Pc -> Dac, How ?

[ejaouen]

To me ADAT is the perfect simple way to do it, with the inherent bonus of electrical isolation between pc and dac.
The only thing still needed is a small diy board around wavefront AL1402G chip near exactly as described in its datasheet. This is very simple but still too complicated for me being a newby in creating circuit boards and soldering ICs.
I hoped the twisted pear guys would be interested in this project...

I will probably end up making it on a stripboard with a "soic to dip adapter" but this going to be a long task, knowing how fast and experimented I am...

 

[Telstar]

To me ADAT is the perfect simple way to do it
...

Isn't ADAT limited to 16/44.1k per channel?

 

[ejaouen]

44100 or 48000hz is the limit yes (if you want the 8 channel possibility) ; but you can have smux which doubles the hz at the cost of reducing the number of channels.
Personnaly I have hard time hearing more than 20000hz so 44100hz sampling is enough !

ADAT is 24 bit capable (not 16bit only)

So I do not see any real limitation in ADAT.
Would it be 16bit limited then yes ADAT would be worthless...

 

[Telstar]

44100 or 48000hz is the limit yes (if you want the 8 channel possibility) ; but you can have smux which doubles the hz at the cost of reducing the number of channels.

So, from a board like the RME with 8 ADAT channels you could have 2 24/192k channels (if you find a way to do that)?

 

[padam]

My opinion is that the DAC used&implemented is more important than the resolution, I am perfectly happy using USB.

 

[Hurtig]

Is this thread gonna end up with some construction, or just a lot of talkin???

 

[ejaouen]

Hi hurtig,
Design me my AL1402G pcb and discussion is finished ! (I prefer through hole components when possible) : many asking PC to DAC how will have the answer from you !

Bonus : AL1402G chip is inexpensive

Telstar :
All recent adat RME cards have smux working and I think there is a document on wavefront website explaining how to make their AL1402G ADAT receiver chip accepting smux. You can have four channel 96k or stereo 192k.

 

[lnekhamkin]

Status?

Is this thread gonna end up with some construction, or just a lot of talkin???

Same question here. Are we making any real progress after 6 months worth of conversation?

 

[mr.duck]

Re: Status?

Same question here. Are we making any real progress after 6 months worth of conversation? [/B]

How about using existing solutions and making the best of it? Like a pro USB audio interface (doesn't need to be expensive)... with optical spdif output. Just except that it's going to be jittery as hell and clean it up later like with a spdif or IIS reclock module. Optical is nice because it isolates things electrically.

 

[lnekhamkin]

The problem with this approach is to properly clean jitter, downsteam
device or devices will have to be expensive

 

[mr.duck]

The problem with this approach is to properly clean jitter, downsteam
device or devices will have to be expensive

Are you sure? There's the DDDAC spdif receiver; it claims to do spdif reclocking. There's also the twisted pear ASRC. If you feed it with 44.1KHz and resample to 44.1KHz then it should just reclock and pretty much remove all the jitter.

I heard that Emu USB soundcards do block transfer of audio. So that they also have to reclock the data inside the audio interface before sending it to the outputs.

 

[lnekhamkin]

Are you sure? There's the DDDAC spdif receiver; it claims to do spdif reclocking. There's also the twisted pear ASRC. If you feed it with 44.1KHz and resample to 44.1KHz then it should just reclock and pretty much remove all the jitter.

I heard that Emu USB soundcards do block transfer of audio. So that they also have to reclock the data inside the audio interface before sending it to the outputs.

I am not buying this. In order to properly do reclocking, one needs to have a sizable RAM buffer. Neither DDDAC nor Twisted Pair has it.
If this problem were easy, the solution would have already been incorporated into the $300 DACs one can buy on eBay. As to the EMU usb devices, they do not use SPDIF, and rely instead on USB bus, USB drivers and USB firmware.

 

[phofman]

I am afraid the RAM solution introduces very large delays which makes the DAC unsuitable e.g. for movie playback.
AFAIR DDDAC uses plain clock realigning which is not a bit-perfect solution (eventually a race condition occurs leading to sample loss) a no professional manufacturer can afford to use that (in the same leauge as NOS).
Twisted Pear uses ASRC which is technically the proper solution if the clock is already jittery.
In my opinion the best solution is keeping clock clean from the begining which is how E-MU USB cards operate. Their asynchronous USB mode avoids any PLL and reclocking.

 

[mr.duck]

I am not buying this. In order to properly do reclocking, one needs to have a sizable RAM buffer. Neither DDDAC nor Twisted Pair has it.
If this problem were easy, the solution would have already been incorporated into the $300 DACs one can buy on eBay. As to the EMU usb devices, they do not use SPDIF, and rely instead on USB bus, USB drivers and USB firmware.

Why does the twisted pear ASRC need a sizable RAM buffer? It's a dumb device... whatever sample rate you feed it, it will just spit out the data at it's own rate based on its own clock. I imagine it works very well but I don't know exactly how it performs compared to other devices.

Emu do use spdif. Take a look at Emu 0404 USB. It has coax and toslink spdif I/O. Here are some inside shots. I wonder if it is possible to tap I2S out to be fed into a higher quality DAC of your choosing. It has a custom made creative chip in there. Trying to come up with somthing better in a DIY capacity is going to almost impossible.

 

[KOON3876]

Hi I ordered AL1402G, small parts from Digikey,
LP2950ACZ-5.0NS-ND IC VREG 5V MICRPWR TO-92
DS1812-5+CT-ND IC ECONORESET 5V P-P 5% TO92-3
TORX177PLFT-ND MODULE RECEIVER FIBER OPTIC
445-1527-1-ND INDUCTOR POWER 47UH 1210
497-1751-5-ND IC HEX INVERTER 14-DIP

E-MU 1010PCI and EM8830 WordClock extention,
ART SYNCGEN WordClock generator.

If everything goes well I will report again.

 

[KOON3876]

Already there is nice KIT for ADAT receiver...
http://electronics.dantimax.dk/Kits/Digital_audio/11329401182.html

 

[daneman]

why muxing

hi,

i also think about using I2s optical for electric isolation.

i haven´t read the hole thread and this is a new topic for me, so forgive me if i haven´t catched something essential..
but, instead of using an optical converter muxing all channel to one (guess that´s what SPDIF does ), why not using a single converter for every I2s-line?

rg
daniel

 

[tritosine]

I think adat is no go without an ASRC like src4192. Therefore 88.1 , 96khz sampling rate is beneficial to use because pre upsampling with high precision going to serve the asrc chip better, and ALSO alleviate its own sound.

 

[tritosine]

Re: why muxing

hi,

i also think about using I2s optical for electric isolation.

i haven´t read the hole thread and this is a new topic for me, so forgive me if i haven´t catched something essential..
but, instead of using an optical converter muxing all channel to one (guess that´s what SPDIF does ), why not using a single converter for every I2s-line?

rg
daniel

toslink is a cheap multichannel format intended into consumer products, and there isnt anything else for multi channel. What you want is no cheap plastic connector like toslink but real glass like at&t , which are VERY cost prohibitive therefore uncommon, even then only used for spdif. There were some accuphase and wadia designs using ISO150 isolator IC by Burr Brown those make sense to me, but does it worth the added jitter? Maybe with multibit or switched capacitor output DA its no matter, wouldnt use it with PWM though.

 

[daneman]

thanks for that input, tritosine.

as i´ll feed my DAC by the PC, i expect a lot of HF-noise.. may cause jitter too.. that´s one of the reasons i changed from soundcards to an external DAC.