Those are the same things that they use in doctors offices and other places. There is a lag in volume as it takes quite a while to determine it should come up or down. Can be annoying and I didn't see a time control on the front. Still that would do what you want very well.
A question for audio engineers
What does it mean, volume lag?
Imagine that when it is too quiet, it will take say 5 seconds to come up to volume and visa versa. Since the change in volume of the material drives its automatic gain control (AGC), it can not work until the change on the input side has happened. To keep the dynamics of the music from causing it to "pump" (where it sounds like someone turning the volume knob to the beat), it has a long delay on the volume control. If you look at compressors (a similar item) there often are controls for attack and decay which sets how long it takes for the compressing action to take place. The manual for this doesn't mention the numbers for this device, but I would have to guess a few seconds otherwise it could get false readings from drums or the like.
Well that's a red check mark, then.
Originally posted by Sir HC:In general, the biggest limitation on just about all AGC algorithms I've worked with is that they choke whenever the input signal goes to zero. They normally work by using a feedback control system where average power is measured over a period of time and making an adjustment to the gain level based on how the average power compares to the target power level. If there's a gap in between songs coming out of your MP3 player, there's very little power in the signal during that time, and as a result, the amplification level can get turned way up. When the next song starts, it can be very loud and painful on the ears or even damage equipment.
Imagine that when it is too quiet, it will take say 5 seconds to come up to volume and visa versa. Since the change in volume of the material drives its automatic gain control (AGC), it can not work until the change on the input side has happened. To keep the dynamics of the music from causing it to "pump" (where it sounds like someone turning the volume knob to the beat), it has a long delay on the volume control. If you look at compressors (a similar item) there often are controls for attack and decay which sets how long it takes for the compressing action to take place. The manual for this doesn't mention the numbers for this device, but I would have to guess a few seconds otherwise it could get false readings from drums or the like.
Setting slow attack times or fast decay times can help make it less of a problem and it's unfortunate that the 422 device doesn't have any controls for that. That could be the default setting like Sir HC described so maybe it's not even an issue. There are controls to limit total gain and total output voltage, however, so your other equipment will at least be protected from voltage spikes.