No, I'm just ignoring it
My next dac project will take this problem into account though. As for now I'll just live with a non bit perfect dac.
So what you're saying is that if the timing requirements for LE and BCK is correct, you still couldn't feed the dac with a 16-bit signal in a 32-bit data stream? I had the impression that the dac only latched in the last 18-bits of the data stream after LE goes low.
Problem here is that LE goes low one cycle too early.
Ok, I get it now. The audio bits lie in the beginning of the I2S data stream, and the AD1865 only latches the last 18 bits. So with a 16 bit audio signal, only the two least significant bits would be latched.
What I find really interesting is that when I attenuate the signal digitally by 78 dB in the software I get a normal output signal. Definitely more than ten bits. 78 dB attenuation equals dividing the signal by ~2^13, or the same as shifting the data 13 bits to the right.
It's a surprising result to me. But it works!
So long as the software is working with the full 24bits and the exa handles the full 24bits then this is correct. Why not use digital attenuation to set the correct bit position for your DAC? As you say, it works! But with a 13 bit shift of a 24 bit signal your DAC must be only receiving 11 bits. Or is the software actually working at 32bits? In which case there's no problem at all, your DAC will be getting sent 19 bits (but natually ignoring one of them).
The software actually works at 64 bits, but the datastream sent to the exa is 32 bits. The correct amount of shifting would be 14 bits minus 1 bit, since the LRCK in the I2s stream goes low one cycle too early for the dac. So 13 bits should be just about right. That equals 78.26779887... dB
Painkiller,
Now you are absolutely right.
You can use 2pcs of 8bit flip flop with pararell output - so you can easy set right delay by choosing coresponding output pin Qx. This solution works very good.
And ofcourse additionally you have to negate LRCLK to provide latch signal to second channel.
Now you are absolutely right.
You can use 2pcs of 8bit flip flop with pararell output - so you can easy set right delay by choosing coresponding output pin Qx. This solution works very good.
And ofcourse additionally you have to negate LRCLK to provide latch signal to second channel.
I'm still worried about the propagation delay of these IC's, when running 192 kHz. With only two of these shift registers, you're around 24 ns delay, and close to getting timing errors. That means you should consider delaying all the other digital lines with nand gates also. Or else you need additional reclocking. It's not supposed to be easy. Bit shifting by accurate volume leveling in the software is the easiest solution yet.
Is there any degradation to be expected with the exaU2I if other USB-ports are busy as well?
Specifically, I would like to connect a USB-HD, which contains all my music files to one USB-port and the exaU2I to another USB-port. A mouse and keyboard will be connected to futher USB-ports.
I´m a bit worried about the USB-HD, since the PC will now have to do all the file reading (wav-files) via USB and serve the exaU2I at the same time. I plan to use a low power, passively cooled PC for this, so there is limited computer power available. I´m thinking about an AMD Fusion E350, for which Asus has a very nice passively cooled mini itx mainboard.
Any experience from exaU2I users who play their music from an attached USB-HD rather than from an internal SATA-HD?
Specifically, I would like to connect a USB-HD, which contains all my music files to one USB-port and the exaU2I to another USB-port. A mouse and keyboard will be connected to futher USB-ports.
I´m a bit worried about the USB-HD, since the PC will now have to do all the file reading (wav-files) via USB and serve the exaU2I at the same time. I plan to use a low power, passively cooled PC for this, so there is limited computer power available. I´m thinking about an AMD Fusion E350, for which Asus has a very nice passively cooled mini itx mainboard.
Any experience from exaU2I users who play their music from an attached USB-HD rather than from an internal SATA-HD?
Why not buy an external SATA-HD enclosure ?
With most kits you get an internal SATA to external SATA cable.
I would also recommend a Zotac ITX motherboard with a Intel i3 2105 or a i5 2405S CPU and a SSD system HD.
You also get a working eSATA connector on the motherboard
The Asus ITX board also has an eSATA connector. However, the passively cooled Zotac is certainly an alternative I'm going to check out. Thanks for mentioning it.
I was more thinking about a USB-HD than an eSATA-HD because of the wide available choice, also of very quiet models.
Best solution in this case is to have music files on an SATA HD (eSATA). Best of all is to use an SSD on eSATA. Then you can use from USB port only +5v to power the eSATA (SSD) HD. An CLC filter on that 5v power line from USB port is also recommended...
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There are a lot of folks "into" the AD1862, AD1865, PCM56, PCM58, even PCM1702/1704. Good dac's really. But the I2S connection sans digital filter is always problematic. Wouldn't it be nice if the exa firmare or maybe even the driver software could be configurable for the DAC of choice. I mean this thing has 8 channels right? Why not for stereo split the I2S into L&R combatible format for these different DAC's. Just click the mouse to pick AD1865. It would be a huge advancement for all the NOS builders. Even if you aren't into NOS you could use the computer to upsample, which would allow a better analog filter. The potentital is there really, and with Hirez becoming more popular a 24/192 PCM1704 NOS DAC starts to make a lot of sense to even those not into NOS. Heck there are even reports of some new commercial NOS PCM1704 beating the PM2.
Just saying there is a potentital to really expand this. In a few years you can bet a lot of folks will be oversampling with their computer (custom PC digital filtering), this would be a step in that direction.
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What would be the advantage of using a second cable to supply power from usb to an external eSATA-HD? The eSATA cable already supplies the required power. If supply filtering improves SQ, this could be done in the eSATA cable or (much better) in the external eSATA case.
Yes, an SSD for the music files would be nice. But I´m needing about 2 GB, which costs peanuts as a HD, but is still unrealistic as an SSD.
Back to the original question: Is there any experience of using the exaU2I when the music files are on an external USB-HD instead of an internal SATA-HD? Sound quality? Degradation with HD-files?
I have to recognize that my earlier post was quite confusing. I had to be more specific...
I personally use an ordinary SSD as external HD, and I have a SATA cable which is normal on one end and eSATA connector in anther end. I use an eSATA port to connect this standard SSD to. So, is not any power for the HD in this set up. That because I have to use an USB port to power my SSD HD.
Referring to your question, there is no any advantage to use another power supply if one use exclusively eSATA interface on eSATA device. But I would want to have that filter anyway on power rail.
On the player I have there is an difference between using USB as HD interface and using an existing eSATA port for HD with the music files. In my case it sound better with HD on the SATA. Else, if is about a PC-media machine with exaU2I on USB I think is better to have the files on internal SATA. If one use an external/mobile HD to a dedicated media PC or player, then is an advantage to have one external HD, which can be connected where is need it for playing/update the files.
The only problem I can see is when data transfer ocure on USB interface (using USB HD), and in the same time, the same type interface in a PC is used for drive exaU2I. I would prefer to have a different interface involved in reading files/data than I will use for output with exaU2I.
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Sorry, you are of course right. The eSATA cable has balance transmission for send and receive, but power to the external drive is provided from a small power supply from the mains. You could possibly put additional filtering there or replace it with a linear supply to test if this affects SQ.
There are some external HDs with both USB and eSATA connectors, a little more expensive, but still reasonable. So this will most likely be my way to go. My internal drive will be a silent SSD, which need not be very big since the music files are on the external drive.