OK, what exactly IS "balanced"?
Feb 9, 2006 at 2:41 AM Thread Starter Post #1 of 70
Graz

Graz

500+ Head-Fier
Joined
Apr 3, 2004
Posts
726
Likes
15
This question has been kickin' around in the back of my mind for a while...at the risk of revealing how little I really know about this stuff, here goes...

What exactly does "balanced" mean? When I first saw the term, I was under the impression it meant:
- two separate & completely isolated mono amps, one for the right channel & one for the left channel...each of the two mono amps sport their own volume controls
- each amp has it's own completely independent & completely isolated power supply
- headphones must be wired specifically for this type of application, with each of the left & right sides feeding independently to each of the two "sides" of the amp, with no sharing of grounds as with "conventional" 'phones.

I have a hunch that the above is "close, but not quite"...and possibly describes more of a "dual-mono" setup than a "balanced" setup. Exposing my ignorance here again, but is "dual-mono" and "balanced" the same? If not, what's the diff?

Lastly, how far back up the audio chain can one go with this whole balanced scheme? Is it simply an amplification thing to "go balanced / dual-mono", or do folks even go "balanced" DACs as well?

I know I'm all over the map with this, but I'm just totally confused really...

I know it's tempting sometimes to jump in with guesses & conjecture, but I'd really like to see replies from folks who are sure of what they're talking about on this topic.

Thanks in advance!

Peace,

Graz
 
Feb 9, 2006 at 2:47 AM Post #2 of 70
Ok, I know almost as little as you about balanced, but I can point out one important thing for you. At no point in the chain should left and right share a ground. A stereo headphone has 3 terminals on the plug - left, right, and ground. Balanced connectors would each have their own.

I also know that the XLR connectors work in a pretty funky way, but I don't know enough about it to even pretend like I know what I'm talking about (and I'm usually ok at pretending I know what I'm talking about
eek.gif
) So I'm eager to follow this thread.

We need TheSloth. He just spent away his retirement on a balanced rig!
 
Feb 9, 2006 at 2:50 AM Post #3 of 70
Quote:

Originally Posted by nspindel
...I can point out one important thing for you. At no point in the chain should left and right share a ground. A stereo headphone has 3 terminals on the plug - left, right, and ground. Balanced connectors would each have their own.


Yea, I mentioned that here:

Quote:

Originally Posted by Graz
...with no sharing of grounds as with "conventional" 'phones.


Peace,

Graz
 
Feb 9, 2006 at 3:17 AM Post #4 of 70
Dual mono means separate amp board with its own separate power supply for each channel (right and left). Dual Mono does not imply separate grounds and if it's not balanced, the ground is shared. Basically, a dual mono amp is just a stereo amp with two separate single channels. Pull the plug or battery from the left channel and the right channel will still work. Benefits are better crosstalk rejection, higher channel separation and less interference between channels.

------------

For true balanced, you need four amplifiers. Two amplifiers per channel. In the dual mono or a stereo configuration you have 3 wires. One for right channel, one for left channel and one for ground. So if there's a 4V signal in the right channel, there'll be 4V on the right channel wire. Ground has always 0V.

In balanced, however, you have 4 wires, 2 for each channel. If there's the same 4V signal on the right channel, there'll be +2V on one of the wires for the right channel and -2V on the other wire for the right channel (inverting and non-inverting signal). The resulting signal is still 4V and the ground serves as a reference point.

Therefore you need 4 amp boards for balanced operation, two per channel, and in each channel, one for driving the inverting and the other amp for driving the non-inverting signal.

That's also why a true balanced DAC has four outputs: '+' and '-' for each channel. A "non-true-balanced DAC" has a stereo output (+,-,ground) and uses an opamp or transformer to convert the stereo signal into a balanced signal.

And that's why you need to recable your headphones because normal headphone cables carry '+', '-' and ground. A balanced headphone cable needs to have the four wires as described above.

To make things more complicated, it is in fact possible to have a balanced headamp but only one power supply. That'd be balanced but not dual mono. Most balanced amps, however, are both balanced and dual mono.
 
Feb 9, 2006 at 3:53 AM Post #5 of 70
saint.panda posts a very accurate account.

The only thing I have to add is regarding power supplies. Dual Mono can be a misleading term with respect to balanced operation. If you have two power supplies, then in a sense a normal balanced amplifier is Dual Stereo, as there are two power supplies feeding four seperate channels (one positive and one negative per side). The HeadRoom Balanced Max is Quad Mono, i.e. has four power supplies, one for each channel. As was said earlier, it is technically possible to have simply one power supply for the entire amp, but having one power supply per channel is the ideal way. 2 power supplies is a good cost/performance compromise.

ps: hi again nspindel. thanks for the pm!
 
Feb 9, 2006 at 3:57 AM Post #6 of 70
Quote:

Originally Posted by saint.panda
And that's why you need to recable your headphones because normal headphone cables carry '+', '-' and ground. A balanced headphone cable needs to have the four wires as described above.


Thanks a lot for this explanation...extremely helpful.

One question regarding your quote above though...

How does one cable three connections (+, -, and ground) to a headphone driver (or any driver for that matter) that only has connection for "+" & "-" ?? Or, would that in fact be FOUR separate connections ("+" and it's dedicated ground, and "-" and it's dedicated ground)?

Peace,

Graz
 
Feb 9, 2006 at 4:02 AM Post #7 of 70
I think you slightly misunderstood. He meant that a normal headphone cable has 3 cables TOTAL for both drivers (L+ R+ LR-) (at least on lower end headphones, higher end ones tend to have seperate grounds in the cable that are joined only at the jack connector). Balanced cables require 4 cables TOTAL (L+ R+ L- R-). The 5th and 6th connection on the dual XLR jacks (2*3) go to ground, and are usually connected to the shield around the cable. A grounded ground channel is not strictly necessary in a balanced amplifier however, and there is little evidence that the grounding of the outer cable shielding makes any difference. Many people consider that the ideal balanced headphone connector is the single connector 4 pin neutrik. HeadRoom use the dual XLR's, as currently the only combination 1/4" and XLR all in one connector uses the 3 pin design (allowing them to use one kind of connector that can connect to both balanced and unbalanced headphones).
 
Feb 9, 2006 at 4:10 AM Post #8 of 70
As TheSloth explained, there are 3 (stereo) or 4 wires (balanced) leading to the headphone but each driver only needs two connections (just like speakers have a '+' and '-' input).

In the non-balanced case, the ground wire is connected to both drivers and "left channel wire" is connected to the left channel and "right channel wire" to the right channel. In the balanced case, you simply have two separate wires (L+, L-, R+, R-) for each driver. No shared ground.

Frankly, the left headphone driver doesn't care if it sees 0V on ground and 4V from the "left channel wire" or +2V from L+ and -2V from L- as long as it knows that there's a 4V difference.
 
Feb 9, 2006 at 12:36 PM Post #10 of 70
Quote:

Originally Posted by TheSloth
saint.panda posts a very accurate account.

The only thing I have to add is regarding power supplies. Dual Mono can be a misleading term with respect to balanced operation. If you have two power supplies, then in a sense a normal balanced amplifier is Dual Stereo, as there are two power supplies feeding four seperate channels (one positive and one negative per side). The HeadRoom Balanced Max is Quad Mono, i.e. has four power supplies, one for each channel. As was said earlier, it is technically possible to have simply one power supply for the entire amp, but having one power supply per channel is the ideal way. 2 power supplies is a good cost/performance compromise.

ps: hi again nspindel. thanks for the pm!



Hey, thanks for responding! Graz, I told you Sloth was our man. This is quite informative....
 
Feb 10, 2006 at 11:06 PM Post #13 of 70
I Know what balanced is...
I also know it used for long cables that has more potential to collect noise on the signal, and therfore needs the Balanced solution.
But how does it improve sound quality for a 2 meter Cable ?!
confused.gif

and how does Headphones can become tru Balanced ? as far as i know they have only + and - for each chanel...
Someone care to explain ?
Great Thread BTW
eggosmile.gif
 
Feb 11, 2006 at 12:45 AM Post #15 of 70
There are some that don't believe balanced operation = improved sound quality. Look here
 
You must log in or register to reply here.

Users who are viewing this thread

Total: 2 (members: 0, guests: 2)
Back
Top