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At what length do balanced cables become necessary?

post #1 of 19
Thread Starter 
Hello,

I'd like to buy a stereo amp and feed it with audio from a DAC (plugged to a laptop). The amp will probably be in the same room as the laptop, but not right near it. I assume the cable length I'll need will be of about 7 to 10 meters. Is it too long for a regular unbalanced cable, and will the signal be degraded? Should my equipment work with balanced cables or would it be overkill at such lengths? I also thought about digital outputs, but this would require a A/V receiver, as stereo amps with digital inputs are almost non existent, and I don't need an A/V receiver.

Thanks.
post #2 of 19

It's actually not so much cable length as other issues.  Signals don't degrade faster in unbalanced cables, but there can be noise issues.  Signal degradation in cable is primarily related to driving them with a high source impedance and working into a high termination impedance at the receive end.  Under those conditions cable capacitance can affect high frequency response.  However, if driven from a low source Z, as it would likely be, 10 meters of wire capacitance should have minimal effect.  Balancing cables won't help that problem, though.

 

The entire and only reason for balanced interconnects is the improve noise immunity.  To take advantage of a balanced cable it must be driven with a balanced output and received by a balanced input with high common-mode rejection.  No common AVR has that capability.  Just using balanced wire does nothing.

 

AVRs almost always have digital inputs in the form of coaxial or optical.  

post #3 of 19
Thread Starter 
Thanks jaddie. You said signal degradation should be minimal at 10 meters of cable length, but will the signal gather noise at that length? In the end, which route should I take: balanced or unbalanced?
post #4 of 19

What exactly is the equipment?

post #5 of 19
Thread Starter 
I have none of it yet. I'll need a DAC for the laptop, a stereo amp and some good speakers.
post #6 of 19

Well, that's pretty vague. What are you trying to accomplish?  What is the purpose of this system?

post #7 of 19
Thread Starter 
The purpose would be to play music that is stored on my laptop's hard drive on the hifi system in my living room. The laptop will be in one part of the room, the amp in another, that's why I'll need to run up to 10 meters of cable between them. The amp will have other components plugged to it, especially a CD player and a tuner; so it will not be exclusively dedicated to playing music from the laptop, but also intended as a standalone system. I want to control the playback from the laptop, and use the software music player that I want on it. Occasionally I'll watch movies or play games and I'll want to use the speakers of the hifi system as well for that. That's why I don't want a music server or a network music player; they would be controlled with a remote, not from the laptop, and would be unable to play anything but music, whereas I want to feed audio to my amp from other applications as well. The system will be stereo only, not 5.1 or "home cinema" because I intend to use it primarily for music, and only occasionally to watch movies.

On the laptop side, I will also have headphones. I already have an unbalanced headphone amp (Cute Beyond), so the DAC will either have to have unbalanced outputs for my current headphone amp, or an integrated headphone amp.
Edited by Cutter - 5/6/13 at 5:44am
post #8 of 19

Often in situations that require longer signal cables, the components at each end are powered from different AC circuits.  This (multiple AC circuits) is an excellent source of noise problems.


Edited by Speedskater - 5/7/13 at 1:46pm
post #9 of 19
Thread Starter 
But would this be resolved by using balanced cables?
post #10 of 19
Quote:
Originally Posted by Cutter View Post

The purpose would be to play music that is stored on my laptop's hard drive on the hifi system in my living room. The laptop will be in one part of the room, the amp in another, that's why I'll need to run up to 10 meters of cable between them. The amp will have other components plugged to it, especially a CD player and a tuner; so it will not be exclusively dedicated to playing music from the laptop, but also intended as a standalone system. I want to control the playback from the laptop, and use the software music player that I want on it. Occasionally I'll watch movies or play games and I'll want to use the speakers of the hifi system as well for that. That's why I don't want a music server or a network music player; they would be controlled with a remote, not from the laptop, and would be unable to play anything but music, whereas I want to feed audio to my amp from other applications as well. The system will be stereo only, not 5.1 or "home cinema" because I intend to use it primarily for music, and only occasionally to watch movies.

On the laptop side, I will also have headphones. I already have an unbalanced headphone amp (Cute Beyond), so the DAC will either have to have unbalanced outputs for my current headphone amp, or an integrated headphone amp.

Ok, getting closer.  What's the laptop, how is the music stored, what software do you play from, and what are the other applications you wish to feed audio from?

post #11 of 19
Quote:
Originally Posted by Cutter View Post

But would this be resolved by using balanced cables?

Not with cables alone, you need components with balanced ins and outs too, or you'll just have balanced cables used as unbalanced cables.  Connecting two unbalanced devices always results in an unbalanced cable, regardless of cable design.  Connecting a balanced device to an unbalanced device directly results in an unbalanced connection.  The only way to achieve a balanced connection is with two balanced devices and balanced cable.  

 

Unbalanced devices can be made to us balanced interconnects with add-on balancing devices.  There are many, of varying designs, cost and quality.  It would be best to confirm the need first.  It's likely there'll be no need for balanced interconnects. 

post #12 of 19
Thread Starter 
Quote:
Originally Posted by jaddie View Post

Ok, getting closer.  What's the laptop, how is the music stored, what software do you play from, and what are the other applications you wish to feed audio from?
I don't have the laptop yet. I'll probably buy a Samsung Series 9 or something similar. The music will be stored on the laptop's hard drive, most of it in MP3 format at a high enough bitrate for the compression to be transparent, the rest of it in FLAC. I'm using foobar2000 for music and VLC for movies, but I don't want to depend on the software. Basically, anything that can be fed to a soundcard should be potentially playable on the living room's amp, even audio from a web browser (in case I want to play music from websites such as Grooveshark), or audio from games such as Battlefield 3.
post #13 of 19

 Had to dig for this, but this is one of the better papers that explains what's going on with interconnects, and more importantly, saves me from writing it all again.

 

http://www.rane.com/note110.html

post #14 of 19
Quote:
Originally Posted by Cutter View Post


I don't have the laptop yet. I'll probably buy a Samsung Series 9 or something similar. The music will be stored on the laptop's hard drive, most of it in MP3 format at a high enough bitrate for the compression to be transparent, the rest of it in FLAC. I'm using foobar2000 for music and VLC for movies, but I don't want to depend on the software. Basically, anything that can be fed to a soundcard should be potentially playable on the living room's amp, even audio from a web browser (in case I want to play music from websites such as Grooveshark), or audio from games such as Battlefield 3.

You should be aware of a very simple and elegant solution, but with a few limitations.  If you use iTunes, you can play out to AirPlay devices.  One AirPlay device you may want to look into is the AirPort Express, which provides an analog and digital audio output to a stereo device.  You can play your library out to several AirPlay devices at once, control the playback from your PC, and control individual volume levels for each device.  You'll use ALAC rather than FLAC, but there is no difference in quality.  You won't get audio out of other applications like that, though.  But it's a very elegant, high quality and simple solution.  All you need is the AirPort Express, no DAC, no cables.  

 

If you want to play movies to a TV and use your stereo system for sound, consider an Apple TV.  It is also an AirPlay device, and can play out videos you have in your iTunes library from your laptop, as well as navigate your library directly from an on-screen menu on your TV.  Also very elegant, and cheap, no DAC, no cables.

 

With AirPlay, you also have the ability to play wirelessly from a portable iDevice, and use that same device to control your laptop playback.  With AppleTV you can also play videos from your iDevice to your TV, as well as share the screen, play out photos, music etc.  None of this may matter to you right now, but having that capability and discovering uses for it later raises the value of the solution.  

 

I'm not sure why you don't want an AVR. Many of them offer some advantages you may want, and any of them will operate in two-channel stereo mode just fine.  For example, some laptops provide HDMI outputs, either directly or with a simple adapter, which would let you connect your laptop to your AVR for video and audio playback.  10 meters is ok if you get a good quality HDMI cable.  This would let you use VLC, foobar, and any audio from the PC that way too, though honestly, that combination is nowhere as elegant as the Apple TV or AirPlay/iTunes solution, and playing all audio from a PC is really a bad idea.  People think they want to do it, then when they do, it gets old very fast. 

 

If you're dead-set on doing it the hard way, a DAC at the laptop, stereo amp 10 meters away, and no integration to a TV, that's possible too, just get the unbalanced wire you need and give it a try.  It will probably work just fine, and if not, you'll have to deal with an alternative solution of some kind. 

post #15 of 19
Thread Starter 
Quote:
Originally Posted by jaddie View Post

Had to dig for this, but this is one of the better papers that explains what's going on with interconnects, and more importantly, saves me from writing it all again.

http://www.rane.com/note110.html
This document is difficult to understand for me because I'm a total stranger to the theory of signals and electric currents. What it seems to say is that plugging a balanced cable to two "balanced" ends doesn't guarantee that the signal will be noise-free. This document was first written in 1985 though, maybe things have changed a bit since then.
Quote:
Originally Posted by jaddie View Post

You should be aware of a very simple and elegant solution, but with a few limitations.  If you use iTunes, you can play out to AirPlay devices.  One AirPlay device you may want to look into is the AirPort Express, which provides an analog and digital audio output to a stereo device.  You can play your library out to several AirPlay devices at once, control the playback from your PC, and control individual volume levels for each device.  You'll use ALAC rather than FLAC, but there is no difference in quality.  You won't get audio out of other applications like that, though.  But it's a very elegant, high quality and simple solution.  All you need is the AirPort Express, no DAC, no cables.  

If you want to play movies to a TV and use your stereo system for sound, consider an Apple TV.  It is also an AirPlay device, and can play out videos you have in your iTunes library from your laptop, as well as navigate your library directly from an on-screen menu on your TV.  Also very elegant, and cheap, no DAC, no cables.

With AirPlay, you also have the ability to play wirelessly from a portable iDevice, and use that same device to control your laptop playback.  With AppleTV you can also play videos from your iDevice to your TV, as well as share the screen, play out photos, music etc.  None of this may matter to you right now, but having that capability and discovering uses for it later raises the value of the solution.  

I'm not sure why you don't want an AVR. Many of them offer some advantages you may want, and any of them will operate in two-channel stereo mode just fine.  For example, some laptops provide HDMI outputs, either directly or with a simple adapter, which would let you connect your laptop to your AVR for video and audio playback.  10 meters is ok if you get a good quality HDMI cable.  This would let you use VLC, foobar, and any audio from the PC that way too, though honestly, that combination is nowhere as elegant as the Apple TV or AirPlay/iTunes solution, and playing all audio from a PC is really a bad idea.  People think they want to do it, then when they do, it gets old very fast. 

If you're dead-set on doing it the hard way, a DAC at the laptop, stereo amp 10 meters away, and no integration to a TV, that's possible too, just get the unbalanced wire you need and give it a try.  It will probably work just fine, and if not, you'll have to deal with an alternative solution of some kind. 
Versatility would be one of the most important criteria for me, and not being able to use any other application than iTunes is an eliminatory drawback of Apple's solutions.

Playing and controlling playback from a mobile device sounds fancy indeed, but it is not an exclusivity to Apple's AirPlay; foobar2000 has components providing remote-control and UPnP features, and there are apps for Android that can take advantage of these features.

A/V receivers are not a solution I want to consider at the moment: first they are more expensive, which means that at a given price, an A/V receiver will have either worse sound or less features - or both - than a stereo amp. Second, sending an undecoded signal to the A/V receiver will necessarily cause some problems when the audio track won't be encoded in a format that the A/V receiver recognizes. I fear it will involve perpetual tweaking, like having to convert everything to PCM on the fly from the laptop, and I'll be increasing the already endless list of threads titled "My digital output doesn't produce any sound"...
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