Everyone seems to be under a serious misunderstanding of how a balanced input, or a balanced
amplifier, WORKS.
With an unbalanced input, or an unbalanced output, or an unbalanced (normal) amplifier, you have one signal.
In an unbalanced cable, that one signal goes through one wire.
In an unbalanced (normal) amplifier, that signal is amplified and sent to the output.
With a balanced input, you have two signals that are equal/identical but out of phase.
When you add two signals together that are equal but out of phase you get the same signal, but at 2x the level. (You add them by subtracting them - it's an algebra thing; 1 minus -1 = 2.)
In the context of a connection, if any noise gets picked up in the cable along the way, it will be the same for both wires in the cable.
So, when you subtract them at the other end, you get twice the signal, but the noise cancels out. (That's why balanced connections are very good at rejecting noise.)
With a balanced
AMPLIFIER, you have two identical amplifiers, amplifying two equal/identical but out of phase signals.
With an amplifier, the noise thing probably
WON'T work (because noise in an amplifier tends to be random, so the noise in the two channels probably
WON'T cancel out like the noise in the two wires.)
HOWEVER, odds are that the two amplifier channels will distort pretty much the same way, and, when you subtract them, this
distortion tends to cancel out.
This will give you lower overall distortion (it will also change the distortion spectrum since some harmonics cancel out better than others).
Forget about the idea that "the wrong polarity signal will damage something" - the signals are all AC, and all based around zero volts.
The "issue" is that, if you were to send the same signal to both inputs on a simple balanced amplifier, what you'd get is.....
NOTHING (1 minus -1 = 2, but 1 minus 1 =
ZERO).
In a "dead simple balanced system", if you connect an unbalanced source to your balanced input, depending on what adapter you use and how you wire it, you'll get either half power or nothing at all.
(You probably won't hurt anything, but you won't get
ANY of the benefits you paid for,
AND, at best, you'll get half power.)
Since nobody wants that, we've made sure that it doesn't happen.
A phase splitter simply takes an unbalanced input signal and creates a "flipped" version of it to drive the second amplifier channel - which actually works fine.
(You get all the benefits of the balanced amplifier. You don't
HAVE a balanced input, so you don't get those benefits, but you don't lose anything.)
However, we use a rather more elegant method, which has other performance benefits.
Our dual differential inputs actually allow each incoming signal phase to contribute to the signal going to each amplifier channel/phase.
With a balanced input, this gives you all the benefits you'd expect, and a few extras.
And, with an unbalanced input, it generates the two out-of-phase signals needed to drive each of the amplifier channels.
(The added benefits involve maintaining better balance and doing a better job of cancelling distortion - so you generally get lower distortion with either type of input.)
Adapters work in various ways.
Some older adapters (and some expensive current ones) actually have a transformer inside that convert the unbalanced signal to a real balanced signal.
However, because the original signal is unbalanced, they can't "undo" any noise already picked up in the cable.
So, while they provide a "proper balanced signal", which will work with even very basic balanced amplifiers, there are all sorts of drawbacks.
(All transformers cause some distortion, they may pick up noise from outside sources, and even halfway decent transformers tend to be quite expensive.)
Most modern adapters that go from unbalanced to balanced simply connect the unbalanced input to one of the output pins, and connect the other output to ground.
This method is simple, doesn't add any noise or distortion (but you may only get half power with some very basic balanced amplifiers).
HOWEVER, the inputs on
OUR fully differential amplifiers work just fine with this sort of signal, and there won't be any loss of quality - or power .
Most modern adapters that go the other way (from balanced to unbalanced) simply connect the positive signal from the balanced input to the unbalanced output and ignore the other signal.
This gives you the full "quality" of the balanced signal, but
NOT any of the benefits of a balanced connection - because you don't
HAVE a balanced connection.)
Note that both of these adapters have many virtues..... they're totally passive, don't add any distortion or noise, and basically don't make the situation worse in any way (they're also
VERY inexpensive; often around $5).
They simply allow you to make a normal unbalanced connection between two devices, and work very well, for example, if you need another unbalanced input or output, but all you have available is a balanced one.
Note, however, that the adapter doesn't magically make an unbalanced connection into a balanced connection.
So, assuming your source device has only unbalanced outputs, and your amp has both kinds of inputs, there's no benefit to using an adapter instead of simply plugging your unbalanced cable into the unbalanced input on the amp.
Likewise, using a modern adapter on each end of a balanced cable, to connect two devices with unbalanced inputs and outputs with a balanced piece of
wire, doesn't gain you much of anything.
(It's not a balanced connection just because you used a balanced cable...)
(Some of those old adapters, which included transformers in them, actually could convert between balanced and unbalanced connections. However, because of the drawbacks I mentioned, they don't make much sense today - and I'm not even sure where you could find one to buy lately. Even with a very expensive one, the quality losses due to the transformer itself would almost certainly far outweigh any benefits of being able to use a balanced connection.)
I have a pair of RCA to XLR adapter cables.
If the XLR inputs of my XPA-1 power amps have their own phase-splitters (and it would seem that they'd have to - to prevent wrong-polarity signals from damaging the balanced circuitry), then an unbalanced signal would be converted to balanced at the input circuit of the amps.
I
think that the adapter works by leaving the ground pin as a ground & then sending full-range unbalanced signals (in mono) to both of the signal pins of the XLR connector. The amp's inputs, if they're unable to deal with negative signal on the positive pin or positive on the negative pin, just "throw away" the half of each pins' signal that they don't need - leaving a balanced signal to supply the amplifier circuitry.
But I could be wrong - Mr. Levkoff - How does this work?
