exaU2I - Multi-Channel Asynchronous USB to I2S Interface

[RayCtech]

Originally Posted by AR2

RayCTech,

just wanted to thank you for sending me to the right direction. I installed the Pure Music software and it works great. And yes I found crossover as well. It is not as powerful as Allocator, but it does the job. I will just transfer all the settings from Allocator to crossover and to parametric EQ and that will be it. And the comfort of MAC... and remote app on iPad...
I tried it before, but briefly and did not like the fact that FLAC files are converted, but I was wrong I realized after your explanation and after I installed it this weekend. They are not converted.

I see you are running Hackintosh, ha, ha. Isn't that amazing? I am still just plain amazed, when I pull my MacBookPro and run Windows XP and Sound Easy for speaker measurement... I still laugh when I do that. Macs were always from a different planet, even in System 7 days, but with OSX... and Intel chip... it is just hard to believe.

Thank you very much for the advice and your help

AR2

Hi AR2,

With Hackintosh´s I have twice (or more) the power of Mac Pro´s
And can run Windows/Linux as needed either as dualboot or virtualized.

When I now can play the huge Flac library on a Hackintosh without the need to converting - can it be any better ??

[RayCtech]

Originally Posted by SunRa

Hello all,

I have an update regarding my hiss problem with higher sampling rate material.

So here's a brief of the problem:

A. Original Beethoven 352.8K / 24 bits file from 2L HD website - hiss
B. Original Bizet's Carmen 352.8K / 32 bits floating point (forgot the source) - no hiss
C. Any other 24bits / 192k and below files - no hiss

So I did an experiment. I took the original Beethoven 352.8k / 24 bit file from 2L HD and converted it. The results are the following:

1. converted to 32 bit / 352.8k, floating point - hiss
2. converted to 32 bit / 352.8k, integer - hiss
3. down-sampled to 192k, 24 bits - no hiss

My thinking hat is not serving me very well so if you have any ideas, you are welcomed

edit: Also I mention again that I get no hiss with any 24bits / <192Khz files. Just the 352.8k / 24 bit files from 2L HD when I try to play them as they are.

There are maybe some tweaks you can try..
They may not improve anything, but here they are:

1. Check the input format MSB justified.
2. Check what happens with DFS0 and DFS1 = "1".
3. Test the slow rolloff filter function.
4. Increase the DVDD and AVDD (and voltage to the GMR´s on the exaU2I) to 5.5 volt or 6 volt...
5. Test a master clock at 45.1584MHz (41.472MHz are maximum "supported"...).

If you test point 4 and 5 you may need cooling of the chip (like I have in the pictures of the exaU2I in a previous post)..

I could not find any information of how to turn of or change the 8x interpolation filter, but this would have been the correct way to do it...

[RayCtech]

Originally Posted by NicMac

Maybe you have the only one

Hi NicMac,

As a experienced Buffalo user you may consider the exaU2I or are you waiting for the TPA USB product to be designed?

[SunRa]

Thanks RayCtech, much appreciated,

What effect should (4) have? I thought this is only in the case I want to use ak4396 with CMOS, not TTL levels. Changing the master clock (5), or the roll-off filter function (3) doesn't solve the fact that I have two 352.8k files at 32 bits playing perfectly fine, while the diethered (24 to 32bit) 352.8k are still presenting the hiss.

Regarding (1) and (2), the I2S format inputs. Isn't this only a hardware standard? I mean, can a certain PCM format generate a change in the I2S format outputed by the fpga?

Before starting to change the settings of the DAC, I would like to convert a bit these files. If you you know a free sample rate converter capable of upsampling to 352.8k, 32 bits, let me know please. The web is probably full of them but they don't have specs and I wouldn't want downloading them all. I've played with R8brain and AbyssMedia Audio Converter Plus, none of them being able to reach that sampling rate. They can convert to 32bits, with no effect though.

Also do you know where can I find the exact specs of the DXD format? Can't find them anywhere and I have the feeling this is the catch. That is, I believe that upsampled 176Khz files to 352k should play without a hiss, and the dxd files from 2L HD are encoded differently. This would explain why changing their sample rate to 192Khz allows correct playback - they are simply converted to a standard PCM file.

[SunRa]

Ok so I am back with more details.

I've converted a 176Khz file to 352.8k and it plays just fine, no hiss.

I've converted one of the 352.8k /24bits files to 176k/24 bits and then back to 352.8k and again, no hiss.

Conclusions:

There's something odd with DXD. Simple conversion of 24bits to 32 bits is of no effect. Sample rate conversion changes something in the coding of these files.

[RayCtech]

Originally Posted by SunRa

Thanks RayCtech, much appreciated,

What effect should (4) have? I thought this is only in the case I want to use ak4396 with CMOS, not TTL levels. Changing the master clock (5), or the roll-off filter function (3) doesn't solve the fact that I have two 352.8k files at 32 bits playing perfectly fine, while the diethered (24 to 32bit) 352.8k are still presenting the hiss.

Regarding (1) and (2), the I2S format inputs. Isn't this only a hardware standard? I mean, can a certain PCM format generate a change in the I2S format outputed by the fpga?

Before starting to change the settings of the DAC, I would like to convert a bit these files. If you you know a free sample rate converter capable of upsampling to 352.8k, 32 bits, let me know please. The web is probably full of them but they don't have specs and I wouldn't want downloading them all. I've played with R8brain and AbyssMedia Audio Converter Plus, none of them being able to reach that sampling rate. They can convert to 32bits, with no effect though.

Also do you know where can I find the exact specs of the DXD format? Can't find them anywhere and I have the feeling this is the catch. That is, I believe that upsampled 176Khz files to 352k should play without a hiss, and the dxd files from 2L HD are encoded differently. This would explain why changing their sample rate to 192Khz allows correct playback - they are simply converted to a standard PCM file.

The hiss could be a result of some parts of the DAC that runs with to high clocks / samplerate or simply the master clock are to low and there are not enough headroom in one of the stages or some of the stages are slightly to slow..

4. Should incease the current and thus the speed of all stages.
2. Could possibly reduce the oversampling by 0.5 if it works.

PM sent with converters info.

DXD are straight signed two´s compliment code and nothing special, only the file header have some values that identifies the file type etc..
The 2L DXD files are coded correctly as I have the DXD masters of the 23 albums 2L have recorded until now...
Something strange must happen in the player or the DAC when you play the floating point files..
I will convert one DXD file to 352.8k/32bit floating point and check what happens when played with Foobar2000, J.River, iTunes and Pure Music.

Hmmm... Your last post was interesting...
I must check this by running one DXD through the converter and check what happens..

[SunRa]

Originally Posted by RayCtech

The hiss could be a result of some parts of the DAC that runs with to high clocks / samplerate or simply the master clock are to low and there are not enough headroom in one of the stages or some of the stages are slightly to slow..

This doesn't explain why the Bizet Carmen 352.8k / 32 bits is playing without a problem, as well as another file coming from the same source also at these sampling rates and resolution.

And also doesn't explain why a 176khz file, upsampled to 352.8k also plays perfectly way.

I am at this point absolutely sure that this is not a hardware problem of the DAC. However it is not exclusive to the DXD files as you told me you dont't have any problem playing them with the ESS dac.

It's the interaction of these specific DXD files with the interface and the DAC.

[NicMac]

Originally Posted by RayCtech

Hi NicMac,

As a experienced Buffalo user you may consider the exaU2I or are you waiting for the TPA USB product to be designed?

I have considered it and my reasons for not getting it are:

1) I'm a Mac only user.
2) I have no use for 8-channel capability.
3) The price-tag is steep (say 100$ to high).
4) The lack of independent reviews.
5) Other very good (and cheaper) dedicated 32-bit USB-I2S (stereo) transports have recently become available.
6) I have only been able to get my hands on one piece of true 32-bit music...
7) Although exaU2I might be unique at this moment in time I'm convinced that in just a few months there will be very serious competitors that will push the price down and the quality up.

Just about the only TPA product that I'm not waiting for is the USB module as I believe it will be almost identical to another device I already posses.

Cheers,

Nic

[rsdio]

Originally Posted by NicMac

7) Although exaU2I might be unique at this moment in time I'm convinced that in just a few months there will be very serious competitors that will push the price down and the quality up.

The only event that will push price down is more production quantity. Making one custom electronic device is incredibly expensive. You have to make at least 100 to get the first discounts, but usually it's not enough to reach a 'fair' retail price until you make 1000. I doubt that there are even 100 people willing to build their own DAC. I could be wrong about the number of people interested, but I'm not wrong about the costs. Making 100 different products doesn't save any money - you have to have 100 people agree on the same platform and then you get discounted prices.

Quality might be pushed up by competition, especially with a forum like diyAudio to discuss what is learned by each new attempt.

[exa065]

NicMac,
You raise an interesting point. What is a good standard for an independent review?

Cheers,
exa065