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Stereo System + AV Amp 5.1 channels
GreatKent
post Nov 3 2008, 14:02
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I have two soundcards on my HTPC. Also I have a decent stereo system plus a general AV 5.1 channel system. When watching multichannel audio movies, have you ever thought of using the decent stereo for front channels and the AV amp for the Rear Left , Rear right and subwoofer? I have the following setup to realize it:
Decode the audio using AC3Filter, spread the centre channel to the two front channels, pass it the stereo using digital PCM
pass the rest channels to AV am using analogue 5.1 input.

Now I have a question: Is it possible to output to both amps using digital cable? i.e: spdif passthrough to av amp and digital pcm to stereo, using two soundcards?
Thanks a lot in advance! biggrin.gif smile.gif biggrin.gif
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Slipstreem
post Nov 3 2008, 14:22
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Not a direct answer to your question, but...

But how do you quantify "decent"? Can you really tell the difference in audio quality between your normal stereo amplifier and the AV amplifier running in conventional stereo?

I had the same kind of dilemma myself when first setting up my surround system via optical digital. My previous setup had been an analogue link to a very high quality homemade stereo amplifier. The homemade amplifier beats the JVC AV amplifier in almost all respects on paper by a large margin, but I couldn't hear any difference in reality.

Are you sure you can? You could save yourself a lot of messing around if you can establish this as fact first. smile.gif

Cheers, Slipstreem. cool.gif
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GreatKent
post Nov 3 2008, 17:41
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QUOTE (Slipstreem @ Nov 3 2008, 07:22) *
Not a direct answer to your question, but...

But how do you quantify "decent"? Can you really tell the difference in audio quality between your normal stereo amplifier and the AV amplifier running in conventional stereo?

I had the same kind of dilemma myself when first setting up my surround system via optical digital. My previous setup had been an analogue link to a very high quality homemade stereo amplifier. The homemade amplifier beats the JVC AV amplifier in almost all respects on paper by a large margin, but I couldn't hear any difference in reality.

Are you sure you can? You could save yourself a lot of messing around if you can establish this as fact first. smile.gif

Cheers, Slipstreem. cool.gif


Hi Slipstreem, nice to hear from you~

Answer to your question is Yes! I can hear the difference! My stereo system produces much clearer sound, full range frequency much more balanced. The sound is very pleasant and clear even I turn the volume to 6 o'clock, which the sound level is same as or even higher than it is in cinema.
The Stereo not only beats AV amp on paper, but also on price! It's > 600% more expensive than te AV amp!
Just wonder if you already noted the followings when playing music on HTPC:

1.) Use lossless audio format, i.e: WAVE, FLAC, APE
2.) Use ASIO driver to get around Window's internal messy mixer
3.) Use decent sound card which doesn't resample internally! Creative SoundBlaster is well known crab in this way, it always resample!


Cheers,
GreatKent
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Slipstreem
post Nov 3 2008, 18:06
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QUOTE (GreatKent @ Nov 3 2008, 16:41) *
Just wonder if you already noted the followings when playing music on HTPC:

1.) Use lossless audio format, i.e: WAVE, FLAC, APE
Yes. And I hear no difference personally between lossless and a LAME MP3 VBR encoding at -V3 (~175Kbps).
QUOTE
2.) Use ASIO driver to get around Window's internal messy mixer
I'm using a third-party bit-perfect driver and always keep any player software volume controls set to 100% so, AFAIK, I'm hearing a bit-perfect source (or near as damn it) already.
QUOTE
3.) Use decent sound card which doesn't resample internally! Creative SoundBlaster is well known crab in this way, it always resample!
I haven't bought a Soundblaster since the original AWE32. Everything since has been based on independent reviews and technical specs rather than brand name. My current 14UK Trust 5.1 SC-5250/514DX soundcard (laugh if you like wink.gif) is free from resampling problems to the best of my knowledge.

I bought it for its optical digital output primarily, but the analogue side is more than adequate for me via a pair of Sennheiser HD447 headphones. smile.gif

Cheers, Slipstreem. cool.gif
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GreatKent
post Nov 3 2008, 18:31
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QUOTE (Slipstreem @ Nov 3 2008, 11:06) *
QUOTE (GreatKent @ Nov 3 2008, 16:41) *
Just wonder if you already noted the followings when playing music on HTPC:

1.) Use lossless audio format, i.e: WAVE, FLAC, APE
Yes. And I hear no difference personally between lossless and a LAME MP3 VBR encoding at -V3 (~175Kbps).
QUOTE
2.) Use ASIO driver to get around Window's internal messy mixer
I'm using a third-party bit-perfect driver and always keep any player software volume controls set to 100% so, AFAIK, I'm hearing a bit-perfect source (or near as damn it) already.
QUOTE
3.) Use decent sound card which doesn't resample internally! Creative SoundBlaster is well known crab in this way, it always resample!
I haven't bought a Soundblaster since the original AWE32. Everything since has been based on independent reviews and technical specs rather than brand name. My current 14UK Trust 5.1 SC-5250/514DX soundcard (laugh if you like wink.gif) is free from resampling problems to the best of my knowledge.

I bought it for its optical digital output primarily, but the analogue side is more than adequate for me via a pair of Sennheiser HD447 headphones. smile.gif

Cheers, Slipstreem. cool.gif


Nice! You are already an expert! cool.gif
Personally i also hear no difference between lossless APE and MP3 at 320kpbs CBR. I have tested few times with Eagles Hotel California. One is APE, the other is MP3 compressed from that APE file. I have tried both output via sound card and DAC USB. Also I have comparied the 25UK SPDIF coaxial cable and my hand made inexpensive coaxial calbe. I cound not tell the difference at all. I really wonders why. where is the damn problem? Is it really because HTPC not being a good source compared to traditional damn expensive CD player? But, as an electronic engineering graduate, i really cannot believe CD player is better than PC! I wonder if someone has more insight in it. rolleyes.gif
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Slipstreem
post Nov 3 2008, 19:05
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If you're using a S/PDIF connection (either optical or coaxial) with a bit-perfect soundcard driver already then, assuming that your encodings are lossless and error-free, the signal exiting the PC is going to be better than that leaving the analogue or digital outputs of almost any standalone CD player. The only limiting factor apart from the analogue stages of the main amplifier itself is the quality of the DAC employed to translate the signal from the digital domain to the analogue domain.

The reason you hear no difference between any lossless format and MP3 at 320Kbps is that, to all intents and purposes and according to the human ear, there usually are no differences except in the case of rare audio signals that may trip up the encoder. The psychoacoustic modelling of lossy encoders is designed to do just that and succeeds the vast majority of the time given sufficient bitrate to play with.

If you're making your own MP3 encodings from lossless sources, I'd highly recommend that you experiment with ABX (blind test) comparisons between lossless source material and various levels of VBR MP3 compression. It's highly likely that you don't need a constant 320Kbps to achieve perceptual transparency. The vast majority of people don't.

Apologies for still not having answered your original question, but I think it's important for you to determine your own personal requirements in terms of actual quality before assuming that it's much higher than it may be in reality. It gives a person a realistic reference point rather than automatically assuming that the most expensive approach (either in terms of bitrate/storage space or money) is always the best to take. smile.gif

Cheers, Slipstreem. cool.gif

This post has been edited by Slipstreem: Nov 3 2008, 19:15
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DVDdoug
post Nov 13 2008, 00:27
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I'm not 100% sure about this, but I think you can only send the sound (from one application) to one soundcard at a time. Have you confirmed that you can get sound from both soundcards at the same time?

This sounds like a really convoluted "solution", and in the process you are loosing your center channel.

But, if that's what you want to do, a more straightforward way to downmix the 3 front channels would be with an analog mixer. You just need a stereo (stereo output) mixer with at least 3 input channels, and pan controls on each channel. (I think you could find a little mixer like that for around $100 USD.)


QUOTE
But, as an electronic engineering graduate, i really cannot believe CD player is better than PC! I wonder if someone has more insight in it.
You might get more noise from some soundcards (analog outputs), and I've looked at the analog output from my (cheap) soundcards/soundchips on my computers at work with an oscilloscope. There is absolutely no filtering! I can get a "nice" 24kHz square wave! (At a 48kHz sample rate.) Even more interesting, when I try to send out a 20kHz signal, I don't get a 20kHz square wave... I see a sequence of 24kHz (2 samples) and 16kHz (3 samples) pulses! (I assume the average frequency is 20kHz, but that's not so easy to measure with the equipment I have.) NOTE - I'm not saying I can hear the defects (or ultrasonic harmonics wink.gif ), but the results were interesting. (I have not done any tests with my CD player or home computers yet.)
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GreatKent
post Nov 19 2008, 17:41
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QUOTE (DVDdoug @ Nov 12 2008, 17:27) *
QUOTE

I'm not 100% sure about this, but I think you can only send the sound (from one application) to one soundcard at a time. Have you confirmed that you can get sound from both soundcards at the same time?

This sounds like a really convoluted "solution", and in the process you are loosing your center channel.

But, if that's what you want to do, a more straightforward way to downmix the 3 front channels would be with an analog mixer. You just need a stereo (stereo output) mixer with at least 3 input channels, and pan controls on each channel. (I think you could find a little mixer like that for around $100 USD.)


You are right! I spread the central channel over 2 front channels. Yet instead of external mixer, I use software for the mixing. It's also normalized and sent out through SPDIF. But the other 3 channels (2 surrounds and 1 LFE) are converted into analog signal by soundcard. The result is quite good. I just wonder if it can be further improved by sending raw DD or DTS signal through 2nd soundcard. Then I can use the AV amp internal DAC to reduce noises induced by analog signal tranmission.

QUOTE
But, as an electronic engineering graduate, i really cannot believe CD player is better than PC! I wonder if someone has more insight in it.
You might get more noise from some soundcards (analog outputs), and I've looked at the analog output from my (cheap) soundcards/soundchips on my computers at work with an oscilloscope. There is absolutely no filtering! I can get a "nice" 24kHz square wave! (At a 48kHz sample rate.) Even more interesting, when I try to send out a 20kHz signal, I don't get a 20kHz square wave... I see a sequence of 24kHz (2 samples) and 16kHz (3 samples) pulses! (I assume the average frequency is 20kHz, but that's not so easy to measure with the equipment I have.) NOTE - I'm not saying I can hear the defects (or ultrasonic harmonics wink.gif ), but the results were interesting. (I have not done any tests with my CD player or home computers yet.)



Hi DVDdoug, it's nice to shar your experience!
I remember at university I have also checked digital signal on CRO, the digital signal was noisy and not at all square wave! From what i learnt from signal course, digital system use edge detection instead of level detection. It can send 1 & 0 as long as the rising or falling edge can be dectected. It's much more noise-resistant than level detection.

This post has been edited by GreatKent: Nov 19 2008, 17:53
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