Unfortunately what I require I can not buy pre-fabricated. But I did try standard cables, they did not fare any better. they are bulky, and I also would need a USB-C OTG dongle, which makes the whole contraption way too big.
The situation is when I put the phone in full plane mode (all transmitters off) the effect goes away, am I imagining it? don't think so. when the phone is transmitting, different cables make a difference. I have made a few, two are pictured below.
The one with just a simple ferrite cylinder makes a tiny improvement, the other with two multi-turn ferrites (one for ground, another for 5V) has made the largest improvement. phone on plane mode has the highest effect.
Headphone is a Hifiman Sundara, which sounds pretty good with phone on plane mode and the better cable.
I do not have that option with a phone, but a PC optical sounds same as phone on plane mode with the better USB cable - but only to my ears, and not in a quick A/B test.
Lastly may I thank my lucky stars, that I can get answers from designer of my equipment, this is really rare! and appreciated.
Thank you
@Rob Watts for taking the time at 7am to reply.
This last week has been very busy, so I have a lot of replies to catch up on.
So if you can hear a difference between flight mode on/off, then that does suggest it is RF induced current loops. Which is not something I have experienced with Mojo - I can't say I have ever noticed a difference with flight mode on or off. My mobile sounds the same all the time. It's also puzzling to think of an explanation too; for current to flow, we need a physical loop, so phone>mojo>headphones>phone for current to flow. And of course there is no electrical connection from headphones to the phone (apart from electromagnetic and parasitic coupling capacitance).
What you might like to try is as short a USB cable as possible - and to keep the headphone cable well away from the phone and USB cable. Once I was listening to different USB cables, and was getting inconsistent results - sometimes it would sound different, sometimes the same. It turned out to be the dressing of the cables - it needs to be exactly placed so that the USB cable comes no where near the OP cables. I sharply coil up unused USB cable lengths, to minimise the possibility of this type of interaction. It's also possible that the headphone cable is influencing things too; try screened headphone cables. Perhaps the headphone itself could interact with the phone, and influence the sound quality.
When connecting a source to a Qutest via spdif, would you recommended the source be grounded?
Thank you for your very informative posts
It may make a difference - try it and see. If it's warmer, smoother or darker then keep it grounded; if it's brighter then remove the ground!
That's quite a statement.
Absolutely. But I can only report on what I hear and the technical reasons for it. That said, YMMV! But USB cables can only change the sound by influencing the random RF noise levels; so a brighter sound is definitely a degradation; and people are unwittingly increasing RF noise in order to make it appear to sound more transparent - but it's simply more noise floor modulation from the random RF noise.
@Rob Watts What about leakage currents with un-grounded USB source that is SMPS powered ?
For Mojo and Hugo2, which don't feature USB galvanic iso.
That's not really a problem, as it's mostly 100/120 Hz, plus switching noise at typically 50kHz. It's the random noise above 1MHz that is the real problem, and that is suppressed in a quality SMPS.
If I place my old iPhone too close to the Mojo, and cellular is on, I get a faint Morse code like noise intermittently, especially if the phone shows 1-2 bars and less often if it is showing 5 bars. If I move the phone further away (because my cable is long enough) the noise is gone. I wonder if you can try the same. My assumption was that with older phones and weak signal, the phone ramps up the power so much that it generates too much EMI/RFI in the surrounding air that the casing of the Mojo cannot block. In my case, the noise didn’t have anything to do with the USB cable. But it’s always possible your situation is different than mine.
That sounds like GSM buzz from 2G - and it's actually 220Hz or thereabouts, it's not RF. This problem is rapidly disappearing, as 3/4/5G don't suffer from it as the transmission is continuous and not the burst mode of 2G. Turning the phone's RF transmitters on and off creates large low frequency currents, and it's this 220Hz surges that creates the buzz.
Any recommendations (brands/stores) for good quality certified USB cables?
thanks!
No - I happen to use a gold plated generic one, that uses ferrites on both ends, and I sharply coil unused cable. But it sounds the same as a bog standard certified cable. I don't know where I picked it up from.
Yesterday I was trying out some Disney + with Nvidia Shield (full million taps) + MDave and I thought the sound quality is horrible.
This may also vary from country to country, but I used the english original and it is with every other movie too
I don’t want to bash Disney here, the movie (Alita) was great but I was wondering why everything sounds so grainy and hard, every musicality was sucked out.
This seems to vary a lot by the streaming service. What is it that makes these drastic changes?
Observations so far are that some services (on Netflix it also changes with each movie/series) have almost bluray quality, while others sound very aggressive.
My ranking of the sound quality would be like this: Joyn (low budget german series app) > Netflix > Amazon Prime > Youtube > Disney.
I really don’t want to bash any service here I just hope that I am just missing something that could improve the quality, because at this point Disney is almost unwatchable because of this.
Am I missing some important setting in the apps here, like an high quality stereo stream….setting on the TV/Nvidia Shield…VPN service (good quality maybe in UK/US Stream)?
Hope this is not to far of topic…it is still related to extracting musicality with the mscaler anyways…
Disney+ can sound good - I am thinking of Mandalorian here. But I agree, Netflix consistently sounds better than all the other streamers. I read that Netflix has a higher data rate for it's audio, with their own audio compression. I haven't heard poor streaming sound aggressive though - poorer sound quality sounds soft and too warm (compression here degrading transient accuracy) and poorer depth.
But the Nvidia Shield with the full 1M taps is a big improvement. I am so happy that a poster recommended it.
Sorry, but this is not my experience. I did listening test between one generic usb and three audiophile cables. One low cost (supra), one midprice brand A and one high price brand B.
Brand A and generic sounded clearly worse. Supra and brand b was very close, supra sounding a little darker and being much cheaper I bought supra.
To the story is also that brand A had some technical flaw and could not support full usb bandwidth as a data cable. While both supra and brand B worked perfectly as data cables.
Maybe there are generic usb that sound good, but not every generic sound good. But this can be due to that they are not to spec.
I can only report on my experiences - and each cable and source is different. Some sources USB sounds identical to optical (optical is the reference) some sources it doesn't.
But the guiding principle is that a warmer/darker/smoother sound is the more accurate one, if it's less impressive superficially - but you will be rewarded with musicality and lack of listening fatigue from the warmer sound.
@Rob Watts,
I’ve been listening to Apple Music, now that Apple bought Primephonic and have added a catalogue of high bitrate lossless classical albums. I eagerly await their promised dedicated classical music app.
I have noticed that the bitrate LED colour on the HMS does not change appropriately when listening to a playlist of tracks with differing bitrates. To be clear I will explain 2 situations.
When fast forwarding to the next track in the playlist, the LED changes to the appropriate colour for the bitrate as noted on the Apple Music app. There is also a static sound between tracks, which you previously stated would happen unless the track is actually stopped and the next one started.
But when letting the playlist play through the end of the track and automatically start the next track, the LED does not change colour. Nor is there any static, which to me would indicate there is no bitrate change. This occurs whether the first track is 192/24 going to 44.1/24, in which case the LED remains Blue for the 44.1/24 track, or vice versa, where the LED would remain Red for the 192/24 track.
Do you think that this is an error with the HMS or Apple Music? Or am I missing something else?
Thanks,
Fed
The M Scaler (and any of my DACs) can and will only report the incoming data rate (that's why I put it on). So it's the app that's the problem here.
Hi
@Rob Watts
Have you seen optical isolators that can be used for USB interfaces, like this features? The guy zooms in to the isolators.
Is optical isolation of USB input something you're looking to eventually implement in future products?
So all the desktop DAC's and M scaler has galvanic isolators built into USB, with the USB decoding chip isolated too. So the DAC receives a I2S type signal, so the FPGA has no processing to do to extract the data. And of course the clock comes from the FPGA, so no source jitter is possible.
The isolator I use is faster than optical isolators, with better skew, and has similar coupling capacitance to optical isolators. It's the coupling capacitance that is the key here, as this will determine how effective the isolation is. I also employ RF filters and ferrites, to reduce the effect of the 2pF coupling capacitance across the isolator.
Which makes it strange that one can still sometimes hear differences between optical and USB - and the reason is that the ear/brain is incredibly sensitive to tiny amounts of noise floor modulation - if there is any trace of it, no matter how small, it's audible.
