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Bandwidth question?

I am interested in the qualitative difference in sound betw amplifiers that have -3db roll off at 100khz vs -3db at 300khz. Thru the amps I have tried, I suspect increased bandwidth has more openness and transparency and hence a better sense of space sharing. At the same time, it is easier to screw up the sound due to noise (from components/AC/RF) or improper cartridge loading. I am not very certain of the correlation and interested in what you guys think?

In reviewing the measurement sections of stereophile, many amps with -3db at 100khz demonstrate subtle rounding of the edges when reproducing 10khz square waves. I don't listen to square wave so I don't know what that translate into.

I realize that some amps (Spectral or Soulutions) has very high bandwidth (MegaHz) to implement negative feedabck. I am not refering to that.
128x128glai
martykl
3,578 posts
 
-3bd @ 100khz vs 300 khz can be critical - if you are a bat.
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tdaudio
201 posts
 
Al nailed it IMO. I can't think of any amp I have considered that had me worry about bandwidth.
hifihvn
943 posts
 
I just did a Google Search, and found this article. It's in a Positive Feedback, and it's surprising about high frequencies. Link.[http://www.positive-feedback.com/Issue52/ultrasonic.htm]
kijanki's avatar
kijanki
4,428 posts
 
I agree that most of us can hear only up to perhaps 15kHz but higher system bandwidth guarantees low phase shift. For instance my Rowland 102 amp has -3dB bandwidth of 65kHz but at 15kHz has phase shift of about -20 degree. Even at 10kHz it is still around -15deg. This phase shift affects sound (summing of harmonics). I would feel more comfortable with at least 100kHz bandwidth but agree with Al that bandwidth too high has problems of its own. Obvious problem is HF noise pickup but less obvious is increased chance of Transient Intermodulation (TIM) since reduction of the bandwidth at the input reduces TIM.
magfan
1,583 posts
 
I have a Sony ICF-2010 receiver which has a long wave band, from 150khz. and continuous coverage to 30mhz. this covers all the traditional SW bands and than some.
What I'm getting at is that if you have an amplifier with bandwidth to 100khz, you'll also need an antenna of suitable length. IOW, well over 6000 feet full wave for 150khz. much longer at lower frequencies. Submarines utilizing ULF for communications trail an antenna of some unknown but huge length. The transmitters antenna are huge arrays, visible from space.

I would suggest, however, that the bandwidth limit of 'd' amps is one of the subtle (or NOT?) problems people complain about.

Just by the numbers, I'd suggest a minimum of 2x upper human limit + a guard band....Maybe 44khz with rolloff above that of 3 or 6 db/octave. Now, I'm slippin' here, but where have I seen that number before? hmmmmmm.

Just thinkin' out loud.
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