4700uF is the capacitor size right ? I see Schiit is very obsessive about it. Do you think it can affect the sound ?
The 2x polar 4700μF are in anti-series so form a 2350μF bipolar capacitor.
One does not want the amps frequency response and output R to change too much.
R load must be above >8Ω Knowing the Verum 1 and DCA headphones exist we may want to drive these too.
Z out = < 0.1Ω. We don't want that to rise much at lower frequencies but are going to have to allow this.
20Hz = -0.05dB. We will going to have to poor some wine into the glass here.
Also the phase will shift in the lower bass but will be gradual and not severe.
What happens at 20Hz when an 8Ω load is used at 20Hz when a 2350μF is used:
Output Z increases to 3.3Ω (at 100Hz= 0.67Ω) which still isn't something to really worry about but when connecting the Verum we get -3.3dB at 20Hz and -0.8dB at 100Hz.
So there are audible consequences with such loads.
Assuming most headphones are above 20Ω we lose just -1.3dB at 20Hz which is not unacceptable.
With this capacitance a 32Ω headphone will be -0.5dB at 20Hz which is acceptable and inaudible.
This only gets better for higher impedances.
So 2350μF is a good enough value to not have audible impact with the vast majority of headphones IF one has to use output capacitors.
When one has to use output capacitors and uses the Verum 1 or DCA Noir (or similar model) and does not want 20Hz attenuated more than 0.5dB you will have to use much larger capacitors but in such case I would simply buy a post 2021 L30 (which is the correct thing to do anyway)
For speaker amps, having to drive lower impedances and depending on the design a single 4700μF or 10000μF can already be enough.
The reservoir caps value is another thing though. This can be smaller than the output capacitor depending on what feeds the those caps (regulated or unregulated DC, switched mode or 50Hz mains single phase rectified), what the internal output Z of the supply is and what ripple is allowed under maximal load as well as the amount of feedback in the amp, the output current limit.
So the needed buffer capacitor value near the output devices is totally design dependent and there is an optimal value for each design.
Bigger ≠ always 'better'.
One of the argument in the subjectivist world is that the PSU and the capacitor capacity/power in reserve (uF value) have an impact on sound.
They also claim all cables affect the sound and some even claim amps sound better with a sticker placed on strategic locations on the amp.
Of course, as seen above, output capacitance and very low impedances affect sub-bass extension when too small in value.
The value of the reservoir cap depends.
One has to realize that cap is not directly in series with the audio signal as there is active components in series too that determine the output signal.