Line In Imbalance
Line In Imbalance
- Subject: Line In Imbalance
- From: Chris Luth <email@hidden>
- Date: Fri, 01 Mar 2002 15:30:07 -0900
I think I posted something about this problem some time ago, but somebody
asked me if I could clarify the problem. Well, I9ve finally gotten around to
it, so here it is.
When I attempt to record an analog line in signal, adjusting the gain of any
recording program results in only changing the gain of the right channel.
Here's some info that might help clarify the problem, using Daisy, an
example source code given in Developer->Examples->CoreAudio->HAL->Daisy.
OS: 10.1.2
Computer: Apple PowerMac G4 350 PCI Graphics (Yikes! board)
_s represent unchecked boxes, Xs represent checked boxes. --^-- represents
the position of the fader.
For best results, the diagrams below should be in Courier New, 12 pt.
--Input Channel Volume & Mute-----------
ch mute scalar db playthru
0 ^----[Fader]------- _ 0.0 0.0 X
1 ^----[Fader]------- 1 _ 0.00 0.00 _
2 ^----[Fader]------- 1 _ 0.00 0.00 _
3 ^----[Fader]------- _ 0.0 0.0 _
4-8 similar to 3
--Input Channel Volume & Mute-----------
ch mute scalar db playthru
0 ^----[Fader]------- _ 0.0 0.0 X
1 -----[Fader]------^ 1 _ 1.00 22.50 _
2 -----[Fader]------^ 1 _ 1.00 22.50 _
3 ^----[Fader]------- _ 0.0 0.0 _
4-8 similar to 3
Only channels 1 and 2 have active faders (the rest are grayed out) and only
channel 0 had an active playthru checkbox.
When sliding the fader for input channel 1 up, the sound output goes up in
the right headphone, but not the left headphone. Bringing the channel 2
fader up also makes the sound louder in the right headphone and not the
left.
Here's what's interesting...if you bring the channel 1 fader all the way up,
and then you begin to move the channel 2 fader up from 0, the sound output
in the right channel is changed to reflect the position of the channel 2
fader...as if it is overriding the channel 1 fader (i.e. it gets soft, back
down to 0.00db, and then moves up to 22.50 as you move the channel 2 fader
up to the top).
So it's as if both channel 1 and 2 faders are only affecting the right
channel input. If you open an audio recording program and adjust the
recording gain from within the program with Daisy open in the background,
you'll see both channels 1 and 2 faders moving up as you increase the gain.
As you might suspect from the other info I've given you, it only affects the
right channel's input levels.
Right above the Input section is the Output section, and it's laid out
similarly. In fact, here's a typed-up version:
--Output Channel Volume & Mute-----------
ch mute scalar db
0 ^----[Fader]------- _ 0.0 0.0
1 -----[Fader]------^ 1 _ 1.00 0.00
2 -----[Fader]------^ 1 _ 1.00 0.00
3 ^----[Fader]------- _ 0.0 0.0
4-8 similar to 3
Funny thing is, adjusting the channel 1 fader affects the left channel, and
adjusting the channel 2 fader adjusts the right channel. Why is this not the
case with the input channels?
This problem affects my ability to record analog line in signals
effectively. Help and a solution would be nice. Just to note, this problem
does not occur when I reboot in OS 9.
Thanks,
Chris
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