Looking to build digital audio interface

[lowball]

I'm looking to build an audio interface for integration into nuendo, pro tools, etc.  I dont even have a clue where to start but would like to learn the sciences behind the functionality and processes that make it work, along with having a nice piece of gear available at my disposal.

Looking to build idealy something with idealy

192khz /32bit support,
at least 4x12 analog i/o
fairly high quality da/ad converters

then there's the software/drivers side which I have zero knowledge about, I can have my friend write these for a small fee.

anyone ever done something similar to this?
would love to discuss this and see if we could come up with some sort of schematics to test out.

cheers

 

[jdbakker]

http://www.groupdiy.com/index.php?topic=35486.0

JDB.
[and please read http://www.groupdiy.com/index.php?topic=33355.0 ]

 

[Andy Peters]

I'm looking to build an audio interface for integration into nuendo, pro tools, etc.  I dont even have a clue where to start but would like to learn the sciences behind the functionality and processes that make it work, along with having a nice piece of gear available at my disposal.

Looking to build idealy something with idealy

192khz /32bit support,
at least 4x12 analog i/o
fairly high quality da/ad converters

then there's the software/drivers side which I have zero knowledge about, I can have my friend write these for a small fee.

anyone ever done something similar to this?
would love to discuss this and see if we could come up with some sort of schematics to test out.

cheers

FireWire, USB, PCI or PCIe?

-a

 

[Moses]

Just to put it into perspective, Im probably going to be building a 48k 16bit AD/DA for my Honours project at uni... And it will only be stereo.

Which makes it a daunting project to attempt in your 'bedroom' (for want of a better description!)

Mo

 

[Tubemooley]

This is a pretty heavy duty project. But if you're doing it for your Honours project, then it sounds like a good idea. I would recommend this...... Build the 48k 16-bit AD/DA box. But leave the "source" as an existing entity. In other words, you're building the AD/DA converter box. But define your project so that the digital data will go into and out of your box via S/PDIF or AES connection. Then, you have a PC with a sound card creating the S/PDIF signal and it's got it's own driver and will interface with the recording apps like Nuendo and PT. Designing a sound card which is either PCI or PCIe or USB or Firewire...... That is a huge project involving lots of hardware and software. I think that would be too huge a project for your Honours project. See what I mean? But building an AD/DA converter box.... That's do-able. Start googling on "diy ADC" and "diy DAC" and stuff like that. I've been doing that for at least 5 years now. There are a few projects out there with very good descriptions and schematics. For instance, google on "Beis ADC". You'll get this guy named Uwe over in Germany. There are at least a couple of threads about his project here on Prodigy. I think he posts here periodically. Anyways, go look at his project. Yes, he's selling boards and kits and stuff. But he describes what the board is and how it works and the circuit modules and schematics too. Go look at as a first step. Where are you located? Dana Walcott.

 

[Moses]

Yes, sorry! I wasn't very clear, the Honours project is just an AD/DA no computer interfacing (as far as I'm aware!!). Got a few ideas up my sleeve that probably won't work regarding the analogue stages, but I really want to go high end with them and trafo balance the outputs according to Walt Jung's work flatting the output response of an o/t...

Anyway, sorry for the highjack... Just thought that Andy would like to know that what he intends to do is within or perhaps beyond the scope of an Honours degree project...

 

[Tubemooley]

Moses.... That sounds good. Think about it this way - There is the digital section. Transmit and receive the digital data to and from the "sound card" source. And then there is the analog section. Coming off the DAC output pins or going into the ADC input pins. Everything "outside" of those pins is your analog circuitry. You probably already knew this. And then a power supply too. Implementing really good DAC's with discrete analog amplifiers and output transformers is not too difficult. Not that easy but not incredibly difficult. Implementing the ADC's is harder. I would say much harder. Those ADC inputs are nothing to laugh at. That's a very complex input right there. Go read the data sheets on the ADC IC's and start to get familiar with how they work and what they want to "see" from the analog circuitry feeding them. Most of the manufacturers put example circuits in the datasheets for what to build in front of the ADC inputs (same with the DAC outputs). Those examples will work. They definitely will work. But they aren't as good as we would want. But they will give you a starting point. Here are the big boys - Burr-Brown/Texas Instruments, AKM Semiconductor, Cirrus Logic (formerly Crystal Semi for the converters) and Analog Devices. Then you need to decide if you want to use a codec which has ADC's and DAC's in one device. Or use two separate devices. One ADC and another DAC. Choices, choices, choices. DW.

 

[compactaudio]

Some up-to-date technology:
http://www.thatcorp.com/datashts/THAT_1570_Datasheet.pdf
http://www.thatcorp.com/datashts/dn140.pdf

 

[mhelin]

This project gives a nice look into audio interface design:

http://openhpsdr.org/wiki/index.php?title=JANUS
http://openhpsdr.org/wiki/images/4/46/Janus-DCC-2006-paper.pdf

They first used FPGA with USB interface (KNJN Xylo board with Altera FGPA) and then later went for the custom bus design for the particular application. The "sound card" is not meant to be used with PC but with the specific Software Defined Radio (SDR) hardware.

It would be a good idea to first get the Xylo board and use the archived software from the Janus project (it's stored in their SVN repository svn://64.245.179.219/svn/repos_sdr_hpsdr/trunk/VK6APH and svn://64.245.179.219/svn/repos_sdr_hpsdr/trunk/KD5TFD/Xylo-Archive download first tortoise svn to browse the repos, some stuff is also here: http://openhpsdr.org/svn_archive/KD5TFD/ ). The you can just transfer the design in Verilog/VHDL to other interfaces (like PCI, PCIe or Ethernet, nothing wrong in USB 2.0 either) using the same FPGA platforms.

The KNJN boards are sold here:
http://www.knjn.com/eu/ShopBoards_USB2.html (EU)
http://www.knjn.com/ShopBoards_USB2.html (US)

While you are there notice the oscilloscope project (http://www.knjn.com/Flashy.html , I'm going to build one).