ADAU144- as Digital Hub

Hi Brett,

This would be a rack mounted hub sending out to each monitor, is there facility on the software to justify the output left or right? also can the ADAU144x auto sense an input?

Im now unsure what to do with the ADAU1701 design that i have so much time into as well as help from coleman, The original idea was to make a DSP module that will allow the active filter networks of the monitor as well as differential analog input and a digital input.

Im new to all the digital stuff and didnt realise that there were different formats as well as the fact clocks have to be the same through out etc so my design now has chips to switch the clock when the digital input is used as well as conversion from Spdif to the 4 wire system the list goes on

Graeme

Hi Graeme,

The ADAU144x family would be a great solution for this problem, because it can take in multiple digital audio sources running at multiple sample rates and re-sync them to a single rate for output. There is also an integrated SPDIF receiver, so that covers the optical and coax SPDIF inputs. You could then use a USB audio to I2S converter and HDMI to I2s converter and so forth to supply data to the serial inputs. I think this will be a simpler solution than using the ADAU1701 because it requires fewer external components, even taking into account that you will need an external DAC.

Thanks

Brett

Hi Coleman,

I think that will be a good idea, I have messaged you in the ADAU1701 discussion, I will sort out a diagram of how the system will work and upload it first thing tomorrow.

I thought the spdif was a stereo signal but there is a justified left and right flag for the 2 halves of the source so if your using digital inputs on a pair of active speakers you must tell one speaker its left and the other right.

Graeme

Hi Graeme,

As we went down the design path for the ADAU1701, I don't think I knew the scope of the whole system! The ADAU1442 is a great solution for solving the problems as Brett lays them out, and it will have much more processing power than the ADAU1701 as well. You will need to consider whether you will receive signals in the analog domain, we can think about using a stand alone ADC if needed.

I am not sure what you mean by justifying the output left and right? The DSP has the ability to pick single channels out of a datastream, and it can process and route them individually if that is required.

Maybe we should take a step back and draw a block diagram of the whole system, detailing inputs and outputs, and how the pieces should all fit together. Once we have the blocks written out, it might be more obvious what pieces should fit into the puzzle. We can take this to a private discussion, if you do not want to show your design.

Coleman

Hi Graeme,

Yes, the stripping of channels out of the S/PDIF stream is no problem at all.

I look forward to seeing your diagram. I will add Brett to the discussion as well, however he is traveling for the next week or so.

BR,

Coleman

Just bringing this back to the top as i need to start looking into a digital hub as described in the original post, I'm now using the 1442 in the active speaker and i have a spdiff input .

Im looking for recommendations on chips for the HDMI and USB sections, I'm probably going to use another 1442 on this project and then output left justified and right justified spdif.

Im strictly only looking for audio from the HDMI and that needs to be 2 channel output

Any help would be appreciated

Graeme

I'm working on a similar project as well, but mine is complete overkill in comparison to what your trying to achieve. Mine is based on a pair of ADAU1442/5 and a pair of ADAU1966.

All Digital Inputs are going to be available on board edge for the DSP's, Spare DSP outputs are going to be routed to the side for an Digital Out board in case you want to experiment with different setups. The DAC's will have all 32 Channels of balanced audio on the other side of the board. Control will be through I2C ( Hifiduino).

USBi will be on the Digital Input board and tied into I2C bus as the DIX9211 will handle all the digital input switching. On the Output board a DIT4192 will be handling the digital output.

Good luck...

Thanks Dave,

Im only interested in the audio section of the HDMI, for some reason it seems to be used as a digital audio connector, i did look on the video section and it was mainly people asking video questions lol

I have looked but it i couldn't see any USB audio codec does AD have anything or even plan on doing anything?

The problem I'm finding with other manufacturers are that chips seem to be geared towards headphones rather than a general audio interface but i guess this is what the market dictates nowadays

Graeme

Hello Graeme,

Since here at DAU we only work with the audio converters and audio specific DSPs I cannot help you very much with the video parts. However, Analog Devices does produce HDMI parts and the ADV7623 looks like it would do the job you are looking for. By using this part number in this post it should trigger an email to the appropriate Applications support person. If this does not happen then go to the Video threads of the EngineerZone forum and post the question there. https://ez.analog.com/community/video

Thanks,

Dave T

Hi Graeme,

I'm curious, what do you mean by USB audio codec? Are you hoping to stream USB audio directly to the device and have it converted to analog audio? I'm not sure if there are many chips out there with that capability.

As far as USB audio streaming is concerned, I'm familiar with devices from XMOS: http://www.xmos.com/en/applications/audio

However, it's worth noting that these are all basically USB-to-I2C converters... There's nothing with an analog output that I know of.

Hi Yagami,

Already working with xmos for this project to do exactly as you suggest, i don't need an analog in just the I2S stream. Good to know i found a good solution though it looks like i will drop the HDMI interface as all the HDMI chips need a MCU to operate them and I'm not going that route

Thanks for your suggestion

Graeme

Whoops, small correction to my previous post. The Xmos chips function as USB-to-I2S converters, not necessarily USB-to-I2C converters (although some of them can do that, too!).

If I had a dollar for every time I mistook I2C for I2S (and vice-versa), I could take myself out for a nice dinner!!

Hi Guys

Im starting on the schematic this week but i have a couple of questions

The Hub will be based around a 1442 so with this part defined i am curious if i will need other conversion chips to receive separate inputs from:

AES/EBU

Toslink SPDIF

Coax SPDIF

I then want to output 2 SPDIF signals one Justified Left and the other Justified Right can i do this in the DSP or will i need outboard chips

Graeme

Anther question, can i run a 11.2896 MHz clock? the XMOS usb requires this clocking speed and i would like to keep the number of system clocks to a minimum

Thanks

Graeme

Thanks Coleman, is there any disadvantage to running at 44.1 rather than the 48? the other option on the clock for the xmos is 24.576MHz

Could some one let me know if i need any other codecs in response to my previous question in order to get my signals in and out of the 1442?

Graeme

Hi Graeme,

From page 8 of the ADAU1442 datasheet, MCLK must be between 3 MHz and 25 MHz, approximately. Your MCLK will yield a default rate of 44.1 kHz.

Cheers,
Coleman

Hi Graeme,

There's no real disadvantage to running your system at a slightly lower sample rate. It simply lowers the audio bandwidth by a small margin. Still, 44.1 kHz is CD-quality. I don't think that small 10% reduction will be noticeable to anybody!

When you change your sample rate, be sure to follow this tutorial in order to make everything behave properly!!

FAQ: How do I change the sample rate of my SigmaStudio system?

Regarding your question about AES/EBU, Toslink SPDIF, and Coax SPDIF...

The ADAU144x only has one S/PDIF input pin, and it takes two channels of audio, un-encoded, which follows the S/PDIF consumer standard. It has no decoding functionality.

If you only need to get one input at a time into the DSP, you can use an external switch in your system to select the source in hardware. That's easy!

Remember, this won't work with encoded audio data! It will only work with raw PCM.

However, if you need to take multiple S/PDIF inputs simultaneously, then you'll need an external IC that can take S/PDIF input and generate an I2S output.

Additionally, remember that your S/PDIF source(s) are asynchronous to the ADAU1442. This means you will need to use ASRC(s) to re-synchronize the audio to the local ADAU1442 clock.

Hi Yagami

I want to run all the spdif inputs together, i don't like users needing to select switches so i guess i will need to use spdif receivers. Does any one have any recommendations?

As far as clocking goes i want to use an oven controlled oscillator so if everything is being reclocked by the 1442 then i guess as long as this has the precision clock i can use regular oscillators for the other clock sources.

What about my output? the 1442 only has a single spdif out and i need 2 so will i need to use a spdif receiver on the output as well?

Many thanks

Graeme