I am making a low power linux system to play my music, and i am looking for a DAC (to supply into a t-amp). I would like it to be of a similar quailty (or better, of course!) to the modded PS1 cd player, whilst remaining as affordable as possible. I don't have an aversion to modding/hacking anything, etc. I want this to live in the same (small) box as the PC, so i'm not looking at a prebuilt commerical DAC unit.
What are the best options?? If there is no cheap option, i'd like to hear the cheaper alternatives, too, and how they compare?
What are the best options?? If there is no cheap option, i'd like to hear the cheaper alternatives, too, and how they compare?
I would guess USB input. (I'm not fussy but i don't intend to have a coax or spdif output, nor do i see the point; i thought USB was better).
I'm not sure what your power supply question is asking.. i don't mind an external power supply, obviously that would be relevant to the cost.
I don't know what $X gets you, which is why i didn't put a price. As low as possible. But i've given you an idea of what sort of league i'm aiming at, the PS1. But i don't know how easy this is, either. I'm in the UK. (but even if you recommend me something i can't get, it would give me a good starting point).
I'm not sure what your power supply question is asking.. i don't mind an external power supply, obviously that would be relevant to the cost.
I don't know what $X gets you, which is why i didn't put a price. As low as possible. But i've given you an idea of what sort of league i'm aiming at, the PS1. But i don't know how easy this is, either. I'm in the UK. (but even if you recommend me something i can't get, it would give me a good starting point).
I haven't had a chance to read all the links provided but since the replies are coming fast, i'll put in a quick response. The HRT streamer II ($150) is more than i was considering, for this application. Also, i'm looking an an 'embedded' pc board, so likely no PCI for a soundcard (but a sound card is more than just a DAC so shouldn't a similar DAC be cheaper anyway?.. and it forces power from the PC which would be a bad thing right?).
Many truly embedded boards (with e.g. ARM SoC - beagleboard), feature I2S outputs from the SoC, ready to hook to a DAC chip ( Need a starting point for DAC/preamp setup with BeagleBoard for audio processing - General Questions - Twisted Pear Audio Support ). But you are probably looking at x86 hardware. E.g. Alix 1D has one PCI slot.
Generally, ARM boards are cheaper than x86 ones 
Of course the long awaited Raspberry Pi would be an interesting contender RaspberryPiBoard - eLinux.org
But a less powerful board should do too.
BUT. Just as most of the USB DACs, your I2S clock will be PLL-generated on all these boards. They do not have dedicated crystals for audio. In fact, only very few USB asynchronous DACs above your stated price level do.
That is the beauty of the PCI cards I am talking about E.g. Mikrotik RB230 has one regular PCI slot http://www.luxus.cz/obchod_pic/rb230.jpg
Of course the long awaited Raspberry Pi would be an interesting contender RaspberryPiBoard - eLinux.org
But a less powerful board should do too.
BUT. Just as most of the USB DACs, your I2S clock will be PLL-generated on all these boards. They do not have dedicated crystals for audio. In fact, only very few USB asynchronous DACs above your stated price level do.
That is the beauty of the PCI cards I am talking about
E.g. Mikrotik RB230 has one regular PCI slot http://www.luxus.cz/obchod_pic/rb230.jpgnothing in alt processor SBC land will be cheaper than windows PC compatible soundcards - the economies of 10k-1M quantity mass produciton can't be had with nonstandard interfaces, a USB Audio Class DAC is probably the next best option
do the cheap Arm/Linux boards have USB Audio Class drivers?
do the cheap Arm/Linux boards have USB Audio Class drivers?
USB drivers consist of the actual USB controller driver, common USB core and the specific class driver. Of these only the USB controller is board-specific (or better SoC specific). Since the USB controller for these boards is supported in linux kernel, usb audio is just a matter of compilation of the appropriate kernel module for the target CPU architecture. In many embedded linux distributions (e.g. OpenWRT, DD WRT) the usb audio is just a question of a single installation command - downloading and installing appropriate pre-compiled packages holding kernel modules and user-space software. Some of the more powerful embedded boards run regular ARM port of debian linux.
You can find numerous reports of converting the Asus WL500 (MIPS) into a music player (OpenWRT, MPD, USB audio). A few years ago I played with it and it was no frills for a moderately advanced linux user.
With a PLL generated clock, would I2S offer any advantage over USB? Am i right that you could take this output and feed it directly to a DAC chip, allowing a much broader selection of DACs?
What is the advantage of PCI re: clocks. Are you suggesting changing the PCI clock to minimize jitter? or??
Nigel, AFAICT you seem to be describing stuff that linux / music player already does.
What is the advantage of PCI re: clocks. Are you suggesting changing the PCI clock to minimize jitter? or??
Nigel, AFAICT you seem to be describing stuff that linux / music player already does.
Well, the adaptive USB recovers the clock embedded in the usb stream, using PLL. That is in my opinion worse than just generating the clock via PLL from a stable crystal. BTW, the often acclaimed Asus Xonar cards generate their 44.1kHz clock via PLL too.
Basically yes. That is how sound cards operate - the PCI or USB chip generates I2S, fed into DAC chips. Plus usually a control of the DAC chip is needed (initialization, samplerate switching, digital volume control, etc.). For that I2C bus is usually used, available by the USB/PCI chips and on the embedded boards too.
The "soundcards" on the embedded boards have often the same functionality as PCI controllers of regular sound cards, just integrated into the SoC.
Not really, I am just saying there are easily available inexpensive PCI cards with technically optimal clock circuits - two separate crystals, no PLL. The advantage of such configuration is subjective to everyone, just as sound quality
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