On 04/02/2011 14:20, Jacopo Monegato wrote:
> Hi there!
> I wonder if the tag is the most appropriate,
> as a student (and musician) I often wonder about making my own equipment,=
 and i have been thinking for some time to build, or just to design, my own=
 audio interface.
> Let's forget about all the analog part for a second. After all that stuff=
 the signal would be converted into digital, then written into a pic and th=
en sent through the UART to the pc, using usb protocol. A teacher of mine s=
uggested to buy a 5$ 5.1 audio interface from the internet, then change the=
 ADs, but i wanted to do the most i could on my own.. i mean, it can't be T=
HIS HARD to program a pic to encode the data from the AD to match the USB A=
UDIO 2.0 driver requirements..
>
> My problem is here: i tried to search over the net for the driver specifi=
cation but i'm not sure to have found it out, could anyone push me in the r=
ight direction?
>
> Jacopo Monegato
>   		 	   	=09
What do you want to do that a decent off the shelf USB interface doesn't do=
?

I have this. It's very old.
http://www.xbitlabs.com/articles/multimedia/display/creative-sbmp3.html

I can open it and tell you what chips it uses. I think from memory at=20
least part is made by Analog Devices.

Most of these it's not  the ADC /DAC that isn't good enough. Just poor=20
packaging and analogue stuff. Buy a Creative USB SoundBlaster MP3+,=20
disconnect the analogue I/O at the DAC/ADC chip and put it in a larger=20
box with jacks/XLR and analogue interface of choice.

Buy a couple of different ones and identify what it is that you can do=20
better.

A PIC with USB slave port still needs decent ADC/DAC. You'll not handle=20
very high sample rate  + bit depth + number of channels on 18F=20
certainly. For seriously more "oomph" you'll want higher end ARM or MIPS=20
(The high end PIC is MIPS I think).
You may find the Analog Devices chip used in Creative MP3+  is fine.

See also Sound Blaster Extigy

and
current product

http://us.store.creative.com/Sound-Blaster-XFi-HD/M/B004275EO4.htm

There a "professional" products that are very very good. Usually=20
Firewire, but some USB + XLR

I have installed very nice Firewire enabled mixing desk that "records"=20
all channels.

--=20
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