TOPIC:

Hello,

at my current 3/4-way project, I thougt it would be best to place the MiniAmps in each speaker, to have short connections to the speaker drivers.

So it would be best to have a nice box in my hifi-rack, with miniDIGI 2xminiDSP, powersupply and attenuation, and the miniAMP built into the loudspeaker Cabinet.

Questions:
1) Does this make sense at all?
2) How long can I make the I2S Connection cables?
3) Should they be shieldet in any way, perhaps use cat.5?
4) What other pins have to be connected?
5) Would It be better to have one powersupply in the DSP-box, or an individual one at each speaker?

Thank´s in advance,
Daniel

Hello Daniel,

Nice project you seem to be working on...

In answer to your questions:
I2S is not meant to be run for long distance but only board to board/PCB connection. Running long distance with a cable wouldn't be a good idea for 2 reasons, signal integrity (there are some high speed clocks which would look terrible after being run on a cable), drive strength of the IC pin, not meant to run a cable and therefore could do un-expected things on that side too.

So although this idea sounded good. It's not possible.

Hope this makes sense,

Is it possible to use miniDSP in a I2S config. with the I2S signal from a in-car CD player?
I assume the cable lenght will be no more than 20-30cm if miniDSP is to be placed near CD player itself.

Cheers

Kamyk,

It's hard, if not impossible to answer your question definitely without knowing the environment. As said earlier on, I2S isn't meant for long distance. It's just for short board to board connection and in our case, being used in a very controlled environment (on the boards we designed and on short distances).

If you were to use an I2S signal from your CD player, do you know if this device is an I2S slave or Master? I guess that would be the first thing you'll need to investigate. As mentioned in the I2S tech notes, miniDSP is master by default, although it could be changed to Slave, it requires more work and still need to make sure that the I2S Clocks + MCLK are synchronized.

So maybe as mentioned in the tech notes, I'd recommend to do some reading to make sure that:
- your i2s signal is going to be compatible with the miniDSP (not always the case and not as simple as saying it's an I2S signal since there is a whole range of clock combination)
- if you go with this setup, we just can't guarantee that it will work for sure since you're in an environment (car audio) that is noisy, and using the board as a DIY electronic project so would first need to be fluent in electronic to understand what's going on. Hope you understand that we can certainly support you on miniDSP products, but to some extend. If you're trying to combine them with other products and going for a full blown DIY electronic project, that's out of our control. I'm not sure of your electronic understanding but you mayl have to do your homework first (in learning more about I2S) to make this happen.

Hope this makes sense,