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Hugo M Scaler by Chord Electronics - The Official Thread

Discussion in 'High-end Audio Forum' started by ChordElectronics, Jul 25, 2018.
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  1. Rob Watts
    Before I added the RF isolation treatment on the M scaler outputs, HF GHz clip on ferrites sounded considerably better - warmer sound quality, with better depth and focus. I understand why it works as the problem is down to RF currents (peak problem area is around 2 GHz) flowing in a loop from the mains>Hugo M scaler FPGA ground>galvanic isolated OP>BNC cable> DAC ground plane> back to the mains. It's when the current flowing through the DAC ground plane is where the SQ problems are happening. If we can reduce the value of the currents by increasing the loop impedance then we get less voltage drops across the DAC ground plane and then less correlated noise and lower noise floor modulation. The lower noise floor modulation improves warmth; the reduction in correlated noise (that's noise/distortion that is in the audio bandwidth and is linked to the actual signal) degrades small signal amplitude accuracy, and that degrades the perception of depth.

    It's all very straightforward and well understood - double the loop impedance at 2GHz and currents will half, and we get a corresponding improvement in sound quality - better depth and a warmer sound.

    It doesn't matter too where you increase the loop impedance either; you can do it at the BNC output drivers, or through the cable, or via the PSU on the M scaler, or via the PSU on the DAC - it's the total loop impedance that counts. If the loop impedance is infinite, no current can flow, audio nirvana results. Problem is, at 2GHz even 2pF of capacitance (which is a very small capacitance) is very significant - it is 40 ohms, so will allow current to flow. Moreover, the ear/brain is ultra sensitive to this problem, so the faintest trace of an error is audible.

    So why did adding ferrites improve the SQ? Ferrites work by increasing the common mode impedance, but keeping the differential impedance the same. The wanted signal is differential, the unwanted current is common mode; so adding ferrites increases the loop impedance, without affecting the wanted signal; if you double the number of ferrites, you half the loop currents, thus halving the SQ problem.

    The treatments I put into the M scaler was extensive and aimed at increasing the loop impedance, by improving the galvanic isolation, improving the drivers and the driver PSU, and adding RF filters and chip ferrites into the BNC output ground. In terms of sound quality, I gained about an order of magnitude improvement in SQ - it went from a big problem to a small one. When I then added clip on ferrites it sounded worse - and I was not expecting that. I am not sure of the reason exactly - I suspect a resonance between the internal M scaler ferrites and the clip on ferrites air gap, making the loop impedance lower overall. But solid core ferrites do still improve the SQ - but I should add that it's not a huge difference. When I travel, I don't bother, as it's simply too small a difference and I stick to stock. Compared to the SQ that the M scaler adds, we are talking about the surface finish of the icing on top of the cake - it's the iced cake that's important.

    But remember it's the overall loop impedance that's important, and the PSUs come into this too. If you replace the supplied PSU with linears, apart from breaking the warranty, will degrade the sound quality. This is because linear PSUs have no RF filters - the supplied one comes with input and output RF filters. Also the supplied one has been very carefully selected for no grounding, and very low inter-winding capacitance - many times smaller than toroidal transformers. The lower inter-winding capacitance, together with the RF filters, increase the loop impedance and improve the sound quality. By using a linear will increase noise floor modulation (making it sound brighter, fooling the audiophile into thinking it's more transparent) and increase correlated noise thereby degrading depth (and then the hapless audiophile will then convince themselves into thinking it's better because perceived width is artificially wider due to the poorer depth). Confirmation bias and placebo is a very real problem with listening tests!

    But if you want to almost completely isolate the M scaler from the DAC then use a battery power bank (so long as you site it correctly) - then the loop impedance becomes very high, and then the BNC cables no longer have an impact on SQ as no current can now flow as there is no longer a loop. Is this something I do in practice - no - the difference isn't large enough to bother with charging batteries. At the end of the day I just want to simply enjoy my music more, and I don't need to go to silly lengths to do that.
     
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    pavi, muski, musickid and 22 others like this.
  2. kelly200269
    Cheers Rob, for a very comprehensive, and definitive statement on this matter.
     
    Lgn3 likes this.
  3. gnomen
    Thank you Rob. At last! A very clear and helpful explanation of what is going on and a good cure for months of blundering experimentation.

    So, for those of users who do experience IM distortion - not just the surface of the icing, not just something imagined - what is still going on? In my case the HMS sounded beautiful at an extensive dealer demo but sounds hardened in my domestic setup. What should I do first to get to the state you describe?
     
  4. nomad777
    Clean your power..... if that's out of range.... you can hassel with a BP ...
     
    Last edited: Nov 27, 2019
  5. Lgn3
    Agreed
     
    musickid and kelly200269 like this.
  6. Triode User
    I did not reply directly to your post because I was wary of getting drawn into a situation where others on here, who delight in making mischief, might attempt to bend what I say and allege that I am contradicting what Rob Watts says. I am simply not going to get into that position because it is not true.

    Rob has now kindly posted a full explanation in response to another posters question and hopefully that will also answer your question. You will note that Rob says that although there can be what he regards as subtle ('icing on the cake') improvements due to using battery or solid core ferrites, for him the improvements are of a level that he does not bother with a battery at home or with solid core ferrites when he is traveling.
     
    zenlisten, birdlandbill and Christer like this.
  7. Lgn3
    Thanks for making that clear.
    I think that Rob's last post should have resolved much of the controversy regarding RFI and the MScaler. What he actually said was that solid core ferrites do improve the SQ but that this improvement is not the icing on the cake but we are talking about the surface finish of the icing on top of the cake (emphasis on surface added by me to highlight the difference) Therefore those who wish to purchase a ferrited cable, getting on for 40% of the price of HMS, for such an improvement, may be reassured that they may get one ( assuming everything else in their chain is optimised in such a way as to make this audible ) Others can rest assured that purchasing a pair of well constructed digital cables, available for the price of a HiRes download, can be reassured that they are experiencing 99% of what HMS is capable of and depending on their chain possible 100%.
     
    Last edited: Nov 27, 2019
    Progisus likes this.
  8. adyc
    I would still use battery to power HMS to completely break the ground. Using Chord PSU, I get the tingling feelings when I touch HMS. Although the plug is two prongs, in where I live, neutral is connected to ground. HMS is still connected to earth ground. Another way is to connect Chord PSU to balanced power supply. In this way, neutral is not connected to ground. And I do not get any tingling feelings. It is completely float.
     
  9. nomad777
    Ferrite cable? I only know of one and its ok... nothing spectacular. It's not just the cables its the whole package power source etc..
     
  10. Christer

    Thanks for the response Rob, very interesting to get this in depth information "straight from the horse's mouth" on these hotly debated subjects.

    But if I understand you correctly, YOU like me and obviously others here, DO "go to the silly length" of using solid core ferrited BNC cables at home?
    Correct me if I am wrong...
    But when travelling you get basically the same results as solid core BNC cabling by using the stock BNC cables and a battery pack?

    You recently suggested an alternative battery pack to the PP2 here.
    Have you tried it and can you confirm that it will work as well as the PP2 with an HMS or does your suggestion come only from comparing specs?

    While on the subject of battery power I have recently become too lazy to keep charging and changing between battery power and the supplied SMPS on my Qutest.
    The difference is not always worth the hazzle of having to change unexpectedly in the middle of a piece of music I am enjoying when it happens, so I mostly stay plugged in.
    But as with solid core BNCs over stock BNCs which to me at least, made a VERY notable even,WOW what a difference how is this possible? reaction, in my systems both via headphones and speakers, the battery solution still sounds slightly warmer and fuller than plugged in with the most demanding and really well recorded of my music.
    But with most other recordings the difference is minute enough to be blissfully ignored.
    But I can still hear it via the humble Qutest /HMS combo I am still using with great listening pleasure every day.

    Finalmente, una pregunta mas,
    When can we look forward to a TT2 power digital headphone amp that will work DIRECTLY with the HMS?
    Such a toy would come in very handy for me on my travels and hopefully many others as well.
    If you could hold such in your hands at Canjam Singapore next spring I may even forsake a live concert just to hear it in action.
    Cheers CC
     
    Last edited: Nov 27, 2019
    birdlandbill likes this.
  11. Progisus
    I like how Rob provides a detailed explanation but leaves the tiniest window of doubt. His talent is not only the best dac designer in the world but perhaps speech writing as well!
     
    AndrewH13 and zenlisten like this.
  12. ray-dude
    Alas, when there are no absolutes, there is always a window. Reminds me of the old question of how long is the California coastline? Very different answer if you measure from space vs measuring around each grain of sand on the beach. Depending on how you measure and what scale you measure at, radically different answers to a very simple question. There is still so much to learn about how we perceive sound and the reality around us, so we don't always know what we should be measuring or what scale we need to be measuring against.

    With mScaler, we're all hearing things in recorded music that no one was able to hear before (including Rob). We're going to be hearing (and learning) may new things on the way. For me, aside from the astonishing experience of the music, there is joy and excitement in that process of discovery and the fuzzy truth that is slowly revealing itself. The rewards of tweaking up the icing (and the shine on the icing) far out weigh the hassles (for me). We're all obsessive enough that I appreciate that it may also contribute to FOMO.

    That being said, out of the box, mScaled anything is a world class listening experience that is WAY WAY beyond anything any one would have thought was even possible 10 years ago. For me, a transformational and affirming part of my life that I am immensely thankful for, icing or no.
     
  13. Ragnar-BY
    @Rob Watts thank you so much for explanations!

    I've tried to understand what I hear with different power supplies and made a simple experiment.

    I have Fostex TH-900 headphones, which are relatively sensitive and have quite aggressive sound signature, which unveils even smallest imperfection in recording or gear. My normal listening level with TT2 and these headphones is about -27H for redbook. I took a track with digital silence from Focal Tools CD, out it on loop and started to increase volume until I hear any hiss from headphones. I`ve tried this many times in different conditions, stopping and resuming playback to understand at which point I can hear a hiss.

    I found that with stock PSUs I can`t be completely sure if the playback is active at -15H, and I can clearly hear silent hiss at -10H. With LPSUs (of a very good quality) these numbers are -12H and -6H. At 0H level I clearly hear hiss with both PSUs, but with stock one it is significantly louder. Sure, my ears are not calibrated for measurements, but it is obvious that in my system there is a difference. And I repeated this test for many times. Also, results were similar with optical and USB input of an M Scaler.

    So, maybe loop is not the only problem? Maybe higher power supply reject rate of a good LPSU could bring improvement to sound quality?

    I'm totally on your side that brighter sound is not "better sound" and everybody should remember about "false transparency" feeling of a brighter sound signature. Also, I remember that you told us to look at soundstage depth instead of width. And yes, those PSUs sound darker and soundstage is deeper.
     
    wswbd and ray-dude like this.
  14. Christer
    Oops. I forgot to mention that I would want my new toy to be built max half the size and weight of the HMS.
    Not bigger, please!
    I trust, if anyone, you can do it Rob!
    But it should also be capable of driving any high quality headphone of my choice except maybe electrostatic cans and the RAAL?
    Those are tough.
    And both supercapped and capable of running on a re-chargeable and by me the user/ consumer easily exchangeable battery pack as well.
    Ideally built the way my digital cameras already are.
    When one battery runs out of juice after say 400 exposures, I just stick a fresh one in and keep working.
    I keep three fully charged batteries ready at any time.
    Cheers again CC
     
  15. thePhones
    I could not find anything about this in this thread so I hope that I can inspire some people :D

    Since @Rob Watts has posted about watching movies with the full million taps with Jriver and a negative delay (the audio goes ahead) I was hoping I could find a solution to also watch Netflix with 1 million taps.

    And I am so exited to announce I found it!

    The newest Nvidia Shield TV Pro not just supports Dolby Vision and HDR10 but every model of the Nvidia Shield TV (also the older ones) does support up to 1 second (incremental in 10ms steps) of negative audio delay.
    So far I have testet the app Netflix, Youtube and MKV Movies in "Kodi".
    3D MKV should also work, have not tested it yet.
    Kodi needs some extra work: https://forum.kodi.tv/showthread.php?pid=2698828#pid2698828 (fourth post on the site)
    The audio needs to be routed over the TV or other via HDMI in order to get 48 khz, with USB Android TV is limited to 44.1 (Stereo) or 192khz (Stereo HD)
    So far everything works smoothly with global (android) negative delay set to -700ms and Kodi set to -900ms. Those number may vary a bit depending on your tv set and preference.

    One last tip: To me Netflix audio sounds also less compressed if you have the 4K subscription, so it's worth a try even if you have no 4K TV set.

    Ps.:If you find capitals where they do not belong just know they are from Germany with love :D

    edit: after a bit more testing and comparing the audio quality inside Netflix I have noticed that there seems to be some sort of conversion/compression hapening inside the Nvidia Shield.
    Kodi uses it's own audio driver so to my ears it sounds exactly like playing with Jriver on the laptop without the inconvenience of having to set the laptop up in front of the tv. So the Nvidia Shield is still worth it to me. All my movies are uncompressed as MKV on the hard drive always ready to play connected to the shield.
    I have to do further testing regarding apps that use the android audio driver.

    edit 2: I found the solution to the compression problem. It was caused by an additional app I installed called “refresh rate”. It automatically changes the frame rate and resolution to the played contend. This change in resolution probably told the netflix server that my receiver/connection is not capable of high bitrate.

    So after all everything works now, I’m very happy and the Nvidia Shield TV Pro (2019) is highly recommended. Sorry for the confusion and I hope you are inspired :)
     
    Last edited: Dec 1, 2019
    zenlisten, ZappaMan and Ragnar-BY like this.
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