Posted by manualblock [ 24.191.167.32 ] on October 07, 2004 at 15:15:27:
Menno wrote an article on testing OPT's in the Issue 5 1997 Glass Audio. In the article he goes over some methodologies for determining the specs of OPT's and how they affect sound. Some interesting conclusions are demonstrated at the end of the article. One of the points he makes is this:
Through extensive testing three postulates are promoted:
Human hearing reacts to pleasureable sounds by producing alpha brain wave activity measured at the 8hz level determined by EEG measurements. Testing has shown an increase in these EEG readings in subjects exposed to Tube amps with damping factors around 4, no negative feedback and rolled off high end starting at 16k.
In amplifiers that measured significant response energy at the 22k level, the positive alpha waves decreased significantly and the sound registered as unpleasant.
Using recordingds made with a double sampling speed DAT.recorded at 48k on speakers with tweeters able to reproduce frequencies in excess of 28k the pleasurable alpha waves and positive response returned to previously high levels.
It is a long article but very interesting. J.R.
In that same issue our own Metasonix has a nice article on modifying an 811 amp to make it sound better.
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