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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
atmasphere's avatar
atmasphere
11,846 posts
 
Marakanetz, as I mentioned earlier, it does not seem to matter that the speakers lack the bandwidth of the amps. The phase shift that will occur in the amplifier due to bandwidth limitations is something that you hear well within the range of human hearing and nearly any speaker can reproduce it.
learsfool
1,215 posts
 
Don c55, nice link. I can't find the articles anymore, but it has been proven in the last twenty years or so that the human brain does definitely detect frequencies above what the ear can hear, scientists just don't understand exactly how yet.
hifihvn
943 posts
 
Here is a YouTube video with a guy testing a couple of old tube amps. They're still going FWIW.[http://www.youtube.com/watch?v=jAjjc7ijGM4] [http://www.youtube.com/watch?v=Ayg6Y5CZgK0]
hifigeek1
770 posts
 
I watched the video and here is my interpretation of the performances. What he calls slant is actually called tilt or phase shift and it's measured in degrees. The Mac and the Dynaco look similar at maybe 20-25 degrees of tilt. This indicates that the low frequency response is rolled off. Possibly -3dB at 10-15 Hz. The Dynaco does a better job as the tilt is linear at low frequency. Therefore it's rolling off smoothly. The Mac on the other hand has tilt that is not linear at low frequency. At very low frequency the Mac frequency response might actually rise indicating some instability possibly caused by a coupling cap or power supply issue. High frequency response is similar on both amps with a bit of overshoot and only one or 2 cycles of well damped ringing. Some manufacturers do this so the amp sounds like it has greater high frequency response then it actually has. The Fisher looks like it has some major issues as it's high frequency response is not linear. It probably dips then rises and dips again. Either the amp has coupling cap issues, feedback cap issues, and/or the output coupling transformer is not properly compensated for. When the frequency response or any amp becomes non linear, i.e. rises and falls dramatically the test is pretty much over since that non linear response in not useable. I normally use sine waves to determine -3dB down points of an amp or preamp under test and confirm it with square waves.
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