Unbalanced and Balanced output voltage

Great question, Raul. You beat me to it. I was thinking of posting this today.
If someone can also answer the "leg" of XLR that I discussed a couple of weeks back. I have also noticed the same thing as Raul. 2V vs 4V. Is it that:
1.Some manufacturers do not prefer the "leg" approach and provide the "total" of "2V+2V" = 4V as the XLR out to the preamp
OR
2. Some manufacturers provide the figure of "2V" at each "leg" of the XLR to the preamp?
The reason I want to find is, when I switched from RCA to XLR between the preamp and amp, I got [substantial] gain. And some folks did mention that the gain "doubled". So whatever volts were going from preamp to amp - are they sent twice over + and - "legs" of the XLR?

Yes basically the negative volts from ground to ngative doubles the voltage.
With twice the voltage from the preamp you get twice the level.. out of your amp.
The amp is still limited to the rated full output.
So if the amp can produce a maximum of 250 watts. it does not matter if it is connected via RCa or XLR, the limit is still 250 watts. But with XLR, you will hit that limit sooner via the preamp volume control. just because it is sending more voltage with XLR.

Balanced is no magic bullet to increase amp power...

Elizabeth,
Thanks for explaining. I was aware of the amp's output, being limited to the spec. It was about a new CDP (in future) with XLR in my system that I was thinking about.
So does it mean that if the CDP outputs 2V per leg, that is equal to 4V to preamp? And then this 4V becomes 8V when it is sent from preamp to amp connected via XLR? This could mean trouble, as it would lead to too much gain in the system.
Yes, I do have to reduce the position of the volume knob when connected via XLR. When using RCA (between preamp and amp), my volume knob was at position 12-14 (depending on recording level) out of the available 24 positions. Now I have to go down to 7-8 to listen to comparable volumes.

Milpai,

The idea of balanced circuit is to separate negative signal from positive and from the ground. In conventional RCA unbalanced connection we only have one signal terminal and ground while in balanced circuit we have Negative, Positive signals and ground.

If RCA output in the same component let's say CD-player is specified 2V, than for balanced it's +2V on positive 'leg' and -2V on negative 'leg'. The total output voltage is sum of magnitudes giving 4V. Very simple math.

Thanks,

In my case is the other way around. I am using a Sony SCD-XA5400ES connected to a passive amplifier. From the RCA the volumen is OK but when I connect the XLR I have to turn the volume almost to maximum to get good sound. I do not think this is good because I believe that the impedance is also high. The Sony has 2 vols in both RCA and XLR. I wonder if the problem is the preamp that does not have any gain...