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Capabilities of Realtek ALC655 sound on 7N400Pro2 motherboard



 
 
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  #1  
Old January 24th 04, 12:55 AM
Exp315
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Default Capabilities of Realtek ALC655 sound on 7N400Pro2 motherboard

Just passing on a few things I learned while trying to answer these
same questions for my own system:

1. What's the sound subsystem on the Gigabyte 7N400Pro2 motherboard?

It's the Realtek ALC655 chip, which supports the AC97 sound standard
with 6 channels and digital SPDIF input and output capability.
Realtek's site for information and up-to-date drivers:
http://www.realtek.com.tw/

Note that the 7N400Pro2 does NOT have the same capabilities as the
original 7N400Pro (these boards should really not have been labelled
so similarly). The original Pro had the more expensive nVidia MCP-T
chip with "SoundStorm" in addition to the Realtek codec (the MCP-T has
a DSP providing extra audio functions like real-time Dolby Digital
encoding).

2. Does the Realtek ALC655 on the 7N400Pro2 support 6-channel surround
sound?

Yes. It can generate 6 separate analog channels for full 5.1 surround
sound, just like a Sound Blaster Live card, for example. You can plug
it into an external 5.1 speaker system with a set of 3 analog audio
cables. If you have the audio extension bracket supplied with the
7N400Pro2, you will find the Rear L/R and Center/Sub channel
connectors on the bracket. Otherwise, you must change a driver setting
to switch the Microphone In and Line In jacks on the rear panel to
provide those extra connections. You must select 6-speaker
configuration on the sound control panel to activate all 6 channels.
You can test each channel individually from the control panel, and you
can use the HRTF demo function on the control panel to hear music
circle around the channels continuously.

If you don't have these functions on your control panel, download the
latest driver from Realtek.

3. Does it support digital audio input and output?

Yes. The 7N400Pro2 has SPDIF (Sony-Phillips Digital Interface) digital
audio input and output connectors on the motherboard, which are fully
supported by the Realtek chip. If you have the audio extension
bracket, you will find digital coax and digital optical (TOSLink)
output connectors on it, which are internally connected to the SPDIF
output on the motherboard.

4. Does anything have to be done to enable the digital output?

In WinXP, with the current Realtek driver installed, the digital
output seems to be always on. It continuously provides a two-channel
digital PCM data stream with the same sound you hear on the stereo or
front channels of the analog audio. It can be connected to external
digital audio devices like a digital speaker system using the coax or
optical connectors. Other users with different audio setups have
mentioned driver settings or WinXP settings which have to be changed
to enable digital output, but I have not found any applicable to the
this 7N400Pro2 setup, other than the SPDIF Mute checkbox on the Sound
Mixer control panel, which does affect it. You do not need to select
5.1 speaker mode or a room type on the sound control panel to activate
the digital output, and those settings don't affect the digital output
(only the 6-channel analog output).

5. Can this system produce Dolby Digital surround sound output?

Yes and no. If you are playing a sound source like a DVD which has a
pre-encoded Dolby Digital 5.1 sound track, and your player software
supports "pass through" mode (PowerDVD and NeroVision Express do),
then the driver will pass the encoded digital sound track through to
the SPDIF output without changing it. If you have an external Dolby
Digital decoder, it will get the full DD 5.1 surround sound signal. If
your player software does NOT support pass-through mode, then you will
get a "downmix" of only two channels supplied by the player software.

This sound system doesn't have the signal processing horsepower to
encode 6 analog channels to a compressed Dolby Digital 5.1 signal in
real time, unlike the SoundStorm version mentioned above. If your
source is not pre-encoded, you will get only two channels on the
digital output.

However some player programs and some games like Unreal Tournament
have the ability to produce Dolby Pro Logic surround sound encoding on
two channels in real time. If you have an external Dolby Pro Logic
decoder hooked up to the digital output, you will get a limited form
of surround sound from just the two source channels. This is not as
good as full Dolby Digital 5.1 surround sound though.

6. Can I control the level, balance, tone of the digital output?

With the current Realtek driver, no. These settings appear greyed out
on the mixer control panel. However if your player software supports
an equalizer function, you can control some items there. And you can
still control the WAV input level.

7. Does this system support EAX surround-sound effects for games?

Yes, the Realtek driver supports EAX (a Creative Labs standard
supported by many games), and will generate surround sound for games
that support it. This is done in software rather than hardware, so you
need a fast processor, and it will have a small impact on game
performance (about 5-10%). It's controlled by the game program
settings, so you don't have to do anything in the driver or control
panel to enable it.

8. Is the quality of the sound as good as a separate Sound Blaster
card?

That depends on your point of view. The built-in subsystem on the
motherboard sounds fine - there isn't any excessive noise or
distortion, and the frequency response is good. You don't get 24-bit
sound or 7.1 channel capability as you would with a high-end Sound
Blaster Audigy, but you probably wouldn't miss that for most PC sound
applications. You don't get the EAX extensions and hardware
performance boost that the Sound Blaster card has for game sound. You
don't get the CMSS capability to produce surround sound from stereo
sources. The Sound Blaster has more software accessories and better
support. But no version of the Sound Blaster can do real-time Dolby
Digital 5.1 encoding either.
  #2  
Old January 24th 04, 09:19 PM
John David Carter
external usenet poster
 
Posts: n/a
Default

Comparing most motherboard sound to an Audigy is kinda not relevant. The
ALC655 is basically Sound Blaster compatible, i.e. hardware acceleration
albeit minimal. So, it meets the minimum requirements for sound for gaming
which should be enough for most.

I have a K8VT800M Athlon 64 mobo with the ALC655, and while not as good as
the ALC658 it is more than okay. Of course, I prefer the SoundStorm that I
have in my NF7-S - which is hooked up to a DD home theater - but begars
can't be choosers.

Oh, and before I forget, my Stereo Home Theater A/V Receiver - which is in
the room with my Athlon 64 - has 5.1 inputs for previously decoded DD, so
basically I can hook my 5.1 from the ALC655 to it without needing the
hardware DD encoder of the SoundStorm. Most A/V Receivers of high quality
have this feature, and I mention it because you can usually get one cheap -
especially the old DD *ready* ones ( i.e. no built in decoding ) - cheap at
a pawn shop along with an old set of 5.1 speakers...



"Exp315" wrote in message
om...
Just passing on a few things I learned while trying to answer these
same questions for my own system:

1. What's the sound subsystem on the Gigabyte 7N400Pro2 motherboard?

It's the Realtek ALC655 chip, which supports the AC97 sound standard
with 6 channels and digital SPDIF input and output capability.
Realtek's site for information and up-to-date drivers:
http://www.realtek.com.tw/


- snip -

8. Is the quality of the sound as good as a separate Sound Blaster
card?

That depends on your point of view. The built-in subsystem on the
motherboard sounds fine - there isn't any excessive noise or
distortion, and the frequency response is good. You don't get 24-bit
sound or 7.1 channel capability as you would with a high-end Sound
Blaster Audigy, but you probably wouldn't miss that for most PC sound
applications. You don't get the EAX extensions and hardware
performance boost that the Sound Blaster card has for game sound. You
don't get the CMSS capability to produce surround sound from stereo
sources. The Sound Blaster has more software accessories and better
support. But no version of the Sound Blaster can do real-time Dolby
Digital 5.1 encoding either.



 




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