remote controlled volume with avr

[victor]

I have an old amp that has no remote control, connected to a directv box. I basically want to control the volume without getting out the couch.

I'm open to any other suggestion or approach, but this is my idea. I already played with arduino IR library and it was pretty easy to use a IR module. So I could use an atmel 328 or similar to decode the button press from a remote control, and control the volume.

I want to control the input level before it goes to the amp input, so I don't have to modify the internal amp potentiometer, something like this.

I could use a servo or digital pot.


But to be able to control it using a uC I think digital potentiometer is the way to go, but I have no experience with then, and how many circuitry is required for it to work.



Anyone can help me to build this circuitry. I want build something cheap that does the job, I know how to etch pcb and sodder smd, but through hole is preferable.

Any thoughts would be more than welcome.

[Alana]

Digital potentiometr in google and look at datasheets.
For example https://www.sparkfun.com/products/10613
And for volume control you would want logaritmic characteristic of a pot.

[tszaboo]

Ti has a series which is designed for audio use, mainly for preamps:
http://www.ti.com/product/pga2310
It is easy to use, not cheap though.

[garak]

Digital potentiometr in google and look at datasheets.
For example https://www.sparkfun.com/products/10613
And for volume control you would want logaritmic characteristic of a pot.

Alana's suggestion isn't bad. These devices are reasonably easy to drive (they use an SPI interface) and aren't too expensive. You'll need two for doing stereo volume control, but these DON'T feature zero-crossing detection and you may get a zipper-like sound when changing volume. It might also make sense to get a dual-channel model as the potentiometers in these will be more closely matched than two single ones.

Have a read of the comments section on the SparkFun page, there are a number of people there who are doing the same thing and got it figured out. You'll find all the SPI commands you need in the datasheet, specifically on pages 47 and up.

[Psi]

You could also use a motorized pot, like they have in some stereos/amps.
Generic H bridge driver on the mcu could control the motor speed/direction easy.