The Best Audio Interface

Introduction

Have you ever been at the point that you are wondering if you use the correct audio link between your PC and your audio set or speakers? Have you ever been at the point that you replaced your analogue connections by a toslink cable and find out that most of the time you have stereo sound in stead of surround? I've been there and took the time to find out what the cause is. Each application has other demands and preferences, and thus a different approach for finding the best connection. On this page I've described the basics and used drawings in order to make it clear. I hope it helps you and saves you time.

Abbreviations & definitions used in this article;

HT = Home Theatre.

PC = Personal Computer.

OS = Operating System (Windows, iOS, Linux, etc).

Toslink = an optical cable often used for transferring a digital audio signal.

SPDIF = same digital audio signal as Toslink, only with electronic signals in stead of optical.

Disturbance and Analogue vs Digital

There are many possible causes of noise on analogue signals. Digital signals can also be disturbed, but they are much less sensitive, especially if they are differential. I'm not going to describe all types of signal disturbance, nor explain the difference between analogue and digital signals. It is common knowledge that the data transferred with digital signals is much less likely to be disturbed than the same data transferred as analogue signals (excluding signal modulation techniques). If you don't want to accept that, this page is not for you. In addition, I assume the common assumption that the longer the analogue cables between PC and amplifier, the higher the chance there are added signals (unwanted sounds) and/or quality loss.

Effect of cabling

I hope I do not have to convince you that a more expensive cable does not solve all problems. Of course, there are unwanted effects that can be eliminated by buying a better cable, but they certainly aren't the 'holy grail'. Just make sure your cable is decent; all connections should be reliable and cables should be thick enough to transport the power (current) you send to your speakers.

My personal experience

This chapter contains a story about my personal history with audio connections and why I wrote this article. You can safely skip it as it is only as correct as my memory is, besides it may not even help you.

Phase 1

Like most of the people that use a PC, I had an analogue stereo connection to an external amplifier with 2 speakers. For most people this would be a desktop stereo-speakerset with internal amplifier, I used an external cheap all-in-one hifi-set. I think I used a simple sound-card as on-board sound was not widely available.

Phase 2

As I was getting more and more involved in gaming, and started getting some money due to small jobs. I decided to upgrade my sound experience. I spend about fl 800,- (pre-euro money named 'guldens') which was a lot for that time, especially for a student. The new goods were a Sound Blaster Live 5.1 and a Cambridge DTT2500 surround speaker set. The investment was totally worth it as it gave me surround sound of a quality I never had before.

Phase 3

Sometime on-board sound cards became mainstream. I remember I tried it but wasn't happy with the result. I do not remember if it was due to audio quality or malfunctioning surround. Anyway, I preferred the Sound Blaster Live and kept using it.

Phase 4

I think it was the moment that I switched to Windows XP (or was it Longhorn?) that driver support for the Sound Blaster Live was terrible. I couldn't get it to work anymore and was forced to use on-board audio for some time. I thought I was doing good by using SPDIF, in addition I only had to connect a single cable. At first I didn't mind it a lot but after a time I realised that often there was no surround sound, only stereo. I tried to fix it, but it wouldn't work as I expected and gave up on surround sound for gaming.

Phase 5

What I do remember, was that NVidia marketed a motherboard with on-board audio, called 'Soundstorm'. Yes, NVidia was in motherboard development back then, and they were good at it! The sound that Soundstorm brought to my DTT2500 was amazing! I was very happy with it for a very long time and used the motherboard as long as I could.

Phase 6

The moment that I had to say goodbye to Soundstorm had come with the next motherboard. I went back to 'normal' on-board audio which I connected only with SPDIF as it worked before. Alas, the 'sometimes surround, sometimes stereo' situation was back. I hated my new motherboard for its on-board audio, and the Sound Blaster Live wouldn't work. During this phase I started my research and found that surround would work if I used the analogue connections. I never understood why, but it was a working solution.

Phase 7

In many years following I kept using the DTT2500 speakerset with different on-board sound cards. Some times I tried using only the SPDIF but it never worked properly. For a reason I can't remember there was a moment were I decided to stop with the analogue connection and only use SPDIF, I accepted the fact that games were in stereo and not in surround.

Phase 8

When I bought a receiver for my home cinema set, I wanted to try it ASAP. I had read that I could connect it via HDMI and as a test I connected it with my PC. This opened my eyes in many ways; not only were all receiver properties (supported bitrates and codecs) automatically detected, in addition it gave me way better audio quality and surround that always works. Simple as plugging in the HDMI connection. I browsed online for a cause / explanation what I experienced. And all the reason for my frustrations in the past became clear; SPDIF/Toslink is not what I thought it was. My findings and new knowledge are listed in the next chapters.

The analogue audio connections

It is very common to use an analogue audio signal from your PC to your PC speakers. Each channel (2 for stereo, 6 for 5.1 surround) has its own cable to transfer the 2 poles needed to create a sound. While headphone speakers do not require an additional amplifier, desktop speakers commonly have one. This amplifier amplifies the analogue signals, including all disturbances, to a power level that is sufficient to drive your speakers. Bigger speakers and/or a higher volume normally need more amplification. See the schematic drawing below for more info.

Description of drawing:

In the PC (or other source that handles digital audio formats) the digital audio is decompressed and sent to the mixer built in your OS. The mixer can handle several audio sources at the same time, like playing mp3 music on the background while playing a game. The mixer sends the resulting audio to the sound card in your computer. At the present time it is common to use your onboard sound card, but it may be an extension card plugged in the mainboard. The sound card converts the data send by the mixer to analogue signals and puts them on a connector to the back of your PC. From there you connect them to the external amplifier and the external amplifier amplifies the signal for driving your speakers.

This method has as main disadvantage that there is a long path with the analogue signals. All disturbances added to the analogue signals before the amplification, are amplified as well. This creates noise which may be audible or even annoying. In addition the analogue signal cannot be easily isolated electrically, and therefore it may happen that a 50Hz signal is added due to different power nets.

Toslink, an improvement?

Since transferring audio signals digitally is less sensitive for disturbances, why doesn't everybody use Toslink or SPDIF? The main advantage of Toslink over SPDIF is that Toslink is optical and therefor makes no electrical connection between your source (PC or HT) and your amplifier, this excludes to possibility for 50Hz humming. For the rest of this page I consider Toslink and SPDIF to be the same, and refer to them both when using 'Toslink'.

Toslink isn't what you expect it to be. Yes it is a digital audio interface and therefore eliminates many possible causes for disturbances. The problem is that the bandwidth is very limited. Due to this limit it can either transfer up to 6 encoded audio signals (like DTS or DD) or 2 raw signals (PCM). This results in the following schematic structure.

Description of drawing:

So, what happens if you only connect a Toslink cable (and have correct settings) is that the source has to be encoded in order to get surround sound. If your sound card does not support the live encoding of surround sound, the stereo channels are send over Toslink as PCM signals. If your sound card does support surround encoding, the full 5.1 channels are transferred over the Toslink cable.

"Why do I sometimes have stereo and other times have surround sound?" you may be wondering. This is because some sources, like movies and series, have encoded surround sound in their source file. If this surround sound is decoded to be mixed by your OS audio mixer, it again depends on your sound card if you will have surround sound from your speakers. Therefore the mode 'passthrough' is preferred. By activating passthrough the encoded surround sound from your source is passed through to the toslink connection without decoding.

Another question you may be thinking about is "then why do games not support passthrough?". This is because game-sounds are mixed live based on the gamers actions. While a movie has a predefined audio track, the sound from a game depends on many variables. Live mixing and encoding is needed. Mixing is done by the CPU, but encoding requires certificates (that must be bought before you may support it). Only if you use a sound card that supports the live encoding of surround sound, you can hear surround sound while playing games (if using only Toslink).

Home cinema/theatre

You may ask yourself why Toslink works with home cinema surround sets. I answered this question in the previous paragraph. The reason is that when you play a DVD movie (or bluray) the audio stream is predefined and encoded. All you have to do to make it work with surround is activate passthrough mode and you have decent surround audio. The following drawing displays how simple it really is.

Description of drawing: You only need one audio connection for decent surround sound from your home cinema set. This is were Toslink has only improvements over analogue connections, and no disadvantages. Due to the digital interface the amount of noise is mostly depending on your amplifier and the cables to your speakers, excluding many other factors. Lots of possible sources are excluded.

A different situation is when you watch TV and have it connected to your surround set by Toslink. In this case it depends on both the TV source signal and the capabilities of your TV to encode surround sound, like the sound card capabilities (supported features). Therefore many TVs only support stereo audio over the Toslink interface. (Also note that Toslink does not support the HD audio codecs).

How about combining Toslink with analog connections?

An obvious disadvantage of this interfacing is the amount of cables. You need 6 cables for analogue 5.1 sound and in addition the Toslink connection for 'passing through' the encoded DTS and DD signals if your source has them. However, this setup does enable you to enjoy surround sound in all cases. Of course, noise and interference depends on the interface that is active at that moment.

Description of drawing:

I hope the drawing is clear and does not need much description. There are 'a lot' connections needed. In addition, since you use two different interfaces in parallel, you need an amplifier that automatically switches its source, or at least makes it easy for you to switch between analogue and Toslink inputs manually. There is also a relatively large amount of cables needed.

The solution: HDMI connection

So, of all the previously mentioned interfaces, none is ideal. They each have their own advantages and disadvantages depending on the situation, mainly your sound card and your amplifier. Now, prepare for the wonder that is audio over HDMI!

For starters, the connection is really simple. It's only one cable, that is available everywhere, and it is almost impossible to connect in a wrong way. Simply connect an output of the source (PC or DVD/Bluray player) to an input of your audio set. If your amplifier has an HDMI output, simply connect another HDMI cable from that connection to your TV. And that's it! All possible audio and video connections are made!

Description of drawing: I hope this drawing makes it clear that all settings are made by the source (PC or bluray player). This works perfect as the HDMI cable communicates bidirectional and I have yet to encounter a system were the settings were not automatically detected correctly. In Windows, simply select how many speakers you have connected and it's done. Your sound card is actually not doing anything anymore (and I've disabled mine in the bios).

The advantage of HDMI is that the bandwidth is enormous. There is enough to passthrough all currently available encoded audio streams like DTS and DD, but also their newer HD versions. Master audio, no problem! Up to 8 channels (for 7.1 surround) can be transferred over HDMI uncompressed (PCM)! This means loss-less digital audio transfer all the way to your amplifier in every single situation I can currently think of.

There is only one minor disadvantage I have currently experienced, and that is that if you use a display (monitor or TV) with a resolution higher than supported by the amplifier, you either have to accept the lower resolution or use a second connection to your display. Using a second display connection will result in Windows acting like a second display is connected, while it actually is only the audio amplifier.

Conclusion

1st - So my preferred connection for both PC and home cinema should be clear by now; use HDMI!

2nd - For a home cinema setup, Toslink may be sufficient for your expectations.

3rd - For a gaming setup, get a soundcard with live surround encoding and use Toslink. But seriously; better invest in an amplifier with HDMI.

4th - Last option for a cheap-ass gaming setup, accept stereo over Toslink or accept the noise added when using analog connections.

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