Ryan said:
I agree, I think the board is GREAT!, look for awhile for this. The
only issue that I'm having with it is the CMI9880. I think the software
they give blows. Enough of my rant and on to my particular issue.
I have the Logitec Z680 speakers and are being used via the on board
coax connection. Now when ever I play a MP3 or the "Windows Startup
Sound" plays there is a 1.5sec delay before the signal gets to my
speakers so I don't hear the beginning of the sound. I have never seen
the software display anything above 2CH with my 5.1 speakers. (This
could be because of the AC3 though??)
Also I was trying to get one of my MICs working today and found the
remapping feater of the ports on the back which is cool, although them
not working is not (as I can't use my MIC I get very little sound
through it). I just went through looking for updates on ASUS, CMEDIA
and via google turning up nothing.
Any have suggestion, pointer to more info, someone I can yell at.
Ryan
You know what that means. The AC3 encoder, that converts 5.1 sound
into the two digital channels in the SPDIF, takes a great deal of
processing power. Your measurement of 1.5 seconds of latency is
interesting, as that is the first time I've seen a number for
a software implementation. The A7N8X Nforce2 boards with MCP-T,
have a hardware DSP to do this function in the Southbridge.
With the digital section of the 9880 using only 14 milliamps, there
cannot be any DSP in there. The DDICE function must be using
your processor for conversion.
What should be interesting, with that DDICE function, is whether
in a multimedia situation, the DDICE encoding software is smart
enough to preserve synchronization between audio and video. It is
all right to have a 1.5 second delay, as long as the audio and the
video are delayed by the same amount. (Obviously, for the desktop
sounds, that stupid encoder should have a "fast path" for things
that only need two channels. I expect Dolby wrote this code and
not Cmedia, so don't expect something like that to change any
time soon.)
On an AC97 sound system, your mic problem would be fixable with
the "Mic Boost" button. AC97 adds 20dB gain to the microphone
via that control bit. The CMI9880 spec mentions "0 ~ 46.5dB with
1.5dB/Step" for the "Audio Input Widget", meaning the microphone.
With the volume slider all the way up, that should be enough for
a dynamic microphone (5mV signal would give full scale input).
If you are using an electret microphone, those use power from
the mic jack. The CMI9880 switches on the mic power, when you
declare a port as a microphone input. If you plug a male-male
1/8" stereo plug into the jack, then take a voltmeter and
measure from the middle contact to the ground contact (furthest
from tip of plug), you should see several volts DC on there.
That would indicate that the CMI9880 is trying to power the
microphone for you. If that power is missing, there shouldn't
be any microphone input signal to speak of. That power should
be current limited, and should be safe to short out.
/ \
-- mic ------| |
\ /
+===+
-- micpwr ---| | <-------
|===| |_____ Several volts DC when in
| | | microphone mode.
-- ground ---| | <-------
| |
+=======+
| |
Modern electret microphones can deal with pretty low voltages.
For best compatibility, the jack should really be providing
5V through a 2K resistor, to cover all possibilities. If the
CMI9880 only puts out 2V or so, then you may need a newer
electret microphone to get it to work. The analog power on
the CMI9880 is 5V, so it should be possible to do a decent
level on the mic power.
(Some typical electret microphones 1.5V, 2V, 4.5V)
http://dkc3.digikey.com/PDF/T043/1213.pdf
HTH,
Paul
