For audio band distortions you just need what is called Wave Analyzer (in
other
words spectrum analyzer) in 5Hz -50kHz. I own one with some same spare - HP
analyzer for audio band.
Any scope is not capable to "see" small distortions....
Greg
At 04:14 PM 2/7/07 -0500, Kuba Ober wrote:
I was talking about "aligning" audio circuits, e.g. adjusting operating
points of various stages, checking response, etc. Not about any sort of
RF work.
If I wanted to see a nonlinearity of a stage in an audio power amp, for
example, it'd be nice to believe that the scope's vertical system is
linear enough, etc. Same goes for step response: hard to do with a scope
that may well distort even a perfect square wave.
Anyone who is at all capable of making those kind of measurements
would surely measure the input square wave first. If it looks like
a square wave, then the scope is good enough for the task.
The input will look like a square wave even with a badly nonlinear vertical
channel. The output "square" wave will then typically be much slower than
the
input one you fed to your system. With nonlinear vertical, the slower
transitions on the output square wave will look distorted, and you may
end up
chasing ghosts, especially if the audio amp alignment procedure mentions
e.g. "adjust Rxxx for output transitions to be smooth".
I just don't believe in using unchecked instruments, and a reasonable way
to
check a 7603 with plugins is to use the classic calibration trio in a
TM503,
plus a mainframe standardizer.
How on earth can anyone recommend using an unchecked, unknown scope to a
newb
is beyond me. Newbs tend to misunderstand limitations of instruments they
use, so they are very likely to just blindly trust the trace, even if
someone
experienced would check things twice first. You know, things like using too
much or too little of vertical deflection, not centering the signal and
hunting differing rising/falling edge aberrations, and so on. It's just
very
easy to hit those on an uncalibrated scope methinks.
Cheers, Kuba
Emacs!
