Ignoring the philosophy of simpler being better...
If you have identical gain elements in parallel, summed to one signal afterwards, you are literally just 'adding' gain together... right?
Couldn't this be used to avoid gain headroom issues in lower-supply-voltage applications?
For example, using ''several'' AMZ mosfet boosters in parallel to drive a power amp, or whatever.
In general, amplifiers in parallel multiply the current gain, not the voltage gain.
They do not even multiply the current gain, generally. Yes you get twice the available output current, but you have to supply twice the input current to get that.
In general: voltage gain and current gain are un-changed. Input impedance and output impedance are *half* (and that low input Z may be an issue in guitar-cord work). Power output is double _if_ the load impedance is reduced. (Same voltage, double current.)
> avoid gain headroom issues in lower-supply-voltage applications?
Many fine pedal-amp topologies will output 80% (peak-peak) of the supply voltage. 2 or 4 more in parallel might buy you 82%. With simple(*) circuits you can do this well easily but can NOT exceed the battery voltage.
(*) There ARE tricks. Merlin has published a self-bootstrapper which does 12 or 15 V p-p on a 9V battery. Not simple; though not too extravagant if you CAN'T use a taller supply voltage.