@dbdicker - You've said "negative signal" and GND together a few times. In an RCA interconnect from your pre-amp, the GND wire does not carry a separate "negative signal" that can be separated from the "positive signal" using y-connectors. There is only one signal for each channel. Search a couple articles on balanced/differential vs. SE. No need to re-type it all here.
The manual does say that the amp can be run mono balanced using the RCA INPUTS. What you still need is balanced signal to feed the inputs. So, you need a pre-amp with a balanced output as @6L6 has said. Or, if you really must use the same pre-amp, and you really must run balanced, you can do as 2pico has suggested.
re: advantages. No way for any of us to know if you're current or voltage limited. I doubt either, but it's possible. It may not sound better or help at all over standard monoblocks or even a well-built stereo pair in one chassis. It is very system dependent.
In general - Parallel may work well for systems with lower impedance speakers. Bridged may work well for systems requiring higher voltages to get the SPL desired. If you just could not get your music loud enough before a single F4 clipped and/or before the drivers distorted to the point of making music unlistenable or your ears bled - then bridging could help
If you already have 2 F4s, why not try parallel? It's easy, and you can do it with your current pre-amp. If you love it - awesome. If you're not happy and have a really good reason to want balanced - cross that bridge later.
Despite of my crappy english, lack of knowledge, I feel there is some confusing in this story. Respondents, I think, didn't recognise that you are talking about this configuration:
My opinion, this will not work in your case, as you described above.
Moreover in F4 article, there are parallel mono and balanced mono operations, not bridged, if I'm right.
ItsAllInMyHead - very good points, well said.
Dbdicker - you’ve touched on something in your last post, “easier to drive with less preamp gain.”
The whole gain and voltage swing thing is always confusing in regards to F4, because it has no gain, and needs the preamp to do everything. So whatever voltage your preamp can output, that’s what you’ll get at your speakers. Some preamps can spit fire, some have almost no gain. Irrespective of connecting the F4 stereo, balanced or parallel, you will get out only what you put in. (Now of course the F4 can add a bucket of current and run whatever speakers you connect to it...)
So the next question is what preamp do you have?
But ultimately, I'm going to want to try it bridged. Is that really impossible without a balanced signal from the preamp?
Those sound neat!
You’ll likely be fine - the actual amount of power people use is much, much less than they think.
You’ll need something to convert SE to BAL. Transformer or an active phase inverter.
No - I refer to this picture in the F4 manual -- where Nelson specifically states that either XLR or RCA single ended connectors can be used to BRIDGE.
And I believe the schematic above will not work as it shorts the phases together......although I'm not sure, that's why I'm asking!
Mono Parallel Operation
In mono parallel operation, you can achieve up to 100 watts output into a 2 ohm
load. The amplifier is driven by a single-ended source, through the two RCA inputs
in parallel. The easiest way to do this is through a male RCA cable going into one of
the RCA inputs with a jumper between pins 2 and 3 of the XLR input connector, which
parallels the two inputs. This jumper is supplied with the amplifier.
For parallel operation of the two channels as one, you must connect the outputs left
positive to right positive either at the connectors themselves or by “bi-wiring” the
loudspeaker with two sets of cables. Remember that the positive outputs have a red