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Old 14th May 2012, 11:50 PM   #731
Bunpei is offline Bunpei  Japan
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I appreciated barrows' well-organized consideration very much.
How do you feel about applying such a USB High-speed compatible optical isolater to the USB connection between PC and asynchronous DDC device?
SuperSpeed USB 3.0 Over Fiber Optic Expansion System:Amazon:Electronics

Last edited by Bunpei; 14th May 2012 at 11:54 PM.
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Old 15th May 2012, 12:53 AM   #732
wlowes is offline wlowes  Canada
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Default WageIO on VoyageMPD

Quote:
Originally Posted by ENSen View Post
...a Alix board with Voyage mpd as source and for some reason ALSA always mute the WaveIO. When I connected my other DAC it was not muted. To solve this I added the following lines to /etc/rc.local

amixer -c 0 sset 'Luckit Clock Selector',0 100% unmute
amixer -c 0 sset 'Luckit Clock Selector',1 100% unmute

Thought I would post this in case someone else will use ALIX (or other Linux installations) and run into the same problem.
I too use ALIX VoyageMPD. I had the Alsa mute issue on first use (also on Ubuntu). In my case I set mute off using the alsa-util gui. It stayed off without further issue.

I am having a challenge getting MPD DB to update. I tested ALIX with a few WAV files on a USB stick. It remembers the USB but refuses to update with contents of my NAS music folder. It reads the directory and will play, but 2 issues. Only sees about 70% of the tracks, and refuses to update the DB. Anyone else see issues like this? I have RW permissions on NAS directory and other files like .PID and state are being written.

BTW, sound of WaveIO with the ALIX Voyage combo is outstanding. Yes, for some reason OS makes quite a difference. To best of my knowlege I am getting unaltered bit perfect playback on Alix MPD setup.
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Old 15th May 2012, 05:56 AM   #733
rsdio is offline rsdio  United States
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Quote:
Originally Posted by barrows View Post
Consider, that even when supplying a separate power supply for the USB interface, the computer ground is still connected to the WaveIO ground, and hence the computer's ground is connected to the ground of the oscillator's. It is entirely possible (likely) that noise on the computer's ground does raise the jitter level becuase of this connection.
You do realize, I hope, what the term "circuit" means?

Current cannot flow from the computer ground to the separate power supply ground unless there is a circuit - i.e. some other connection between computer and power supply besides ground. You have to connect at least two wires before electricity will flow. Ground loops can cause a problem with ground-referenced signals, but when the ground is the only connection there can't really be a problem.

I'd say that it's nearly impossible (unlikely) that connecting just the ground will cause a problem.

If you dive into the details, the amount of noise will be proportional to the amount of current flowing on the ground. Since the USB power line is open circuited, then 0 A of current is flowing along the power lines. The USB data lines are differential, and ideally referenced to each other instead of ground. If there are any slight errors in the differential matching, there might be some ground current, but the noise level should be much lower than a 500 mA power supply demand from the USB Device.

I suppose there might be something I'm missing, so hopefully someone can explain how connecting ground but not power would conduct noise.
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Old 15th May 2012, 07:44 AM   #734
PET-240 is offline PET-240  Australia
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My thoughts are thus regarding noise. If the smps is generating noise on the USB ground which is present at the end of the ground of the USB cable, since the noise is voltage spikes of varying peaks, the ground at waveio will be a different potential at any point in time. As voltage can be present without current flow, to me it is entirely likely we are getting uA in the ground plane being drained off. The only way to be sure is to disconnect the USB ground at the input and note any differences. Obviously it would need to be connected to the powersupply ground of the wave.
Mine hopefully got posted yesterday so I can't do this yet!

Who's game?

Drew.
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Old 15th May 2012, 08:03 AM   #735
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Quote:
Originally Posted by rsdio View Post
I'd say that it's nearly impossible (unlikely) that connecting just the ground will cause a problem.
But when is a ground a ground? Obviously, dedicating a good PSU to the WaveIO provides it with, by definition, a clean and steady Ground line. Let's assume (reasonably) that the board is laid out to minimise issues with noise on its ground.

However, the Gnd line on a USB cable, far from being rock steady, fluctuates slightly in line with events on the motherboard, something I believe the engineers call "ground bounce". The reference point for the Data+ and Data- lines is Ground, not the +5-volt line or, as you imply, each other. You can usually bypass the USB's +5v line but you cannot bypass the Gnd - the devices don't have to be connected via the USB cable's Gnd (though that's the usual way) but they do have to be connected.

Noise on a USB cable's Ground line tends to disrupt the timing of data. Why that matters with conventional USB audio is fairly clear - the data are read in real time. Why it matters with an asynch device such as the WaveIO is much less clear but it does nevertheless seem to be an issue. (Why it is an issue is discussed in one of the links I cited earlier.)

One reason why an isolator such as the ADuM4160 is effective in the PC Audio context is that it isolates (though, obviously, not completely) the target device from noise on both the 5-volt line and the Ground. But they too need a clean power supply to work at their best.


Quote:
Originally Posted by rsdio View Post
. . . the amount of noise will be proportional to the amount of current flowing on the ground.
It's one variable - but one of many.
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Old 15th May 2012, 11:32 AM   #736
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Quote:
Originally Posted by reo View Post
Do remove the Trident from the Dac's VDD_XO circuit. If you don't have the Trident on your Dac then simply remove the ferite bead that controls the VDD_XO which is located on the underpad (L8)mmm not sure it's that one so follow the trace.... which should disconnect the onboard Crystek .

Now locate your R17 pads on buffaloII ? when looking at the Dac with the twisted pear logos facing upright., you locate the right pad from the 2 R17pads to connect your MCLK live wire only, from WaveIO, then you use the ground wire from your MCLK and connect to left pad of R17 .All your I2S connections from WaveIO to buffaloII will be as short and similar lenght as possible .
hope that helps to synchronize and do convey your results please .
regards
rol
My Wave IO board arrived today - many thanks Lucian, and well done for packing it so well. Looks like someone played football with the parcel...
It's a truly lovely-looking board, almost a shame to put it away in an enclosure.

I'm working out how to wire it to my dual-mono Buffalo II but I'm uncertain how to do this. Is it essential to disable the on-board clocks on the Buffalo as per roll's post above?

I'm going to be using a TP "Teleporter" to send the I2S via CAT6 cabling and something I read from the TP people indicated that you don't need to connect the ground, just use DATA, LRCK and BCLK. I'm a novice at DIY Hi-Fi and I find this I2S connection matter very confusing! All help gratefully received!
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Old 15th May 2012, 11:48 AM   #737
PET-240 is offline PET-240  Australia
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G'day Ryelands,

Query so I understand;

We can disconnect the USB ground and attach a ground from another powersupply, say a shunt reg, does this stop the USB from working? I'm just trying to get a handle on your post. If it does then separating the USB/PC powersupply is much harder(shock!) than I figured. Is the USB ground used to notify the host something is connected? Aside from a data reference you mentioned, what is its purpose?

Thanks muchly!

Drew.
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Old 15th May 2012, 12:33 PM   #738
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The ground in question is the I2S ground between the WaveIO and the DAC. USB ground is unchanged.
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Old 15th May 2012, 01:34 PM   #739
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Quote:
Originally Posted by PET-240 View Post
We can disconnect the USB ground and attach a ground from another power supply . . .
Sorry for the confusion but, emphatically, No. As I understand it, the signal in a USB lead is the difference between D+ and D- referred to ground. No ground? No signal. Normally, the ground line goes from the PSU via who-knows-where to the USB socket on (usually) the back panel down a lead up to five metres long to the attached device. (There's a proper term for attached device but I forget it for now.) The ground line collects interesting things on the way inc noise and significant resistance.

The same goes for the +5v line except that it isn't a reference point for the data signal though, together with the ground line, it often supplies power to the attached device. Crucially, it also almost always tells it that it has a computer attached.

Where the likes of a DAC or similar is attached permanently to a computer dedicated to audio reproduction, we can safely cut the USB's noisy 5v line and obtain a clean, low-noise +5v signal (for signal is all it usually is) either from the DAC's PSU or, for bus-powered devices, from an external PSU. The latter is AFAIK what the AQVOX after-market USB PSU does. Whatever, it's a pretty common tweak that I've done on several systems and IMHO a good one.

Note that if you are in the habit of connecting and disconnecting the DAC while the computer is running, the cable is best left as spec. Also, WRT to rsdio's earlier comment, there is no point whatsoever in doing the tweak to the likes of a disk drive as the data transfers in that case are not real time. So long as the thing works, it works fine.

It was list member wlowes who first gave me the idea of replacing the leads in a USB cable with a couple of CAT5 twisted pairs, one for the D+/D- lines and another for the Gnd and +5v lines. CAT5 is good quality cable, its impedance is pretty close to the USB spec, it can be made nice and short and it's cheap enough even for a Scotsman. wlowes prefers to screen his lead, I leave mine unscreened partly to keep capacitance low but mainly because I'm lazy. (The audible difference from screening that he reports presumably reflects different conditions.)

So in no time we have a USB lead with D+/D- as normal and a Gnd lead but no +5v as that's obtained separately. My "idea" was to try cutting the ground line as well. I got it from a discussion on the AA Computer Audio forum where a "manufacturer" of very expensive USB cables was baffled why omitting the Gnd lead sometimes markedly improved SQ but as often as not wouldn't work at all. I thought the answer pretty damn obvious . . .

In short, if there is another connection between the computer's PSU ground and the DAC's ditto, you can safely cut the USB cable's Gnd lead and perhaps improve SQ. If there isn't, you can't - the link doesn't work.

The Gnd-Gnd connection is provided either accidentally by the likes of safety earth lines or through the back door by your connecting the Gnd line of the two PSUs together at appropriate places. The reference point for the USB's data signal is thus likely to be significantly cleaner than it is with any USB cable no matter how expensive.

I tried the idea successfully on one system and got a definite improvement in SQ. I also tried it on a system using an ADuM4160 isolator where it didn't work but, before I worked out why, I discovered the WaveIO and didn't bother fault finding. When I get my WaveIO working well (it's sounding pretty damn good even now), I'll try again. It may well be that it doesn't have much effect.

I must stress that this "back-door ground" tweak does not conform to USB specs and thus has a slight element of risk. Unless your system is "set-and-forget", it's best to stick with the Gnd line in the USB cable.

Hope that's clearer.

Last edited by Ryelands; 15th May 2012 at 01:41 PM.
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Old 15th May 2012, 02:06 PM   #740
PET-240 is offline PET-240  Australia
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Heya Ryelands,

Thankyou for taking the time to explain that! Makes a bit more sense now, I will probably play in future to experience myself, but not just yet, my Wave was posted by Lorien today so a little waiting to go for me.... :-)

Cheers,

Drew.
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