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Old 2nd April 2011, 12:09 PM   #241
rsdio is offline rsdio  United States
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Quote:
Originally Posted by soundcheck View Post
You can IMO achieve highest qualities with SPDIF if properly implemented.
Your statement is somewhat unclear.

Are you saying that the highest quality can only be achieved with SPDIF?
Or, are you saying that SPDIF can only approach the highest quality if properly implemented?

The former would be incredibly difficult to prove.

IMO, SPDIF presents the single largest challenge when aspiring for the highest quality. Similarly, by avoiding SPDIF, the highest quality is much easier to achieve. The same goes for similar technologies such as TOSLINK and AES3.
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Old 4th April 2011, 06:21 AM   #242
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Hi. I wonder if this module can work with this PCM > PWM amplifier?

miniAMP | miniDSP

This amplifier takes i2s and uses TAS5704 for amplificaiton.

This way, we can even bypass the DA conversion
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Old 4th April 2011, 07:29 AM   #243
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Quote:
Originally Posted by rsdio View Post
Your statement is somewhat unclear.

Are you saying that the highest quality can only be achieved with SPDIF?
Or, are you saying that SPDIF can only approach the highest quality if properly implemented?

The former would be incredibly difficult to prove.

IMO, SPDIF presents the single largest challenge when aspiring for the highest quality. Similarly, by avoiding SPDIF, the highest quality is much easier to achieve. The same goes for similar technologies such as TOSLINK and AES3.
What I'm saying is that SPDIF or whatever interface, assuming bitperfect
delivery of bits, should become irrelevant if the receiving end would do a good job.

There are just a very few devices out there e.g. Apogee Big Ben, which seem to be able to handle that challenge quite good.

I tweaked my SB Touch SPDIF output & my receiver input & PS and I'm pretty happy happy with the result. My former USB+I2S reclocker interface wouldn't beat that.

SPDIF is known not to be the best interface. Still I consider it the most flexible.

Honestly - I don't want to end up with proprietary ASIO Windows only USB drivers anymore. If USB then standard USB drivers ( these support asynchronous USB) on
all platforms should do. I don't want to be tied to a certain OS because of the soundcard driver. This is absolutely unacceptable to me.
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Old 4th April 2011, 09:17 AM   #244
rsdio is offline rsdio  United States
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Quote:
Originally Posted by soundcheck View Post
What I'm saying is that SPDIF or whatever interface, assuming bitperfect delivery of bits, should become irrelevant if the receiving end would do a good job.
What you describe is only true if you ignore time. When I transfer a DAT recording to my computer, SPDIF is perfectly fine, and there isn't even any advantage to switching to AES3 in that case. I'm merely copying bits to a file. However, playback of audio in real time requires synchronization of the source media and the playback DAC clock. Just because SPDIF allows this to happen without incident 99.9% of the time does not mean that it works 100% of the time. In other words, you always run the risk of repeating or losing a sample unless you delay the playback by a substantial number of samples. i.e., You can design your DAC to follow the SPDIF clock and suffer from jitter, or you can reclock the data and suffer in other ways.

Quote:
There are just a very few devices out there e.g. Apogee Big Ben, which seem to be able to handle that challenge quite good.
Throwing around a renowned name like Big Ben has absolutely nothing to do with what we are discussing here. Apogee's Big Ben is a master clock source. It does not convert audio bits into analog signals, i.e., Big Ben is not a DAC. Big Ben cannot handle the challenge of synchronizing the media source to the DAC unless you have a transport with an external clock input, and those are quite rare unless you want to hack your own. The problem is that such a solution, although possible, is overly expensive and involves three devices (master clock, media transport with external clocking, DAC with external clocking) when you really only need two (media transport and DAC with bidirectional communication).

I prefer the simpler, less expensive solution. It's always easier to engineer the better solution when the design itself is as simple as possible, and so long as the design does not unnecessarily introduce problems that need additional engineering to solve.

Quote:
I tweaked my SB Touch SPDIF output & my receiver input & PS and I'm pretty happy happy with the result. My former USB+I2S reclocker interface wouldn't beat that.
If you are happy, then perhaps the jitter noise is inaudible in your situation. Jitter noise is not always inaudible, but the good news is that it can be avoided simply by avoiding SPDIF and similar unidirectional communications.
I have no idea what kind of USB+I2S reclocker you were using, but perhaps it was based on unidirectional clocking from the media transport, in which case it would have suffered the same issues as SPDIF. Take note that reclocking is entirely unnecessary when the media transport slaves to the DAC clock.

Quote:
SPDIF is known not to be the best interface. Still I consider it the most flexible.
I will agree that SPDIF is widespread, convenient, and at least some part of your system should probably have an SPDIF input for compatibility with outdated gear. However, given the options today, my primary listening path will not involve SPDIF or TOSLINK or AES3. As more people demand an end to easily avoided jitter, SPDIF will perhaps become less of a need.

Quote:
Honestly - I don't want to end up with proprietary ASIO Windows only USB drivers anymore. If USB then standard USB drivers ( these support asynchronous USB) on all platforms should do. I don't want to be tied to a certain OS because of the soundcard driver. This is absolutely unacceptable to me.
On this point I entirely agree. While I have due respect for exaU2I and the USB-to-I2S project, it's not for me, either.

Simply put, the choice of the FTDI USB chip makes an official implementation of a USB-Audio driver impossible, and thus I consider the design flawed for my use. As a hardware designer and firmware developer, I would have recommended choosing the Cypress SX2 or FX2LP chips. The Cypress chips are fully programmable, and could implement the USB-Audio specification. There are also other programmable options. The FTDI Chip cannot implement the USB-Audio specification, and therefore it is doomed to custom drivers on Windows, Linux, and OSX.

Many hardware designers cite the lack of USB-Audio support on Windows as the reason for choosing a non-standard implementation, and claim that the support in OSX does not represent a big enough market. But it just doesn't make sense, IMO, to go to the trouble of developing proprietary ASIO drivers when a proprietary USB-Audio driver would make the overall hardware design compatible with more systems.
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Old 4th April 2011, 11:17 AM   #245
Raj1 is offline Raj1  United Kingdom
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Quote:
Originally Posted by soundcheck View Post

I tweaked my SB Touch SPDIF output & my receiver input & PS and I'm pretty happy happy with the result. My former USB+I2S reclocker interface wouldn't beat that.

What jitter levels did you achieve with these mods?
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Old 4th April 2011, 01:23 PM   #246
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1. Time

In the pro-audio world latency matters. It's irrelevant for
home audio.
And most of the devices (incl. EXA) buffer and delay anyhow.
You'll also find buffers in e.g. NAIM DACs, PS Audio stuff asf.
Not to forget all these streaming clients which buffer 20-30s or
more.

The majority of interface providers fail on decoupling input
originated distortions (noise/jitter).
Even the majority of super expensive asynch USB DACs won't make it.

2. Apogee BB

It's also a reclocker. And it works quite good on SPDIF. I havn't said
that I'd buy it. I listened to it and it left a nice impression on me.
The Appogee was feeding an Antelope Zodiac Gold btw. Not the suposedly worst commercial DAC out there.


3. SPDIF or USB

Doesn't matter what I tried. I could not find any device which decouples
propery from the PC side. Let me know if there's an interface out there.

I used to use an USB-reclocker from EC-Designs btw.

It's a myth that asynchronous USB is the holy grail of slaving/decoupling a transport.

Slightest variations on the PC will have an impact on the output. You can find tons of info and experiences about it on AA and elsewhere.

4. Jitter levels achieved

No idea. I'm not a manufacturer. I can't afford that kind of lab gear.

I was desperately looking for somebody who'd be willing to take some measurements on my SB Touch Toolbox optimizations.
I even talked to some "professionals" about it. I can tell you. I still havn't found anybody supporting a "community effort".



Cheers
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Old 4th April 2011, 02:19 PM   #247
Bunpei is offline Bunpei  Japan
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Quote:
Originally Posted by ackcheng View Post
Hi. I wonder if this module can work with this PCM > PWM amplifier?
It's very interesting! It reminds me of Koon's TAS5706 Class-D amplifier.
http://koonlab.com/TAS5706/TAS5706.html

For me, the amplifier seems to accept I2S output signals from exaU2I
without problems. I can't guarantee it, however.

When we handles I2S interface, we should consider;
1. Signal Level
+3.3 V, +5 V or LVDS differential?
In this case, +3.3 V. OK.
2. BCLK
32*fs, 64*fs or fs dependent?
In this case, 64*fs?
3. MCLK
256*fs, 512*fs or fs dependent?
Autodetect or register setting mandatory?

As for 2. and 3., the amplifier seems to autodetect clock frequencies.
There will be no problems.

One concern is there is no volume function in exaU2I nor miniAMP.
You need to use digital volume function in your player program on PC.
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Old 4th April 2011, 02:42 PM   #248
exa065 is offline exa065  Canada
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Quote:
Originally Posted by Bunpei View Post
It's very interesting! It reminds me of Koon's TAS5706 Class-D amplifier.
http://koonlab.com/TAS5706/TAS5706.html

For me, the amplifier seems to accept I2S output signals from exaU2I
without problems. I can't guarantee it, however.

When we handles I2S interface, we should consider;
1. Signal Level
+3.3 V, +5 V or LVDS differential?
In this case, +3.3 V. OK.
2. BCLK
32*fs, 64*fs or fs dependent?
In this case, 64*fs?
3. MCLK
256*fs, 512*fs or fs dependent?
Autodetect or register setting mandatory?

As for 2. and 3., the amplifier seems to autodetect clock frequencies.
There will be no problems.

One concern is there is no volume function in exaU2I nor miniAMP.
You need to use digital volume function in your player program on PC.
Bunpei,

May I kindly ask you to allow me to handle the support questions for exaU2I myself?
As a vendor offering a competing device obviously you have a conflict of interest when you post here. I've been restraining myself from using the SD card player discussion thread as a platform for publicity for exaU2I. These forums are created for the benefit of the genuine DIY users and we as vendors have the responsibility to respect each-other's boundaries.
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Old 4th April 2011, 02:52 PM   #249
exa065 is offline exa065  Canada
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Join Date: Feb 2011
Quote:
Originally Posted by ackcheng View Post
Hi. I wonder if this module can work with this PCM > PWM amplifier?

miniAMP | miniDSP

This amplifier takes i2s and uses TAS5704 for amplificaiton.

This way, we can even bypass the DA conversion
There should be no problem to use any device that has a standard I2S input. Please check the Terminal Functions section on the DIY Guide on our website: www.exadevices.com > exaU2I > D.I.Y. Guide.

Best regards,

exa065
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Old 4th April 2011, 03:02 PM   #250
exa065 is offline exa065  Canada
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Quote:
Originally Posted by soundcheck View Post
1. Time

In the pro-audio world latency matters. It's irrelevant for
home audio.
soundcheck, you are missing the point about "time" in rsdio's answer. It is not about Latency. It is about Jitter.
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