Audio Switch help?

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Audio Switch help?

Post by Xmodgeek » Tue Oct 20, 2009 9:43 pm

Hello, I've been working on a 4 input audio switch for my car. I've had some luck with making one out of lots of transistors such but for the 7 switches it's kinda impractical. So I've looked for a IC or something to do it all in one package. I did find a nice chip that would be perfect, that is if I had any idea how to control it...

The Chip is a TEA6422 ... ea6422.htm

I'm guessing I'd need a microcontroller or somthing but not sure. Any help would be appreciated or maybe a chip with out serial controls. Thanks

I'll post the drawing I have tomorrow hopefully if I can get to a scanner.

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Re: Audio Switch help?

Post by SETEC_Astronomy » Wed Oct 21, 2009 7:51 am

It appears you would need at a minimum an I2c controller, likely in the form of a microcontroller. In the past I've used a 4066 to switch audio and video sources and it requires only a High signal to the corresponding switch input. Perhaps someone here with more technical knowledge than I have could explain why that's a bad idea (or a good one).

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Re: Audio Switch help?

Post by MrAl » Wed Oct 21, 2009 1:02 pm

Hi there,

Yes it looks like you need a chip that can send out the address and data depending on how you
want to control the audio switching. It looks like the chip would send out the address first
followed by the data although they are not too explicit about that on the data sheet.
You can use any micro controller chip though even if it doesnt specifically have serial
capabilities built in.
For experimenting, you could also try using two switches, one for the Clock and one for
the Data. This could work because they spec the clock frequency down to 0 Hz.
The Clock switch would have to be debounced however, but not the Data switch.
You would use this by setting the Data switch to whatever value is needed, then
press or switch the Clock switch so that it generates a single pulse. You would
have to clock 8 address bits followed by 8 data bits to try this, for a total of 16 bits
by hand manually so it would take about 30 seconds probably but at least you would
get some idea how you need to send the signals. After you've done that you could
use a micro controller to generate all the signals, and perhaps have it read your input
switches to automatically set what modes you want the chip to switch to.

I kinda like the analog switch idea from SETEC_Astronomy too which doesnt require
a micro controller just to send the signals to the chip with. You could use a few
switches to get the control you need. What i dont know yet though is exactly how
you really want to control this chip...does the system really have to be controlled
automatically for some reason or can you use human operated swtiches to set all
the modes and change when needed? You'd have to answer that question.
To find out if the audio quality would be as good as the chip you've selected
we'd have to do some tests probably. The nice thing about this chip is that it
is spec'd for distortion too, and if the audio signal stays below about 2.8vrms the
distortion looks to be very very low.

The input caps shown on the data sheet can probably be 0.1uf but 0.22 might be better
if you are after good audio for a good sound system. You could test the frequency
response and if it doesnt go low enough then increase the capacitance as needed.
You could do this with one channel just to test for the right capacitance.

That data sheet is pretty limited on the information it conveys. I have to wonder if there
might be a better data sheet somewhere too.
LEDs vs Bulbs, LEDs are winning.

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