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Old 15th May 2012, 07:14 PM   #751
rsdio is offline rsdio  United States
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Quote:
Originally Posted by Ryelands View Post
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.
I'm not sure that you make a clear distinction. Audio transfers are not precisely real time, because the DAC is in total control of the timing. They're really near-real-time.

On the one hand, disk drives use Bulk mode, which will retransmit any piece of data that is not acknowledged due to transmission errors. Audio devices use Isochronous mode, which can detect transmission errors, but there is no time to retransmit. You are correct to point out that there is a difference between a disk drive and an audio device, but in practical terms there really are no transmission errors on modern USB hardware. When you take into consideration the fact that both are basically 100% reliable, there's not much difference. In other words, your statement "So long as the thing works, it works fine" can be applied equally to disk and audio devices.

Some DIY audio interfaces even go so far as to use Bulk mode, which almost proves that it's valid to compare USB disk drives and USB audio devices. I do not condone the use of Bulk mode for audio, because it does not allow the OS to properly allocate available bandwidth to "real time" needs or schedule packets correctly, but there does seem to be very little difference between devices.
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Old 15th May 2012, 07:20 PM   #752
rsdio is offline rsdio  United States
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Quote:
Originally Posted by Ryelands View Post
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.
I agree with these statements in general, but I want to point out that there are USB Audio devices other than WaveIO which operate with asynch timing. As a class, the (near real time) asynch USB Audio devices are going to have a much better chance of producing good audio quality compared to real time USB Audio devices that use one of the other optional timing mechanisms (i.e. not asynch).
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Old 15th May 2012, 08:51 PM   #753
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Quote:
Originally Posted by Lorien View Post
. . . I thought it would be a good idea to cut USB +5v, USB GND and USB Shield wires from one of my USB cable and try to see if WaveIO will work this way.
To clarify, I do NOT, repeat NOT (as in "don't", as in "refrain from", as in, well, take your choice . . .), advocate trying, let alone using, a USB connection without a ground connection between the computer (aka the host) and the device or without a 5-volt signal at the B-connector end.

What I am saying is that:

1. provided there is a robust ground connection elsewhere (definitely not one relying on haphazard links through safety earth) between the host and the device, then - but only then - the USB cable does not absolutely have to have a ground line for the device to work. The envisaged scenario would most likely be realised by hard-wiring the Gnd of the PC's PSU to the Gnd of the device's PSU. The Gnd is (emphatically) NOT omitted, it is re-routed;

2. the 5-volt feed to the appropriate pin on the B-connector at the device end of the cable can be obtained from a separate PSU rather than from the host's USB port. This is a commonplace tweak that is commercially available and (hopefully) uncontroversial;

3. the screen that is quite properly part of the USB cable spec can be omitted in some situations (subject to test) where an effort has been made (as you'd expect in any half-decent PC audio setup) to minimise RF emissions from the host;

4. when I have tried such reconfiguration, I have observed a worthwhile improvement in sound quality when using a conventional (i.e. adaptive) USB connection to a DAC. As I stressed, I have not tried it with an asynch device such as the WaveIO and so have no idea if it would offer any improvement in SQ. It might - but it might well not.

Apologies if I didn't make this clear.
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Old 15th May 2012, 10:04 PM   #754
PET-240 is offline PET-240  Australia
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G'day Ryelands, 1audio and others who've added to this grounding discussion,

Thankyou muchly for taking the time to explain these things, have learnt much about USB which I had no idea about, just goes to show there's more to baking bread than flour and water!

Much appreciated!

Drew.
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Old 15th May 2012, 10:24 PM   #755
reo is offline reo  Canada
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Quote:
Originally Posted by suffolk tony View Post
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!
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?
No need to disable the on-board clocks on the buffaloII., that procedure is only necessary if one wants to use the master clocks of the WaveI/O card.

Last edited by reo; 15th May 2012 at 10:39 PM.
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Old 16th May 2012, 01:14 AM   #756
abanico is offline abanico  Spain
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Default Thanks Lorien

I purchase this board to upgrade a Bryston BDA-1 DAC .The dac is input transformer coupled (similar or identical to scientific conversion ones)so Lorien left the output transformer unmounted. I' ve been lucky as the board is sounding outstanding. I've made in two separate boxes.one for the power supply (.AMB labs sigma 11) feeding the board threw an umbilical cord and going to the dac at a Bnc input. My latop has a linear power supply .( the red spikes of thesycon test ,disappear with the power supply)
The first thing to notice is the silence .Ripped songs sound very very close and the noise floor is similar as played with two goods transports (meridian ,linn ).One month of listening ,unplugging the bnc to cut completely the influence of pc and i think it's not necessary to cut the ground of the usb.
I' ve made an improvement making a usb cable .3 conductors + shield a genuine balanced cable designed to leave the shield floating at receiver end.
It's sounding much better than a wireworld starlight of the same length.
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Old 16th May 2012, 01:22 AM   #757
abanico is offline abanico  Spain
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Sorry i forget the link for the cable.
http://www.ebay.es/itm/Nerve-Audio-V...item5ad2acfac4
24/192 Music Downloads are Very Silly Indeed
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Old 16th May 2012, 12:14 PM   #758
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Default gnd loop problem

Maybe someone can give me a help with a ground loop problem I encountered with WaveIO isolated I2S.
I attached a couple of schemes to understand the situation better.
Power supply grounds are not normally shared at ps level.

With non-isolated I2S everything is fine, free of hum.

With isolated I2S I get a quite annoying at medium-high volume hum noise from both channels.

I get rid of hum if:
- detach usb cable
- detach notebook AC plug (power from battery)
- share PS1 gnd with each other PS ground

PS2, PS3 and PS4 grounds are tied at dac level, so if I share PS1 gnd (that should be shared with usb gnd) with other PS grounds I lose the gnd isolation between usb and I2S.

What do you think?
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Old 16th May 2012, 02:46 PM   #759
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What do you measure for voltage between the "isolated" ground and DAC ground?
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Old 16th May 2012, 05:28 PM   #760
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Quote:
Originally Posted by reo View Post
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?
No need to disable the on-board clocks on the buffaloII., that procedure is only necessary if one wants to use the master clocks of the WaveI/O card.
Many thanks for your helpful reply Reo.
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