Today, let's just consider the noise on the +5V USB line from computers:
PicoScope 2204A, he has produced some interesting screen shots to consider with the various machines.
A Look At The Computer USB +5V Noise...
By Raoul Trifan
First, let's have a look at the Lenovo Thinkpad T430 with its multitude of ports:
The next machine is the Thinkpad T440:
Moving along to the next Lenovo machine, this is the old Thinkpad X201 from around 2010:
Surprisingly, the old X201 has the best USB power from all tested laptops in this survey of devices! Again, the docking station seems to show a bit more fluctuation with spikes ~10mV in magnitude but even then you could probably connect your DAC without concern. That right side USB port looks excellent. Quite impressive results from an old device like this one.
Next is a Gigabyte GA-B85M-D3H motherboard used in my desktop machine and the desktop Apple 27" iMac from late 2013:
I’m impressed by the clean USB power from my DIY 4-years-old desktop with the Gigabyte GA-B85M-D3H motherboard when the rear USB ports (soldered onto the motherboard) are used. As for the wired front USB port, please don’t even try using these. Clearly the cheap USB connector and long cable connecting the motherboard to the front of the computer case is picking up noise from inside the case.
Given the audiophile perception (maybe general perception) that Apples are good machines for audio, I was hoping for a cleaner result from the late-2013 iMac, especially since the rear USB ports are soldered directly onto the motherboard (no USB cables involved). It looks like the ripple and noise spikes are not so good!
Despite the spikes from the iMac above, I was unable to hear any issues with the sound itself, but I had no time to do a detailed A/B comparison and have no decent ADC to run RMAA. Anyway, most likely any engineer designing audiophile products seeing the iMac’s USB power waveform above will probably recommend using a good external +5V power supply for the USB or a Y-cable with clean +5V injector.
Next we have a couple of HP notebooks - the Elitebook 2560p and newer 8460p:
The HP 2560p might not having the purest USB power ever, but it’s definitely much better than the bigger brother 8460p! Unlike the Lenovo computers, the HP docking station shows much lower noise level. This just goes to show that I cannot generalize and say that "docking stations are bad" because it obviously depends on the specific device.
As mentioned above, Apple has created quite a following and there are audiophiles who feel that the Macs are better for audio purposes than Windows-based options. To some extent this is understandable given that Macs are often rather quiet sounding machines and aesthetically more pleasing (especially going a few years back). But what about the USB port power noise level? Here are two MacBook Pro laptops:
Finally, let's have a look at a decade-old Fujitsu-Siemens Amilo Pro V3205:
The right side port from my old Amilo Pro is quite decent, too bad the left port is significantly poorer. The rear port sits in between with the amount of noise seen on the scope.
Archimago's Thoughts and Conclusions:
For now, as far as I can tell with my computers, even with inexpensive DACs these days, the power management and filtering is doing a good job without any extra help from audiophile accessories.
I see that the only measurement offered is another FFT of one of 2L's tracks (2L-078). A new "improved" version of the encoding algorithm was done on the music with less noise compared to the DXD playback. So what? The FFT shows that the portion of the track they're demonstrating has no content above 23kHz! So maybe the new encoding may have utilized steeper filters to reduce ultrasonic leakage or maybe they applied lower dithering / noise shaping levels compared to before? Good to see that potential "bug fixing" can be done and there's flexibility in the processing I suppose. However, a simple downsample from DXD to standard 24/48 would have resulted in just as beautiful of an FFT (likely with an even lower FLAC-compressed bitrate)!
The final sentence of the article goes like this (about the "de-blur" and time smear claims):
This smear, we believe, can be material for the human listener who is extracting multiple cross correlations, as well as envelope and nonlinear measures of the audio.I don't understand exactly what Mr. Stuart is claiming here; what "cross correlations" specifically? What "envelope"? Which "nonlinear measures"? Yes, the mechanisms of listening and hearing are complex, but would it not be good to be a little more specific? But the point remains that after all these years (and despite earlier in the article Stuart claims they did "hundreds of experiments"), at best he can say is that he "believes" what they did with MQA was helpful! Surely, out of these hundreds of experiments, he can spare just a little more information about what beneficial evidence they may have found. Given countless opportunities, it's rather clear that they've got nothing. And writers like Jim Austin likewise has nothing to add other than uncritically repeating company claims. At this point, I really hope the McGill University folks have something "material" to talk about (maybe some actual data by the Milan AES in late May?).
If in the days ahead, we see music companies and streaming services actually adopt MQA as a distribution format, I think it's pretty clear that this is in spite of public acceptance of the format rather than what companies would prefer to see - acceptance because of public demand.
This week, we were told that ESS has decided to incorporate MQA "rendering" into their DAC feature set. It looks like they're targeting this for "small and lower power solution" DACs meant for mobile devices and headphone users. Something like the Dragonfly Black rendering on-a-chip. IMO, with actual high performance DAC chips like the ESS 9018 and recent 9038Pro, it's hard to imagine why anyone would want to use those MQA upsampling digital filters on playback as they can only serve to reduce sonic fidelity from these high-end parts.
Anyone getting really tired of MQA yet? :-) I noticed that there was little talk of MQA at the AXPONA 2018 coverage and so far not much from Munich High End (just a couple new partners and their insistence that this represents a "growing momentum"). On the software side, I guess it's finally about time that Audirvana Windows version is released with software MQA decoding; about a year after the Mac. Also, Roon 1.5 now handles MQA including the ability to perform DSP on the unfolded data. Nice to see that MQA is relaxing not only the insistence on achieving "revolutionary" sound quality, but also on how rigidly they're "end-to-end" "authenticating" the playback chain... Yet again, why bother with all the hassle in the first place? I think it is good that Roon has MQA support now given the asking price and the fact that they're closely tied to Tidal. It would be rather unsatisfactory to pay quite a bit for the Roon service and not be able to access the much-hyped Tidal "Masters" feature!
BTW, for those who want something quieter, consider the Cherry MX Brown switches; still feels great with less noise. Also, one could dampen the MX Blue switch noise a little with <$10 O-rings under the key caps which I might do if the wife complains!