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Topic: audio channel select and volume control (Read 3046 times) previous topic - next topic


Jan 17, 2013, 12:33 am Last Edit: Jan 17, 2013, 12:55 am by Krodal Reason: 1
What chip is available for a audio channel select and volume control ?
Some chips are hard to get.

I have made a FM radio with the TEA5767 (noisy, not sensitive, medium sound quality), but now I want to combine it with other audio sources. I want to select between 4 sources but a mixer for all channels would very nice, or else just one volume control.

The CD4066 could be good enough to select the channel. But I also need a volume control. The quality has to match the good quality of my computer soundchip (ALC889A).
What chips are available ?



This is what I found so far.

The DS1802 is a I2C stereo log digital pot, but hard to get and costs 15 euros.
The PT2258 is a 3 channel stereo mixer and is very cheap (1 to 2 euros), 5 to 10V.
The AD5206 is hard to get.
The LM1971 is a single channel attenuator, costs about 7 euros.

If I use the PT2258, I need two of them for a mixer for 4 stereo channels.
The I2C address is selectable, so they can be used together on the same I2C-bus.
Is the chip any good ? will it work at 5V ?


Can't help on this, I get couple this https://www.sparkfun.com/products/10613?, though haven't try yet.


I read this: http://arduino.cc/forum/index.php?topic=12262.0
So the PT2258 is not a mixer, and I don't know how to connect all outputs together.

So I need something else.


Jan 17, 2013, 09:39 am Last Edit: Jan 17, 2013, 10:11 am by Krodal Reason: 1
The PT2258 has 6 (3 stereo) seperate channels and seperate outputs.
So I could use resistors at the output and connect them all together.

Will those resistors have influence on the high frequencies, or is this very low with metalfilm resistors ?
The resistors connected together reduces also the signal, so I have to amplify it.
If I have to filter the 5V, it could be a little below the minimum of 5.0V, so I might also need an extra power circuit for it.

Is there something simpler, like a complete digital mixer in one chip ?


Digital Mixer... Yes a CD4052 will give you a dual 4 channel audio selector and an LM1036 (sampled from TI/National) will give you a DC operated Vol, Tone and Bal control IC. It's a plan I intend to implement. Is a copy of the sketch you have for the 5767 available?. I bought 2 of them yesterday, one to play with and one to use. The only other requirement you will have is some buffer amplifiers as the tone control IC wants to see 1V levels as I remember. NE5532's should work well there and I have a lot of them. I've attached data sheets for both IC's and the for the LM1036 the volume control can be used W/O the other stuff...

--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard


Thanks, the channel selecter seems very easy to use.
I was hoping not to use an opamp or at least a 5V opamp.


Yeah, I would like to have done it easier than that but I am doing to use the LM1036 anyway so this makes my audio processing one block and I may use a switched switcher for power too. There are OLD Skool tricks like capacity multipliers that make those devices perfectly workable to several amps with only Vcesat heat losses where the losses are largely ohmic and thus small. But the chip works and could even be PWM'd (with careful filtering) as the control voltage is under 5 V. and there isn't a simple attenuator for stereo audio that I've seen that is as easy to use as much or as little as you choose of. Sometimes there are choices and there are 'choices' the hardest part is finding the best long term choice.

--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard



Do you have any updates on this project?


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