balanced or unbalanced??

[saywhat]

So Im looking at buying an amp and preamp combo and you can hook the preamp to the amp via balanced or unbalanced Connections.
Which should I use and Why? Whats the difference?
thanks for any explanations

 

[jinjuku]

Balanced if you can. For starters you get CMNR (Common Mode Noise Rejection).

 

[lsiberian]

I personally like having both options in a pre-amp.

 

[psbfan9]

This is from the ATI website. Seems they're saying not all balanced inputs are created the same. I'm at loss as to what ATI means by 'discard most benefits' though.

While many amplifiers have balanced, XLR-type input connectors, most simply convert the balanced input signal to unbalanced in the first amplification stage and discard most of the benefits of a balanced connection in the process. Not Pure Balance® amplifiers. ATI’s Pure Balance® amplifiers keep the signal balanced all the way from the XLR inputs to the speaker outputs.

 

[Ampdog]

Saywhat,

Advantages as said, but it is not always certain what you get.

Balanced lines are classically used with long leads as in PA, where the possibility of spurious noise pickup exists, as in electrically noisy environments. In such instances the noise picked up cancels because balanced line signals are out of phase. There is mostly no danger of this in domestic set-ups. Then the "discarded benefits" refer to carrying on with balanced signal progress through an amplifier, where every stage is 'balanced', i.e. having the same topology on the negative side as on the positive; something like push-pull. (It is a little difficult to explain without a diagram.)

In my view this may or may not be an advantage. The semiconductors on either side of 'neutral' - npn and pnp types - are normally not exactly the same, and also there are tolerances. Any good design takes care of that. A balanced mode usually gives a better noise/hum rejection, but the audible advantage might be academic if the non-balanced design is good. Many amplifiers generate a balanced topology from an un-balanced input anyway as said above - but that is not necessarily a disadvantage. Such 'generated' balanced topology is usually pretty accurate, whereas one is not sure if both signals are exactly the same in balanced mode from a source - hopefully they are! (Generated balanced topology inside an amplifier is there for the sake of noise/hum rejection.)

Not embellishing further, theoretically there is an advantage in going fully balanced, but in practice it does not always turn out that way. Let me say, I would not "saddle the horse" in search of balanced or pay a handsome price for that. Too much depends on what goes on inside a particular amplifier or system.

Sorry for the complexity. To sum up: If you are not in a particularly noisy environment, and lacking knowledge of the exact detail of a system .... I hope you get the drift!

 

[Swerd]

Very good answer Ampdog! Thanks

Balanced connections are commonly used for live audio and in recording studios for microphones with long cables. Long cables (30 feet or more) carrying microphone voltage (1-3 mV) signals can pick up noise induced by electromagnetic interference, among other things. Balanced connections along with the differential circuits required on the electronic gear can cancel out this noise. Read about it here: Balanced audio - Wikipedia, the free encyclopedia

It seems that balanced connections have become fashionable for connections between preamps and amps, and these usually come with higher prices. The voltage levels between preamps and amps are much higher than microphone level, roughly in the range of 0.1 to 5.0 volts (100 to 5,000 mV). So it is likely that interconnects at this level are less prone to induced noise, especially if they are less than 30 feet long. I think that standard RCA interconnects between a preamp and amp are fine, unless you have an unusually noisy environment with high levels of EMI or RFI.

It probably is not worth paying a premium price for a preamp or amp with XLR connections.

 

[jinjuku]

I think you also get another 3dB of Dynamic Range in an all balanced setup.

The thing I've been considering is a +60/0/-60 power supply. I would just like to have one to say I'm cool But my setups to run off of a dedicated circuit each.

 

[Swerd]

I think you also get another 3dB of Dynamic Range in an all balanced setup.

Providing full differential circuits and connecting with balanced cables only between a preamp and amp will not accomplish this. That additional 3 dB in dynamic range comes only if the entire audio signal chain has full differential circuits and is connected with balanced cables. This means full differential circuits from a sound source like a CD player or DAC, continuing through a preamp and finally to the amp. Achieving that 3 dB extra headroom is not insignificant, but it will cost a premium.

If the entire audio system is done completely balanced, that is maintaining balanced operation from input to output, then in theory, all common mode distortion in the system would cancel, providing potentially superior audio playback. This would require a four-channel DAC, a four-channel preamp, a four-channel power amp (or two stereo power amps), summing the signal at the speakers. Of course, the amount of improvement actually realized will depend on how much distortion was originally there to cancel.

I wonder how many people have such a system .