In a complex devices - either virtual or real - it is rarely successful to "fiddle" with advanced parameters unless you understand what you are doing and why ..... and where your goal lies.
Fractal Audio Blocks Guide, Amp Block, Power Supply Page, p. 13:
Screen Frequency, Screen Q – These set the resonant frequency of the virtual power tubes’ screen filter, and
the Q of that filter.
excerpt from Dave's Corner: Amplifier Power Supply Stages explained
Following the rectifier tube or diodes, the power supply runs through a series of large electrolytic capacitors that filter out the remaining ripple from the DC voltage, which can cause unwanted noise and other detrimental effects. A number of large filter caps are used to clean up the voltage supply before it is split off for delivery to different parts of the amp.
The size and configuration of the filter capacitors (aka electrolytic capacitors) also plays a part in determining the playing feel of any tube amp. As discussed above, all amps need some filtering to maintain relatively quiet and satisfactory operation, but amp designers can further tweak power filtering to craft a desired response one way or another.
Lighter filtering tends to induce a softer low-end response, with relatively more looseness in the feel of the amp overall. Light filtering can also, to some extent, affect the harmonic content of an amp, inducing a little dissonance and “ghost noting” when the amp is pushed hard, which can be a desirable part of any given amp’s overall texture in some instances, and undesirable in others, depending on your playing style and the tone you seek.
Heavy filtering helps to firm up an amp’s bass response while also leading to a tighter, punchier sound overall.
Makers will sometimes lean toward lighter filtering for simpler vintage-style amps that seek to replicate the sound and feel of the classics from the ’50s and ’60s. For heavier or more contemporary sounds, with thumping lows in particular, makers will usually go with larger filter caps, and more of them.
Add up all the variables, and you quickly see how the power supply stage plays a big part in shaping the personality of any tube amp. Partner it up with the right preamp and output stage for your needs, and you’re off.
