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Topic: Sound card definitions (Read 5229 times) previous topic - next topic
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Sound card definitions

Hi all, i am a new comer to digital music.  I have been into traditional HiFi for many years.  But now wish to add digital music set-up to my system using my laptop.  How ever the world of sound cards is a complicated issue.  In trying to make a selection i need to know some to the terms and attributes that affect their performance.  I am only interested in sound quality.  My questions follow.

1) 16, 24 etc..  bit cards.  I think that may laptop has 16bit card which would explain the poor performance.  I think I need a 24bit external card.  I understand this is the sample rate but what can the human ear detect?  Isn’t CD hirer again?  Why aren’t there any hire bit cards on the market?

2) What is the bit rate (96kbs) how does this affect the sound quality?  What’s the best?

3) I’m planning to use digital optical out from the card (which ever one I chose) do either the sample rate or bit rate affect the digital output?

4) Are external sound cards which use the USB for power good?  Or would a separate power supply be cleaner and therefore better?

5) Because i will be using digital out will this by defection pass though the surround sound (I have a 6.1 system)?

6) How does the pc interface affect the sound quality (e.g. USB, USB2 or Fire wire)?

7) Finally has any one used the M-Audio Transit?  Is it as good as the Audiophile USB for digital out?

Thanks

Sound card definitions

Reply #1 –
1) 16,24 etc... is the bit depth of the card. It determines how loud the digital noice introduced by the card will be. An ordinary CD uses 16 bits. 24 is better but normally not needed for regular playback.

2) A soundcard does not have a bitrate. I guess the number you are refering to is the sample rate (samples/second). This determines the highest frequence that can be reproduced. A normal CD uses 44.1 KHz, which makes it possible to reproduce frequences of up to 22 KHz (sample rate / 2).

Sound card definitions

Reply #2 –
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1) 16, 24 etc..  bit cards.  I think that may laptop has 16bit card which would explain the poor performance.  I think I need a 24bit external card.

16-bit is not necessarily "poor". CD audio is also 16-bit. There are of course several poor 16-bit sound cards in existence (but that's mostly because of their price range). One advantage you have with choosing a 24-bit card is of course the fact that 24-bit cards usually have good audio quality (i.e. the chance that you would accidently pick a bad 24-bit sound card is small).

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I understand this is the sample rate but what can the human ear detect?  Isn’t CD hirer again?  Why aren’t there any hire bit cards on the market?

This is not the sample rate, but the bit-depth. The sample rate indicates the number of samples per second. For example, audio CD uses 44100 Hz (44.1 kHz), DAT uses 48000 Hz (48 kHz).

About the bitdepth: As I mentioned before, CD audio uses 16 bits. With 24 bits, you will get more precision per sample, and subsequently a higher dynamic range.

I personally believe 16-bit is "good enough", i.e. it's probably at the limit of human hearing capabilities. I don't think there has been any definite proof that humans can hear the difference between 16-bit audio nd 24-bit audio. However, the extra precision of 24-bit is welcome when you use additional processing of the sound (effects/DSP), because this processing can introduce rounding errors.

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2) What is the bit rate (96kbs) how does this affect the sound quality?  What’s the best?

The bitrate indicates the number of bits the audio uses per second. Since CD audio uses 44100 Hz, 16-bit audio it uses 1411200 bits (1411.2 kbps) per second.
Calculation: 44100 samples per second x 16 bits per sample x 2 channels (stereo) = 1411200.

As you can see, 1411.2 kbps is quite a bit higher than the 96 kbps you mentioned. This is because lossy codecs like MP3 can compress the audio to a fraction of the original size (mostly because it tries to remove as much audio data as possible while still trying to sound as close to the original as possible).

Higher bitrates result in higher audio quality (because the file is closer to the original), but also in bigger files.

To give you any idea: most modern codecs sound transparent (indistinguishable from the original) around 160kbps. Note that this is just a very rough estimate, please don't take it as an absolute truth!

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3) I’m planning to use digital optical out from the card (which ever one I chose) do either the sample rate or bit rate affect the digital output?

Sample rate and bit rate always affects the overall quality (see previous points), whether you use analog or digital outputs.

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4) Are external sound cards which use the USB for power good?  Or would a separate power supply be cleaner and therefore better?

In theory, a separate power supply could be cleaner, but I think the USB power from most systems would be adequate.

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5) Because i will be using digital out will this by defection pass though the surround sound (I have a 6.1 system)?

Are you sure it's 6.1 and not 5.1? Anyway, on most systems the surround sound should pass through just fine, but I don't have any personal experience with it.

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6) How does the pc interface affect the sound quality (e.g. USB, USB2 or Fire wire)?

If you use an external interface like USB or Firewire, you eliminate the risk of getting interference from other components inside your PC case (like you can get with internal sound cards). So this is an advantage of an external interface. Using USB2 or Firewire shouldn't make any difference in sound quality at all.

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7) Finally has any one used the M-Audio Transit?  Is it as good as the Audiophile USB for digital out?

If I had to buy a USB sound card right now, it would be the Transit. I haven't used the card myself, but it seems to be a nice card.

Phew. That was quite a bit to type (and I've still only scraped the surface of digital audio).

I hope it's useful to you.
Over thinking, over analyzing separates the body from the mind.

Sound card definitions

Reply #3 –
One more thing: since you appear to be looking for sound card to use in your laptop, you could also consider the Echo Indigo range of PCMCIA sound cards:
http://www.echoaudio.com/Products/Indigo/

The sound quality should be excellent (read some reviews), and it's a bit more convenient to use than an external USB or Firewire card (with the cable).

Edit: Argh, I forgot that these cards only have analog outputs. So if you need digital outputs these cards are not for you, sorry.
Over thinking, over analyzing separates the body from the mind.

Sound card definitions

Reply #4 –
Thanks very much for you information, it makes things clearer.

Another issue that i was wondering about was the diffrence between SP-DIF and optical output.  My amp has both so i could use either.  As things are digital does this meen that there is no real issue unless the cables length is realy long?  I was only planing on using 5 meters.

Sound card definitions

Reply #5 –
i would chose a soundcard that doesn't do any kind of resampling or other processing to the signal. then if your amp (probably a surround (pre)amp) has spdif input connect the spdif of the soundcard to your amp. many soundcards support ac3 or dts sendthru via spdif. this means you can playback a multichannel dvd for example and listen to it in 5.1 (or whatever) on your hifi system. also spdif supports longer cable lengths and is much cheaper than optical cables as far as i know.

maybe you will find something nice here: http://www.m-audio.net

edit: optical seems to support dts and ac3 senthru too. sorry about that.

Sound card definitions

Reply #7 –
À propos S/P-DIF... Does anyone know a S/P-DIF to TOSLINK converter which doesn't alter the sound very much? I would like to digitally transfer some files from my computer to the MiniDisc without having to burn a CD and use it in my HiFi system.

Sound card definitions

Reply #8 –
Optical is always SPDIF (exept professional 8-tracks optical).

Your receiver certainly accept SPDIF digital signals. Consumer soundcards have SPDIF digital output. Professional soundcards can have either SPDIF, either AES/EBU digital outputs, either both.

SPDIF usually exists in optical or electrical.
When it is optical, it is TOS-Link plugs.
When it is electrical, it is CINCH coaxial plugs (also called RCA), exept on some soundcard, that can output electrical SPDIF into a mini jack, or some esoteric CD Players, that can output electrical SPDIF into BNC plugs.

You can't mistake AES/EBU, as it always use XLR plugs.

The usual consumer choice for SPDIF : optical (Toslink) or coaxial (RCA) ?
The advantages of coaxial are the price, and the possible lenght.
The advantage of optical is the absence of electrical interference causing drop outs, that can occur when a computer feeds a receiver, when you switch a light.
Optical is OK for 5 meters.

Coaxial to optical (and conversely) converters are expensive. About 80 € for the Fostex COP 1, for example.

Sound card definitions

Reply #9 –
Important disadvantage of electrical digital cables:

If the computer and a HIFI component are connected, there can appear a strange behaviour called (German) "Brummschleife". I don't know the English word and it's not in the dictionary, I try to translate: drone-loop

This appears if too many mass connections are made, a loud drone can be heard from the HIFI receiver. The current circuit leads from the power supply system's ground to the computer's case, the receiver's case and through the receiver's (cable)  antenna back to ground.
Optical cables avoid this, because they interrupt the mass connection.
I know that I know nothing. But how can I then know that ?

Sound card definitions

Reply #10 –
precisionist,

I'm guessing what you're describing is what we call a ground loop or earth loop or simply "hum"!

It's usually solved (or reduced) by disconnecting the earth/shield at one end on the audio cable itself.

Of course you're right: optical cables don't have this problem!

Cheers,
David.

Sound card definitions

Reply #11 –
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Does anyone know a S/P-DIF to TOSLINK converter which doesn't alter the sound very much? I would like to digitally transfer some files from my computer to the MiniDisc without having to burn a CD and use it in my HiFi system.

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Coaxial to optical (and conversely) converters are expensive. About 80 € for the Fostex COP 1, for example.

You could uild one yourself fairly cheaply. The modules are made by Toshiba and are part TO[R/T]X172 (IIRC, a search of diyaudio.com will point you in the right direction). If you get a good deal on the optical unit,the rest shouldn't cost in excess of USD5 to build.
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It's usually solved (or reduced) by disconnecting the earth/shield at one end on the audio cable itself.

That does work, but can introduce other problems. There are better ways to remove ground loops and grounding related hum.
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4) Are external sound cards which use the USB for power good? Or would a separate power supply be cleaner and therefore better?

This is a difficult one, and depends on what you are expecting. For example, Texas Instrument's popular PCM270* line of USB DAC ICs offer about half the THD+N (Total Harmonic Distortion+Noise) when self powered than when powering off the bus (0.006% and 0.012% for the PCM2704). Unless the chip is very badly implemented the THD figure will be acceptable when powered from the bus. This isn't a major point when choosing a card.
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6) How does the pc interface affect the sound quality (e.g. USB, USB2 or Fire wire)?

All USB (and USB2) cards I have seen measured have about a -65dB 1kHz hum picked up from the bus (including one I designed and built myself). I haven't seen any good measurements of a firewire card.
Also, the data rate on the USB Bus will limit you to 2 24bit 96kHz channels, so no high-rate 5.1 for you. If you don't card about high rate (over 48kHz) or surround (seems like you do) then USB1 is fine.

Sound card definitions

Reply #12 –
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If you get a good deal on the optical unit,the rest shouldn't cost in excess of USD5 to build.

Really ? Don't forget the power supply for the optical devices. I don't know if one is needed for optical to coaxial, but you need it for coax to optical.

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It's usually solved (or reduced) by disconnecting the earth/shield at one end on the audio cable itself.

I've seen this done with twinax cables. The earth is connected with the second wire inside the shield. It's the first time I see mentionned no ground connection at all for a coaxial cable.

Sound card definitions

Reply #13 –
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If you get a good deal on the optical unit,the rest shouldn't cost in excess of USD5 to build.

Really ? Don't forget the power supply for the optical devices. I don't know if one is needed for optical to coaxial, but you need it for coax to optical.

If the device is used together with a soundcard, you can simply use the computer power. I have built one myself and used 5V from the computer to power it.  It works ok...
I use it for connecting the coax digital out on my M-Audio Audiophile to the optical in on an old portable MD-player.

Sound card definitions

Reply #14 –
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Really ? Don't forget the power supply for the optical devices. I don't know if one is needed for optical to coaxial, but you need it for coax to optical.

Unless you are really committed, a standard 3 leg 5 volt regulator and a 9V wall wart are all that is needed. Or you could steal power from the computer's PSU (i would reccommend taking +12v and regulating down to 5v).

Sound card definitions

Reply #15 –
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To give you any idea: most modern codecs sound transparent (indistinguishable from the original) around 160kbps. Note that this is just a very rough estimate, please don't take it as an absolute truth!

That is pretty rough! Try an extra zero . Actually 320kbs is quite good.

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4) Are external sound cards which use the USB for power good?  Or would a separate power supply be cleaner and therefore better?

In theory, a separate power supply could be cleaner, but I think the USB power from most systems would be adequate.

Yes, and with the optical ouput I'm sure it would make no difference at all.

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7) Finally has any one used the M-Audio Transit?  Is it as good as the Audiophile USB for digital out?

If I had to buy a USB sound card right now, it would be the Transit. I haven't used the card myself, but it seems to be a nice card.

I have it, and it's a nice card, although my DAC is on its way so I've only tried the analog out and in.

Sound card definitions

Reply #16 –
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That is pretty rough! Try an extra zero . Actually 320kbs is quite good.

I would recommend that you read the FAQ and the articles linked there. ~190kBit VBR is transparent on the vast majority of samples (with the proper encoder).
You can find it here:
http://www.hydrogenaudio.org/forums/index....t=ST&f=5&t=7516
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Yes, and with the optical ouput I'm sure it would make no difference at all.

Certainly. There is a question of jitter and various other arguments, but unless your power is VERY dirty a digital stream (especially optical) will be perfect.

Sound card definitions

Reply #17 –
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That is pretty rough! Try an extra zero . Actually 320kbs is quite good.

I would recommend that you read the FAQ and the articles linked there. ~190kBit VBR is transparent on the vast majority of samples (with the proper encoder).

Hmm. That does surprise me; perhaps the software has advanced a lot. I just tried 192kbs on a recording of mine and I was quite impressed with it. The recording was solo violin with very cheap equipment (<$200 in all, with minidisc compression in between) and the mp3 and wav compared with unamplified headphones. In a brief test I didn't notice the difference. When my new recording equipment comes in and my hi-fi system is complete I'll test properly.

Sound card definitions

Reply #18 –
Ive got my sound card which is a m-audio sonica theater, im trying to use the spdif out to play back my mp3 and wma's.  The spdif is connected to my av amp.  I can get WINDVD4 to play back using this conection by windows media player 9 will not.  It reports an error message "your sound card may not be working correctley".    Is there a patch/option to get it to work?  Please help?