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exaU2I - Multi-Channel Asynchronous USB to I2S Interface
exaU2I - Multi-Channel Asynchronous USB to I2S Interface
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Old 24th April 2011, 08:48 AM   #411
pepetono is offline pepetono  United States
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Quote:
Originally Posted by rsdio View Post
I believe that the answer is 'no.' At a minimum, you only need to share data across different DAC sections, not power.

What I am unclear about is how you would drive multiple DAC boards from the same exaU2I. The exaU2I allows an external power for the isolation component, so if you run multiple DAC boards then they will need to share digital power unless you add more isolation chips.

Keep in mind that it should be possible to separate analog and digital power supplies for a good DAC board, and thus you could have individual analog power supplies for each DAC board, but only share digital power for the I2S data. As mentioned above, you can even split the digital power supplies if you add isolation, but that might be a bit too much effort.
Thanks, yes, that is what I meant. The digital power supply of the DAC boards would need to be shared, unless extra isolation steps were taken.
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Old 24th April 2011, 08:56 AM   #412
Forane12 is offline Forane12  Bulgaria
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@RayCtech

Just yesterday a friend of mine who helps me with advice on audio electronics asked why the ExaU2I has the galvanic isolation on the output and not on the USB part and he said that he would much prefer to have what you are trying to do, please keeps us posted on your progress.
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Old 24th April 2011, 10:23 AM   #413
RayCtech is offline RayCtech
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Originally Posted by Nikola Krivorov View Post
@RayCtech

Just yesterday a friend of mine who helps me with advice on audio electronics asked why the ExaU2I has the galvanic isolation on the output and not on the USB part and he said that he would much prefer to have what you are trying to do, please keeps us posted on your progress.
This will be my last Off Topic posting in this exaU2I thread as the USB galvanic isolation and other tweaks I have posted are not specific to the exaU2I and really should have been posted in another thread or forum.

The standard exaU2I (out of the box) are by far the greatest and best performing product I to this date have used to get digital audio out of a PC and into a DAC.

As far as I am aware of (I have not found any) there is no USB galvanic isolators that supports high-speed mode (480Mbit/s), only full-speed (12Mbit/s) and low-speed (1.5Mbit/s) modes.

The progress are simply - the USB galvanic isolation works rock solid and some measurements and validation will reveal if there are any more to gain, and a decision for the maximum static voltage level the isolation should withstand.
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Old 24th April 2011, 10:36 AM   #414
rsdio is offline rsdio  United States
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Ideally, isolation should be placed between the digital section and the analog section. If you were to go to the trouble of isolating the PC USB Host from the exaU2I USB Device, then you would still need additional isolation between the USB Device digital supply and the DAC analog supply. I do not see the point of double isolation, particularly I do not see any advantage to isolating two digital sections.

Without significant testing and proof to the contrary, I would say that it is a waste of time to modify the exaU2I to isolate host and device in the digital realm. Instead, if there are improvements to be made, then they would be in providing better Analog power filtering, or perhaps even better isolation between the digital and analog sections.

Any mistakes that you make on the digital versus analog isolation will falsely cause the appearance that host versus device (USB) isolation is helping, when really it's just a Red Herring.
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Old 24th April 2011, 12:44 PM   #415
Forane12 is offline Forane12  Bulgaria
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Thanks guys, wasn't trying to steer off the thread or impose doubt on the qualities of the exaU2I, I am just seriously interested in it and the comments regarding the galvanic isolation were posted because I am not literate in that field, just my friend mentioned something about reclocking and I decided to ask. Apologies.
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Old 24th April 2011, 07:23 PM   #416
exa065 is offline exa065  Canada
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Quote:
Originally Posted by pepetono View Post
This is an interesting piece of hardware, and something I have been looking for for some time.

However, I am having some difficulty seeing how to implement what I want to do with it.
I want to have a computer based media source. Sometimes the media will be only stereo music (not interested in multi-channel music), some other times it will be the multi-channel sound track of a movie.

In any case, I need to treat the signal for those sources of material to do some room correction, and derive signals going to my main speakers, a couple of subwoofers placed in my room, and, for movie sound material, the back surround channels.

I can manage to do the DSP handling in the computer, and was hoping to output 6 channels containing the main signals + 2xSW + 2xSR ( = 6 ch)
Jose
Quote:
After reading some of the material in this thread, I though I could get away with a couple of ESS 9018 boards, one in stereo mode, the other in multichannel mode.
This is possible
Quote:

At first, I thought the Bufalo II would fit the bill for this, but it is not wired for more than stereo, and, quite frankly, I do not think I want to go for three BII boards.

Thus, I thought a compromise was in order. BII for the mains, and something like the Opus (2 of them) for the rest of my needs.
I have to investigate this. Why not? The Buffalo DACs will not use the SCK clock and the Opus DACs will use it. You will be able to play higher sampling rates on the front channels if you disconnect the Opus DACs.

Quote:
However, that would mean that the different DAC sections (of all boards) would need to share power supply, wouldn't they?
All DACs will have to share the same digital power source.
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Old 24th April 2011, 07:26 PM   #417
exa065 is offline exa065  Canada
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Quote:
Originally Posted by DUC985 View Post
got my device last week and found some time today to get it connected. Setup before was a CPlay tweaked PC with linear power suppy etc. For Audio a ESI Julia with dedicated supply connected to a Buffalo II DAC using I2S was used for quite some time.
Installing the drivers and hooking up the new device was no problem, everything worked initially like it should. There is some crackeling sound when you start the PC or shut it down. Nothing major and it does no harm to the speakers. Might be a driver initialisation issue.
The sound comming out of the Buffalo using the device compared to the Julia is simply amazing. It is not even worth comparing it. It is so much better at all frequencies. 3D image also improved by far.
I found the price initially a little bit high, but when you hear what you get it is worth every penny. I can also confirm that it works like a charm using CMP and CPlay. I have not yet tested Foobar in comparison.
This thing simply rocks !
Hi DUC985,

Thank you for sharing your experience with us . I am as excited as you are.

The noise issue that you are experiencing during PC boot and shutdown is related to the USB driver. The USB condoler hangs for a while in an undetermined state. We were unable to solve this by using FPGA logic. Future versions of exaU2I will probably have a PIC controller to add the needed processing capabilities. The unwanted sound is different on different computers. On my setup it is like whistling for about 2-3 seconds. I have it only during startup. It happens intermittently. I have an analog volume control after the DAC so it rarely bothers me.
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Old 26th April 2011, 04:43 AM   #418
exa065 is offline exa065  Canada
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Quote:
Originally Posted by MrMajestic View Post
Does anybody know the size of the exa board? Would be nice to have when planning for a case layout.
exaU2I drawing with dimensions is now published on the
www.exadevices.com > exaU2I > Specifications page.
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Old 26th April 2011, 08:01 AM   #419
luxury54 is offline luxury54  Romania
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Hello, what format does this device use for 16bit / 44.1 khz ?

is it the Philips I2S format or the Sony/EIAJ format available on it's outputs?

I mean if I would like to use it in NOS (non over sampling mode) together with a philips TDA1541A DAC which accepts only Phlilips format I2S stream would this be possible? or does it make internally some kind of OS (oversampling) already to the signal?

Thanks
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Old 26th April 2011, 08:48 AM   #420
analog_sa is offline analog_sa  Europe
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exaU2I - Multi-Channel Asynchronous USB to I2S Interface
Quote:
Originally Posted by RayCtech View Post
cut a USB cable in two and implemented galvanic isolation.....

What, not even a hint of how this was achieved??? The isolation, not the cutting.

Only joking. A good working USB isolator is a very marketable product. Congratulations.
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