Digital potentiometers and YOU

[Life of Brian]

In Ben's latest C64 laptop, he used a digital pot for his audio amp. This enabled him to use two buttons to control the volume instead of a slider or dial. In my opinion this is a far superior setup for a portable with a manufactured case. I emailed Ben a while back with questions about how he constructed his, but he has not responded. Therefore, I turn to you. Do you have any links, tips, or info for me about building an audio amp with a digital pot to control the volume? I've done some searching, but haven't found anything particularly useful or understandable yet. I'd appreciate any help you can provide.

[snowpenguin]

I believe there are premade parts that do this, somewhere.

[Life of Brian]

I seem to have already found something:

http://www.aaroncake.net/circuits/volume.asp" onclick="window.open(this.href);return false;

http://datasheets.maxim-ic.com/en/ds/DS1669.pdf" onclick="window.open(this.href);return false;

Thoughts, suggestions?

[snowpenguin]

Looks good, nice and simple, a capacitor, the chip, and two buttons, nice. If you build it, make sure to let us know how it works out and post a picture of the completed circuit please!

[Life of Brian]

Looks good, nice and simple, a capacitor, the chip, and two buttons, nice. If you build it, make sure to let us know how it works out and post a picture of the completed circuit please!

I will. I am still looking for input from someone who knows more about this, though.

Edit: Okay - I think I'm going to go with one of these (DS1669 digital pot) with one of these (TDA7053A stereo amp). My goal is to minimize the number of parts needed, and it looks like these fit the bill.

[Life of Brian]

Here are the actually important parts of the spec sheets I listed above, for those of you too lazy to click on a PDF link:





The neat thing is that both ICs can run off of 5v, which is convenient because my screen and SNES are running off of 5v as well. The amp is already stereo, so that's one less step for me.

Here's some input from Mario about controlling the volume levels:

Looking at the datasheet, there are two ways to set up volume control. One requires less parts but has a lower maximum gain of 34db. The other requires more components but has 40db gain. Choose based on how many parts you want to use or what parts you have. I'm not sure just how much of a difference 6db will make, so I suggest trying both.

So in both cases pins 2 and 8 are connected. The pinout says these are the DC volume control pins for the left and right channels. By combining them, you can control both channels at once. (Obviously, what you would normally do.)

The unlabeled pin on top of the IC is Vcc (positive power) and the bottom ones are ground
So you'd connect pins 2 and 8 together and hook it up to the other components accordingly.

Hope that helps!

^He was kind enough to answer some of my questions a week or so ago in a PM I sent him.

Hmm, I think this is quickly turning into another tutorial...