BEC Posted November 22, 2006 Share Posted November 22, 2006 I recently bought one of these Edirol (Roland) 2 channel portable digital recorders. Since it can record directly as a 44.1 or 48 kbps WAV or about any bitrate of MP-3, thought I might be able to do some comparisons. Bob Crites Quote Link to comment Share on other sites More sharing options...
BEC Posted November 22, 2006 Author Share Posted November 22, 2006 Ok, here is the idea. First I will run the output of my HP sweep generator directly into the Wavtek spectrum analyzer to see how that looks. Sweep was from 20 to 22Khz. Next, record that same signal out of the sweep generator as a: 48 Khz (24 bit) WAV 320 kbps MP3 224 Kbps MP3 192 Kbps MP3 160 Kbps MP3 128 Kbps MP3 96 Kbps MP3 And play them back into the spectrum analyzer. Then off-set each a couple of db so they can go on the same sheet as a trace from the spectrum analyzer. Notice that this is all done wired. No mics or actual audio are involved, so this test should should show the maximum capability. Bob Crites Quote Link to comment Share on other sites More sharing options...
BEC Posted November 22, 2006 Author Share Posted November 22, 2006 Now the trace with all those on the same sheet. Bob Crites Quote Link to comment Share on other sites More sharing options...
BEC Posted November 22, 2006 Author Share Posted November 22, 2006 Now for what I think about this. We can see the first trace as the best we could get since it does not even involve a recorder. The second trace is very good also with only a small roll-off at the very top. Perhaps 3 db lost in the record/playback only above 20 khz. The first MP3 (320 Kbps) drops us back to about 16 khz. Seems that this must be set by the recorder to be the top since it does not roll off, just drops. Seems I can see no difference at all between the 224, 192, and 128 Kbps MP3. The all drop off exactly together at a bit below 16 Khz. The 96 Kbps MP3 takes a big hit with a drop off at around 11 Khz. Bob Crites Quote Link to comment Share on other sites More sharing options...
Champagne taste beer budget Posted November 22, 2006 Share Posted November 22, 2006 Very interesting, Bob. Thanks for taking the time to do the tests. Nice graph, too. Quote Link to comment Share on other sites More sharing options...
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