want to build a hd portable recorder.

You can probably do it as follows:

AES/SPDIF inputs -> SC939-06 transformer (sorry Jocko) -> CS8414 -> Microchip dsPIC w/codec interface -> hard drive. You'll also need the appropriate power management stuff (+5V/+12V supplies, battery charging, etc) to make a true 'portable' application.

My only worry is that the HD won't be fast enough - you'll need a FIFO in the dsPIC which is big enough to not overflow when you're waiting for the HD to finish a write, and the dsPIC doesn't have a whole lot of memory. An external SRAM could hopefully take care of this.
lagoausente said:
Gmarsh, is difficult to do this? What about writing the codec sofware? and what about the price aproximatly?
The Edirol r-4 costs around 1500 $.
The building of my own recorder would must be cheaper and not "two years work" of course. Let me know.
The price? hard to say. You could probably put all the required chips and passives on a PCB for ~$100-ish. Then you're paying for the hard drive, enclosure, batteries, etc...

You'll have to design the schematic and PCB, write the dsPIC software for writing to the HD in the "right places" (not overwriting existing files) - which involves writing it in assembly code unless you want to buy a C compiler for the dsPIC... build it, verify it works (again, i'm not sure if the dsPIC has enough RAM to buffer a stream to the hard drive)... possibly build another board from scratch using a 'proper' DSP chip if that didn't work... the list goes on.

It's not an easy "throw chips together" project like a basic DAC...

pinkmouse said:
I wonder if you could hack an iPod?
The iRiver IHP-120 already supports optical SPDIF recording... I have my doubts it's 24/96 capable though.