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Old 26th April 2011, 09:02 PM   #431
rsdio is offline rsdio  United States
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Originally Posted by analog_sa View Post
And this is a serious problem as far as your understanding of high-end digital audio goes. Textbook solutions which work just fine in other types of electronics are not necessarily suitable for serious audio.
There is nothing lacking in my understanding of high-end audio. If you care to give an example where digital isolation improves a situation without analog isolation, or even where digital isolation improves a situation with analog isolation, then I would be very interested. In the former case, I would say that the mistake is to not have analog isolation in the first place, such that the digital isolation is inferior to analog isolation. In the latter case, I would say that the analog isolation is insufficient if digital isolation can improve upon it.

But before we go any further, I would like to ask whether you have any electronics design experience at all, or if you are just reciting articles from popular audiophile literature.
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Old 27th April 2011, 11:50 AM   #432
exa065 is offline exa065  Canada
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Originally Posted by luxury54 View Post
thank you both for your answers...perhaps i wasn't that specific about my question;
as you all know there are 2 standards of the I2S stream that reaches a specific DAC depending of the various decoders used in cd players;
We use the Philips I2S standard.
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Old 27th April 2011, 01:01 PM   #433
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Originally Posted by rsdio View Post
But before we go any further, I would like to ask whether you have any electronics design experience at all, or if you are just reciting articles from popular audiophile literature.
Priceless
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Old 2nd May 2011, 04:02 AM   #434
kazap is offline kazap  England
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I wonder if I can get some opinions about a nutty idea I just had.

Is there any merit in feeding my stereo DAC that has eight DA chips with eight I2S streams via the exaU2I?

I have the Audio-gd REF7 šÍ§Ó*ĩ响. I really like the sound signature of this eight piece PCM1704 R2R mono chip but it does seem to be very sensitive to jitter.

The REF7 is fed by SPDIF and has a jitter reducing DSP module (http://www.audio-gd.com/Pro/dac/DSP1/DSP1ENspecs.htm Two-channel Digital Interpolation Filter and data in-phase processor for digital audio),that takes I2S, upsamples if you like and splits I2S into left and right channels for the mono PCM1704's (four on each side).

I guess Foobar can use VST (Virtual Studio Technology) and DSP's to create four left only channels and four right only channels.

If these were taken out of the exaU2I by identical wires to feed each chip discreetly would it work?

If it makes music I wonder if you might care to speculate which will sound better.
A)a single I2S stereo signal to the DSP-1
B) Eight discreet I2S mono signals - one per PCM1704

Cheers

Last edited by kazap; 2nd May 2011 at 04:21 AM.
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Old 2nd May 2011, 04:47 AM   #435
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[QUOTE=rsdio;2552265]There is nothing lacking in my understanding of high-end audio. If you care to give an example where digital isolation improves a situation without analog isolation, or even where digital isolation improves a situation with analog isolation, then I would be very interested. In the former case, I would say that the mistake is to not have analog isolation in the first place, such that the digital isolation is inferior to analog isolation. In the latter case, I would say that the analog isolation is insufficient if digital isolation can improve upon it.


I am not sure if I understand you completely, but I recall the designer of the HRT Music streamer stating that he thought ground isolation of the incoming digital stream was of the utmost importance, it is rather easier to clean and isolate the power supply grounds from the computer. Mind you his device was USB bus powered so maybe he had a vested interest in saying that.
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Old 2nd May 2011, 08:04 AM   #436
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Quote:
Originally Posted by kazap View Post
I wonder if I can get some opinions about a nutty idea I just had.

Is there any merit in feeding my stereo DAC that has eight DA chips with eight I2S streams via the exaU2I?

I have the Audio-gd REF7 šÍ§Ó*ĩ响. I really like the sound signature of this eight piece PCM1704 R2R mono chip but it does seem to be very sensitive to jitter.

The REF7 is fed by SPDIF and has a jitter reducing DSP module (http://www.audio-gd.com/Pro/dac/DSP1/DSP1ENspecs.htm Two-channel Digital Interpolation Filter and data in-phase processor for digital audio),that takes I2S, upsamples if you like and splits I2S into left and right channels for the mono PCM1704's (four on each side).

I guess Foobar can use VST (Virtual Studio Technology) and DSP's to create four left only channels and four right only channels.

If these were taken out of the exaU2I by identical wires to feed each chip discreetly would it work?

If it makes music I wonder if you might care to speculate which will sound better.
A)a single I2S stereo signal to the DSP-1
B) Eight discreet I2S mono signals - one per PCM1704

Cheers
Maybe exa065 should have answered this - but I take my chances and I hope exa065 corrects me if I am inaccurate or wrong...

Your question started me thinking and as I have experimented a bit with the exaU2I I believe both PCM1704 and other DACīs could work as mono DACīs with a correct configuration of the exaU2I ASIO driver

The PCM1704 could be driven directly by the exaU2I as you can set up the ASIO driver to output Left channel for both channels of I2S channel 1, then Right channel for both channels of I2S channel 2.
In this case you could have full 384k sample speed support as it uses the 4 channel mode of the exaU2I.

If you map I2S channel 3 and 4 like channel 1 and 2 you would double the number of outputs and could drive additional DAC chips directly, but now the 8 channel mode of the exaU2I are used and the maximum sample rate are lowered to 192k.

In the case of the PCM1704 it should handle samplerates up to 768k, but I do not know if this 768k in as in mono or stereo.
When using the exaU2I in 4 channel mode with support for 384k the PCM1704 will be feed with up to either the full speed or the half speed of the supported sample rate speed.
This will also act as a "kind" of upsampling as the PCM1704 now will receive the double rate of the data as two Left or Right samples (identical) will be sent to the DAC, but without any damaging upsampler with dither or any digital filters with damaging pre and post ringings etc..

44.1k -> "upsampled" to 88.2k
48k -> "upsampled" to 96k
88.2k -> "upsampled" to 176.2k
96k -> "upsampled" to 192k
176.4k -> "upsampled" to 352.8k
192k -> "upsampled" to 384k
352.8k -> "upsampled" to 705.6k
384k -> "upsampled" to 768k

The PCM1704 have a pin to select inversion of the data so balanced outputs are easily implemented.

In the case of all other current output DACīs this ASIO setup configuration could also be used and effectively create mono DACīs out of a stereo / 2 channel DAC with the "upsampler" effect without the damaging pre and/or post ringing digital filter...
It is just to sum the current outputs of the two channels of the stereo / 2 channel DACīs before the I/V stage...
This will in addition give a ca. 3dB improvement in noise / THD as a bonus..

Also voltage output DACīs can use this setup, but the left and right channel on each DAC must then be summed to get the benefits.
The implementation of the outputs of the actual DACīs may require different approaches to make it work...

As @kazap very good question gave me the "solution" to implement the PCM1704 (and other DAC chips) without any upsamplers, DSPīs or digital filters and with a effective 2x upsampling without the damaging effects of upsamplers, DSPīs or digital filters and then use my remotely controlled variable gain JFET I/V stage as volume control I have a near perfect setup I apparently must make as a prototype for evaluation..

Last edited by RayCtech; 2nd May 2011 at 08:27 AM.
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Old 2nd May 2011, 09:08 AM   #437
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Originally Posted by RayCtech View Post
In the case of all other current output DACīs this ASIO setup configuration could also be used and effectively create mono DACīs out of a stereo / 2 channel DAC with the "upsampler" effect without the damaging pre and/or post ringing digital filter...
It is just to sum the current outputs of the two channels of the stereo / 2 channel DACīs before the I/V stage...
This will in addition give a ca. 3dB improvement in noise / THD as a bonus..
I have for some time had the upcoming Arda AT1401 DAC in mind for a possible solution...
But the AT1401 will not be able to be used with the above mentioned benefits as it extracts only half the samples out of the data stream.
This feature makes it easier to implement as it does not require a DSP or digital filter with dedicated left and right channel outputs, but as said it eliminates the possible benefits....
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Old 2nd May 2011, 09:54 AM   #438
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The optimal setup with the exaU2I and the PCM1704 may be as follows:

1. Galvanic isolation of the USB, and a local 5 volt power supply for the exaU2I.
2. Connect the PCM1704 chip inputs directly to the exaU2I by bypassing the GMR I2S galvanic isolation and with its own + and - 5 volt power supply.
3. Use the automatic LSB extension setting of the ASIO driver and the PCM1704 will get "correct" 24 bit data (with 16 bit sources) and the Bipolar offset servo of the PCM1704 will deal with the LSB offsets below 23 bit...
This is mostly important when using the PCM1704 in the inverting mode (balanced setup) as 16 bit data then will create a 1/2 LSB error (at 16 bit level) that the PCM1704 cannot correct due to the Bipolar offset servo works below 23 bit resolution.

With this setup the only clocks in use are the low jitter clocks of the exaU2I..
My math (calculator) indicates a possible theoretical improvement of the jitter in
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Last edited by RayCtech; 2nd May 2011 at 10:09 AM.
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Old 2nd May 2011, 11:46 AM   #439
kazap is offline kazap  England
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Quote:
Originally Posted by RayCtech View Post
The optimal setup with the exaU2I and the PCM1704 may be as follows:

1. Galvanic isolation of the USB, and a local 5 volt power supply for the exaU2I.
2. Connect the PCM1704 chip inputs directly to the exaU2I by bypassing the GMR I2S galvanic isolation and with its own + and - 5 volt power supply.
3. Use the automatic LSB extension setting of the ASIO driver and the PCM1704 will get "correct" 24 bit data (with 16 bit sources) and the Bipolar offset servo of the PCM1704 will deal with the LSB offsets below 23 bit...
This is mostly important when using the PCM1704 in the inverting mode (balanced setup) as 16 bit data then will create a 1/2 LSB error (at 16 bit level) that the PCM1704 cannot correct due to the Bipolar offset servo works below 23 bit resolution.

With this setup the only clocks in use are the low jitter clocks of the exaU2I..
My math (calculator) indicates a possible theoretical improvement of the jitter in
Thanks for the intriguing design ideas.
Its even more complicated then I had imagined.
I wonder what your math indicated, in terms of a jitter figure, with your design?
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Old 2nd May 2011, 12:10 PM   #440
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Originally Posted by kazap View Post
Thanks for the intriguing design ideas.
Its even more complicated then I had imagined.
I wonder what your math indicated, in terms of a jitter figure, with your design?
It appeare that a whole section was removed by accident when I edited the post...

A calculated improvement in jitter of up to 60 dB...
It may not be measurable by more than a few dBīs..
But I expect it would affect the fidelity...
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