Anyone interested in a 5.1 decoder for a pc ?

[Modelworks]

I'm looking at putting together a decoder for pc usage.
It takes in an optical connection and outputs each channel at line level.
I also want it to have a headphone amp built in to the unit.

I've already roughly laid out the design .

The need for such a thing came from the problem I have been having with the pc adding noise onto the sound outputs , especially onboard sound and headphone outputs.

I could use a 5.1 receiver , but that is bulky, uses more power , and just wouldn't be fun

What I have so far is the decoder and the outputs.
Both are using Crystal audio chips.
One problem with this is that a unit that uses true dolby decoding can not be done by a consumer.
Dolby is not consumer friendly and requires hefty licensing fees to even look at chips that would decode to a true Dolby 5.1.

The unit I am constructing does not do anything other than split the stream into 6 separate channels. Output SNR is 115DB. 192Khz/24bit

The integrated headphone amp is where this unit really shines I think.
Specs so far:
Freq. response 10hz -20khz almost perfectly flat
Output power 200mW@32ohms, 85mW@600ohms
THD .0005% @ 600ohm, .001% @ 32ohms
SNR 130db @ 600ohms, 120DB@32ohms

headphone inputs are switchable between any of the channels.

anyone else interested in such a thing ?
I need to know before I decide to do a full pcb layout, etc.
If its just for me I can just perfboard the layout.

 

[geno]

Originally posted by: Modelworks
The integrated headphone amp is where this unit really shines I think.

That sounds awesome :thumbsup: no pun intended

 

[alcoholbob]

When you say split the stream into 6 seperate channels, does that mean just stereo x 3?

And what's the strength of the RCA outputs, when you say line-level do you mean it's good enough to be a true pre-amp or just a low level one like a sound card.

 

[ZetaEpyon]

Since you mentioned that true Dolby decoding can't be done, am I to understand that this would be taking 5.1 PCM and splitting it into analog outs, external to the PC itself?

 

[alcoholbob]

But how would you get multichannel output if it doesn't have dolby digital decoding?

 

[Modelworks]

Level of the output is low level but preamp can be added without too much work.
It is 6 separate analog outputs, all external to the pc.
So it could be connected to a dvd player and still produce the 6 channel output.

I can't call it dolby digital because its not using their certified software or chipsets.
Instead it is using chips that support AC-3 without the mention of dolby digital.
Kind of a way to do the decoding without having to pay license fees to dolby.

 

[alcoholbob]

I think the highest level burr-brown dacs go up to ~125db-130db SNR, thats good enough for reference level SACD playback.

The DACs are about $30 though, but if you put in a top shelf DAC I'm sure you can adjust the price accordingly.

But obviously if you are pretty far into the budget it would be too far of a swing right now.

Personally I'd be VERY interested in purchasing one depending on the DAC SNR because I am using a Yamaha receiver's DAC right now and it's not the greatest. The SNR is about 110db and has noise modulation/bit-error modulation around 1db. I'd love to get something that can do high quality audio sources justice.

 

[alcoholbob]

Found the list for Texas Instruments DACs

Burr-Brown PCM1791A 113dB SNR $ 3.00/ea
Burr-Brown PCM1796 123dB SNR $ 6.50/ea
Burr-Brown PCM1792A 127dB SNR $13.00/ea
Burr-Brown PCM1792 132dB SNR $13.65/ea

Good news the DAC is no where near $30 but its still not cheap.

SACD source dynamic range: 120db
DVD-A source dynamic range: 144db