png

    BTW, those sidebands are part of the JTEST signal. There are intentional to trigger or make more evident any real jitter. Note how the ODAC cannot even reproduce the JTEST signal properly.
     
  6. purr1n

    purr1n Finding his inner redneck

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    Moral of the story:
    1. Measurements / objectivism can just as easily be marketed.
    2. No one measurement can tell us the whole story. Usually people will only want to show us or "interpret" the measurements they want us to see, but ignore the rest.
    BTW, the AMB Gamma 2 pre-dated ODAC by years. Years and years.

    upload_2020-11-19_13-27-7.png

    o_O
     
    Last edited: Nov 19, 2020 at 1:30 PM
  7. Armaegis

    Armaegis Friend

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    Did you ever get a gamma3 in house to try?
     
  8. atomicbob

    atomicbob dScope Yoda

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    Don't forget this neat little trick the Odac presents when stimulated with a 0 dBFS square wave.

    Here is the overview response:
    01 20180907 Odac SE 20 Hz sqr 0 dBFS 6 Vpp 10mS div - USB - annotated.png

    The area circled in green above will be zoomed below.

    03 20180907 Odac SE 20 Hz sqr 0 dBFS 6 Vpp 100uS div - USB.png
    Isn't that special?
    Digital filter goes bonkers ratcheting substantially.
    Don't think music signal will present nearly square wave rise or fall times?
    Have a look at a timbale hit from a recording below:
    01 timbale single hit.png
    Let's zoom a selection from the beginning of the timbale hit.
    02 timbale single hit - selection to play.png
    this is the timbale beginning waveform which will be sent to the odac
    03 timbale single hit - selection to play - zoom.png
    Here is what the odac does with the timable hit data it received in the digital data stream.
    04 timbale single hit - Odac 0 dBFS.png
    Zooming in we see the odac making rather nasty modifications to the timbale hit.
    05 timbale single hit - Odac 0 dBFS - zoom.png
    Isn' that lovely. Rail to rail ratcheting. I keep the odac in the lab as one of the negative examples of DAC design.
     
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  9. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    Thanks for doing this @purr1n

    It’s very cool to see objectivist bullshit debunked by objective measurements.

    and agreed about Ti Kan of AMB. I’ve met him at meets long ago and he’s the exact opposite of newavdeuce. Kind, humble, intelligent. Just goes to show how good marketing sways people and how often the honest, no BS people get overlooked because they don’t play the game. It’s a pattern that’s sadly repeated all across the world in all of society.

    Similar factors allowed Kevin Gilmore to convince people that Alex Cavalli’s amps were shit. Alex just didn’t play the game and Kevin Gilmore played it very well.

    Just curious, did you use USB or SPDIF? I’m curious how good the USB is on this.
     
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  10. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    If anyone is interested in hearing this I’ve got a loaner tour setup when Purr1n in done with it.

    you can sign up here
     
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  11. purr1n

    purr1n Finding his inner redneck

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    Going on vacation and will be back in a week. First real vacation since after I got out of the hospital late 2018.
     
  12. strid3r

    strid3r Rando

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    I've been using my gamma 2 for over 10 years now and it's fended off my "upgraditis". Outside of meets, the last direct in-home comparison I've done with this DAC is with the first-gen Schiit Bifrost which I had a hard time hearing a difference with. It was a no-brainer keeping the gamma 2 due a combination of its size, performance and portability.

    It's nice to see it getting some technical attention especially in the context of the whole Nwavguy saga. I admit to being one of the many who bought into his hardware, but ultimately found them lacking in overall sound quality (especially the O2 amp). Thanks for doing this!
     
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  13. M3NTAL

    M3NTAL Friend

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    Gamma2 has been my daily DAC at work for over 10 years also. Its at the front of a 2-Chan setup that is all AV123 stuff. X-Omni's and X-Sub. It's a perfect work setup and would probably be great for anyone getting into affordable 2-Chan.

    The Gamma 2 sound seems to be what I am familiar with growing up and nothing about it really offends me in any way.
     
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  14. ohshitgorillas

    ohshitgorillas Friend

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    It was AMB's designs that convinced me to drop the whole objectivism thing, years ago. I had an ODAC/O2 driving some HD650 when I scored a good trade on a gamma2... around the same time, ojneg lent me his homemade CKK amp. I still peek at AMB designs from time to time, the documentation is truly excellent in how thorough it is.

    I don't see myself ever selling my gamma2. The thing is relatively portable, sounds very respectable, and has features like a swiss army knife. It's great to have around in a pinch. It's also really interesting to see how bad the ODAC measurements look in comparison.
     
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  15. Cspirou

    Cspirou They call me Sparky

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    Ti Kan is one of those DIY guys that's universally loved no matter which forum I've been on*. For NWAVGuy to pick beef with him is kind of shit. I can't tell you how many people just assume an active ground is trash engineering just because NWAvGuy said it.

    *Have no idea about ASR
     
  16. HockeyFan12

    HockeyFan12 Rando

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    I own and like this DAC but don't have a clue about engineering. I remember the ODAC sounded worse.

    This will probably read like trolling, but I swear it's not intended to be. It's just ignorance:

    My friends record sound for film and music (from podcasts to theatrical feature films) and generally the interfaces they use are relatively inexpensive. I think the Sound Devices 744T series is $1000 used and good enough for feature films.

    How do these interfaces compare with dedicated amps and DACs for headphone listening? I figure the designs have to be okay if they're made for professional high end recording and playback. The Apogee Duet 2 sounded good to me with HD650s. (Better than ODAC, at least.) The Sound Devices interfaces I have sound great to me.

    But they are very loud and bassy. Strange choice given they're designed for monitoring mixes.

    Anyway where do these fit in? The Mix Pre D I own sounds great to me but there's a lot of bass and a lot of volume. I've never tried a high end DAC and have no frame of reference.
     
    Last edited: Nov 22, 2020 at 2:03 PM

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