And this one's got me puzzled, maybe someone out there could shed some light on it?
Here's what I'm building: I need a microprocessor controlled, differential audio signal attenuator. Basically, the user can set a timer with some BCD switches (read by my ATTiny2313). When a song starts playing, an external interrupt signal goes high, which starts a timer countdown based on the values on the switches. When the timer hits zero, the ATTiny uses a SPI interface (or something similar) to control a digital pot to attenuate the audio signal. Sounds simple, but I'm having a horrible time finding an audio attenuator. I was going to use the MAX5410, but the audio input has to be within DC range (0-5VDC) and non differential. My audio signal is a differential audio signal (R+,R-,L+,L-, and GND) that is 1Vp-p, so it would be out of range. Here are a few options I've found, can anyone shed some light on which one would work best, or give me another idea?
1 - Use the MAX5410. Since the MAX5410 has two channels per chip and the SPI can be daisy chained, just hook two 5410's together, so one 5410 attenuates R+ and R-, and the other attenuates L+ and L-. Hook up an op amp to the audio inputs to bias the signal up to DC ranges.
Problems: The output will then be biased, so I'd have to de-bias the output using ? (capacitor high-pass filter? another op amp?). The differential signal will be attenuated separately, which could introduce noise, or basically defeat the whole purpose of a differential signal.
2 - Use a differential chip. I've found one so far, the MAXIM DS4420. That fixes my differential problem, but the input still has to be within -0.5V to 5VDC. Is that cutting things too close?
Problems: Might be outside spec to put in a 1Vp-p signal, do I still have the need-to-bias-and-de-bias problem as I did with the 5410? This chip only attenuates 35db, not down to mute, which is what I want, but I could put two chips in series to get the same effect?
Any help would really be appreciated, and I can provide more details upon request. (Also, if you know of a better location for me to post this question, I'll be happy to move it)