Caveman question about DAC, ADC and possibly skipping the ADC all together for testing wireless speaker connectivity

[Pete Lee]

Hi folks,

I am quite new to hardware engineering in general, but wanted to get a "best guess" on what you'd do if you were in my shoes...

In what I'm hoping is a "not super expensive" sort of experiment, I'm hoping to hook up a pair of Elac Uni-Fi UB51 speakers to some wireless audio dev boards I have.

1. The wireless surround audio dev boards I'm using (publicly accessible datasheet link) have a PCM5102 DAC and a WM8782A ADC (datasheet). I can reconfigure the boards to be either a Tx or an Rx.
2. In my case using the DAC for the Rx is going to be the most feasible.
3. I will be getting a MiniDSP MCHstreamer kit board that I can use instead of the ADC to directly stream eight channels audio from my computer over USB into the Tx board via I2S (only two are necessary in this case).
4. One of my engineers noted that our dev boards have more than enough line input drive voltage to directly connect to the Modulus-86 10th Anniversary kit I purchased. Volume controls are handled at the Rx boards, so I don't need any sort of gain controls (and we strongly prefer audio inputs that are not preattenuated).

I'm wondering if there is much in the way of tangible benefit using I2S instead of a line input into the ADC. My extremely loose theory:

• Getting rid of one conversion element might help increase the ability to assess the quality of the wireless audio connection itself.
• Alternatively (and with care), I'm wondering if this might help avert issues with interference since the line-in is unbalanced (headphone jack) since I'm staying in the digital domain.

Thanks, in advance, for your ideas!

 

[beeface]

I think a caveman would be more interested in how to use a DAC as a weapon, shelter, etc.

(sorry, can't help you)

 

[RandomEar]

I'm not quite sure I understood the signal chain correctly, but I assume that it looks like the following:

MCHstreamer {i2s} -> dev board 1 {wireless} -> dev board 2 {line out} -> Modulus-86

If so, I see no reason why you would use anything other than a digital connection from the miniDSP to the first dev board. i2s is digital and works fine here. The ADC and DAC on board 1 should be unused in that case and it just acts as a fully digital wireless bridge. The DAC on the second, receiving board will then convert the signal to analog and drive the Modulus-86.

Overall, this looks good. You should check the output impedance of your dev board line outs and the input impedance of the Modulus-86, just to be in the safe side. The ratio should be 10/1 (input/output) or better, otherwise you may end up with an altered frequency response.

 

[somebodyelse]

Sorry, but I'm not signing up to dropbox to see a datasheet.

I'm confused here - surely your engineers have assessed the dev boards already, including the performance of the onboard ADC, DAC and the wireless link alone (i2s in to i2s out). That's the sort of detail I would expect to find in the documentation if I was trying to evaluate your product using your dev boards.