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Wide Bandwidth Amplifiers Problems

I am not very tech savvy but am trying to understand what the drawbacks are to wide bandwidth amplifiers, are they prone to some sort of distortion or interference and how can this be avoided? Not sure if it's possible but there was one post saying a wide bandwidth amp picked up a radio station, I would not want that and I dont see how you would prevent that! What's possible/how to avoid? Thanks 
norany
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erik_squires
16,400 posts
 
With the wrong interconnects in a bad place you can pick up a radio station even without a wide bandwidth amp! :)

So the theory is that a very wide amplifier is very fast, and can go very low, perhaps to 0Hz and 100kHz.  The problems are that 0 Hz is a DC signal which can blow your speakers, and 100 kHz could fry your tweets if amplified and you'll never hear either.

So, sure, wide bandwidth amps are extremely capable in the audible zone, but does that alone make it better?  Meh.
atmasphere's avatar
atmasphere
11,962 posts
 
So you are saying don't fall for the claim wide bandwidth is bad?
Wide bandwidth is used to maintain phase relationships within the audio passband. To do this they have to go from 2Hz to 200,000Hz; 1/10th the lowest frequency and 10X the highest frequency to be amplified.


The exception to this is if the amplifier has a very high amount of negative feedback, in excess of 35dB. In this case the bandwidth can be limited to just about 20KHz, and the feedback will allow the amp to correct the phase that would otherwise be present by a rolloff just outside the audio band.


Radio Frequency Interference is another matter altogether. Its caused when a strong RF signal gets rectified somehow in the audio circuit and gets amplified. As others have pointed out, wide bandwidth isn't needed for that to happen.


So don't fall for the claim that wide bandwidth is bad.  
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