15 Apr
2008
15 Apr
'08
7:15 a.m.
On Mon, 2008-04-14 at 22:39 -0500, Tom Peters wrote:
You're recording the output of a 5150?? You mean
the original IBM PC? Have
we forgotten how the PC generated audio, until real audio cards were
generated? They just toggled a line connected to the speaker-- thereby
pumped square waves at it. Squarewaves are rich in harmonics, and sound
very harsh. They were reliant on the fixed response of the speak to smooth
it out mechanically. Recording that properly will be pretty hard. You need
an RC filter to try and smooth that out, and I'm not sure what that would
look like. Probably a capacitor from the hot lead to ground, with resistor
in the hot lead before the cap. It's still going to be harsh.
I don't know about harsh, but it won't sound like a PC speaker. If you
want it to sound exactly right you're going to have to mike it in a
quiet room.
It will be too "hot" certainly, and you will
have to pad it down with a
series resistor followed by one to ground. But as much of the distortion is
coming from trying to record squarewaves as from overdriving the recorder's
input stage.
You know that most synthesizers produce squarewaves, and they can be
recorded without any problems at all, right?
Jim: try this - 4.7k resistor onto the hot side of the speaker, 1k
resistor from the "free" end of the 4.7k resistor to ground, 1uF cap
from the junction of the two resistors to the line in
on your desk (and
obviously ground to ground on the desk). You may need to fiddle
with
the EQ to get a nice sound.
Gordon