vivkr wrote on Oct 6th, 2008, 6:00am:Hi,
The primary problem is the very wide range of the audio bandwidth (20 Hz - 20 kHz). One would need a regulation loop which has a time constant large enough that the 20 Hz signals pass through, which would imply that the loop takes around 100 ms to react to a transient. With some simple models, I could get the system to achieve reasonable convergence to final gain values in 200 ms, but this would probably be too large a time, and also there is likely to be considerable distortion of the signal in this time.
Hi Vivek,
I do not see significant drawbacks in using AGC amplifiers for an audio signal. I imagine you could simply control the gain by looking at a threshold (at which the signals might be clamped) and trying to get the signal peaks as close to them as possible by adjusting the amplifier gain.
However, I do not see why you would need loops with such slow time responses while you could have the AGC amplifier with BW larger than the max frequency (20KHz in your case). I might be missing something I guess.
Another thing you might want to consider is the offset contribution from the AGC amplifier, which will change according to the selected gain. This at some point in time might hurt you and force your output signal to reach the clamp levels because of a large offset rather than a large gain...
Just a few considerations I came up with
Regards
Tosei