GS-X Mk2 Amp

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by velvetx, Oct 15, 2015.

  1. cooperpwc

    cooperpwc Friend

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  2. TMoney

    TMoney Shits on SBAF over at Head-Case to be cool

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    What a great review! If I wasn't about to take delivery on something else this amp would be next in line.
     
  3. M3NTAL

    M3NTAL Friend

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    @Tyll Hertsens - In future amplifier measurements, can you measure the amps at each of their gain settings to see if this has any affect on any of the measurements? I've read that the Pico Power sounds like crud at low gain and excels at high gain. My personal experience with that amp does not agree with that, but it is always interesting to put these theories to the powers of measurement.

    Also - "Technical" is misspelled in your first sentence.

    Thank you!
     
  4. Thenewerguy009

    Thenewerguy009 Friend

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  5. cooperpwc

    cooperpwc Friend

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    I am wondering this too. :) Anyway I already have a good 15 foot Black Dragon balanced cable for my HD800. I cannot bring myself to buy an expensive replacement headphone that also forces the purchase of superfluous too-short cables. Still I would love to try the HD800S.
     
  6. jeeperbge

    jeeperbge Rando

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    How's this amp with HEK v2? I see some have mentioned good synergy withHEK v1.
     
  7. purr1n

    purr1n Finding his inner redneck

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    For HEK V1 and it's splashy treble timbre, I would have some concerns on synergy. GSX2 is best with darker or rolled cans IMO. Lower gain settings might help since HEK is fairly efficient. However lower gain setting is less lively. Have not heard V2, but from what is seems, it's a stabilized V1 without the huge V1 variances in sound. (some V1's were awfully lean and bright).
     
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    Last edited: May 3, 2017
  8. M3NTAL

    M3NTAL Friend

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    @Marvey - I'm not sure if this is the correct place to ask this, but I have seen you and ZD say similar things about the gain setting on Headamp products. Do you think this is something that you could explore in the future and possibly show with measurements with matched levels and load or possibly give us a theory about it?
     
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  9. purr1n

    purr1n Finding his inner redneck

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    This is something that has a tendency to be true across the board and has to do with negative feedback loops and gain. Similar observations have been made by others with the Ragnarok (I believe the loop is localized between voltage gain and output stage, two of the three) and Jotunheim (global I believe). Jason can correct me if I am wrong on the topology. The extent of these tendencies (more lively more open, but more glare and grain at higher gain - vs.- and less lively, more muted, more closed, but better treble behaved, and better bass control at lower gain) tend to be greater on some amps (GSX2, the old HeadRoom big unit stuff) than other amps (Jotunheim, Rag, small unit HeadRoom stuff). Seems to be that stuff that is more stable and good at open gain exhibits less change (or actually just never sounds "SS" nasty), but I am really stretching here - I don't have not enough experience and data points to make this point unequivocally.

    As for measurements, lower gain, more feedback (and more boring, closed, but controlled sound) always results in better measurements for distortion and bandwidth. Go figure.

    It's funny you mention this because Craig and I have been tuning the feedback on the Af amp the past few days, down to the fraction of a db. Not too loose and not too tight, as I like to say. Applies to everything in life.
     
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  10. cskippy

    cskippy Creamy warmpoo

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    Hehehe perfect!

    I thought I was crazy preferring low gain with brighter headphones such as HE-6, but couldn't quite put my observations into words. You nailed it.
     
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  11. purr1n

    purr1n Finding his inner redneck

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    It's subtle, or maybe I should say it really isn't subtle, but rather something a normal person would not expect. I'm really shocked more owners of of certain amps where the gain really changes the sound haven't noticed it.
     
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  12. a44100Hz

    a44100Hz Friend

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    I'm coming around to thinking I prefer low gain for the Schiit SS or hybrid amps; high generally has moar slam but is more fatiguing. This explains why. Cool beans.
     
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  13. purr1n

    purr1n Finding his inner redneck

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    You could try turning up the bias on the Jot. Not going to go there. Don't even ask.
     
  14. MrTeaRex

    MrTeaRex His head's not fat, he's my brother!

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    I'll second that. I greatly preferred low gain with a GSX2, but not my BHA-1, and thought that I was either crazy or it was just the particular GSX2 I heard. (The fact that the BHA-1 "Low" gain option isn't really that low is also probably a factor.) Glad to know it's not just me. It also helps explain why combining the GSX2 and HD800 can make your ears bleed.
     
  15. ultrabike

    ultrabike Measurbator - Admin

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    One observation is that many amps employing operational amplifiers (and perhaps transistors) can become more prone to instability as the gain is dialed up (depending on the load - including the headphone cable and crazy headphone impedance), depending on implementation.

    Furthermore, it turns out that the higher the gain in some of these topologies, the lower the available current feedback for distortion (error) correction. This is one reason many designs use a unit gain stable non-inverting current buffer at the output of the amplifier using unit gain (maximum current feedback with stable operation), as in the case of some two or more stage local feedback amplifiers. This provides quite a bit of current feedback for correction when dealing with difficult loads at the output of the current buffer, while making it easy on the gain stage since the current buffer provides it a relatively easy load.

    Difficult loads in general tend to be "low" as in less than say 600 ohms, but even that may be too difficult w/o a current buffer, depending on the design.

    An example would be the unity gain CMoy that NwAvGuy found well behaved, but started to degrade as he increased the gain from unity to say 3 or 6 dB (can't remember). Then came the O2 which is a two stage local feedback design which to some extent addresses this issue, but suffers from other issues.

    Note not all designs behave this way. Some designs, like multi-stage global feedback, are only stable when the gain is higher than unity. I suspect the HP-1 from @tomchr behaves stellar at gains larger than unity, but may have a rough time if modified to work under unity gain (basically a current buffer mode) conditions.

    On top of all that, many multi-stage global feedback designs use discretes (gain stage transistor arrangements or op-amps) that are not unity gain stable themselves, and need special care when integrated into the overall design. Local feedback designs tend to use stuff that is unity gain stable. But one can still end up with an unstable system.

    So, in a nutshell, lower gain can result in lower distortion and a larger range of loads with stable operation with some designs that rely on feedback for proper operation. Wrong or right, that's how I currently understand it. Is this the case for the GS-X MKII amp? I dunno.
     
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    Last edited: May 3, 2017
  16. ultrabike

    ultrabike Measurbator - Admin

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    All that stuff being said, and w/o generalizing (since I have not heard critically everything and my preferences do not necessarily represent everyones), the GS-X MKII amp did not work with HD-800s for me. It did well with HD-600s, but meet impressions folks.

    One can blame the GS-X MKII amp, or the HD-800 cans, or the source, or the mastering. Whatever, the combo did not work for me. Too bright. And yes, I'm not an HD-800 fan either. Too analytic for me. Mods help, but not enough for me. If HD-800s is a must and they are staying on your can stable, consider other amps if you have similar issues. If low gain works, low gain works.
     
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  17. ogodei

    ogodei Headphone Heaven Gatekeeper

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    It leaves the HEKv2 a little light and loose in the bass, I've heard it better elsewhere. On everything else the can remains as airy, spacious, precise, and fast as I've ever heard it. Soundstage gets even wider, if thats possible. Treble seems pushed a little more, midrange is OK but nothing amazing, comparitively. This is balanced power with the gain on low BTW.

    Overall the synergy is nothing special, I would look elsewhere if you want better base performance and presence on the HEKs but I wouldn't dump the amp because of it ;)
     
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  18. Rotijon

    Rotijon Friend

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    Just got a decent offer on one of these, how do they work as pre amps? Since i dont actually own headphones now, but the option will be nice.
     
  19. cskippy

    cskippy Creamy warmpoo

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    I'm not sure about sound quality, but wouldn't a Freya make more sense? I mean, remote control volume, balanced I/O tubes, passive, JFET? All for less than half of a GSX Mk2?
     
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  20. Armaegis

    Armaegis Friend

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    The best opamp example I can think of is the OPA627 vs 637, about as "boutique" as you could get at the time years ago for ICs before going discrete and I think hovered around the $30/each mark. The 637 was supposed to have better specs, but required a gain of 5x while the 627 was good down to unity (don't quote me on the numbers, I'm going by memory). I think it was possible to get the 637 below five, but required some fancy wrangling beyond your typical DIY'ers ability.

    I seem to recall the AD8397 was another finagly beast, often prone to oscillation if you didn't get the gain structure right.
     
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