Why i should buy a scope ( maybe not ) ?

[nsubulysses]

Exactly. Excessive screen node capacitance makes the amp feel stiff and lifeless - at least to me.

for what kind of amp? a not that loud clean-ish amp?

just asking because it seems like high gain amps and also some loud basss amps a lot of the time tend to have 100uf screen node capacitance or sometimes even more.

Would you recommend NOT a large screen node capacitance for amps in general or only certain types of amp depending on playing style. just curious

[tepsamps]

Exactly. Excessive screen node capacitance makes the amp feel stiff and lifeless - at least to me.

What capacitor would put at this place ? To have an idea ...

[tepsamps]

for what kind of amp? a not that loud clean-ish amp?

just asking because it seems like high gain amps and also some loud basss amps a lot of the time tend to have 100uf screen node capacitance or sometimes even more.

Would you recommend NOT a large screen node capacitance for amps in general or only certain types of amp depending on playing style. just curious

I do mostly hi gain amps, and soldano, as a source of inspiration for me, use 220 µF for plates, 110 µF for screens after the choke, plus 50 and 10 µF in the preamp.

[Helmholtz]

What capacitor would put at this place ? To have an idea ...

In a 2 x 6V6 amp I would not go higher than 47µ but probably settle at a lower value after listening tests. There is some interdepence and dynamic interaction between filter nodes, and "optimal" cap values are influenced by the whole amp/power supply structure including PT (sag), rectifier type, choke value/placement or screen dropper and total amp power. SE power amps generally require better ripple filtering/higher filter capacitance than PP amps.

The preferred screen cap is best found by playing the amp.

[Chuck H]

I do mostly hi gain amps, and soldano, as a source of inspiration for me, use 220 µF for plates, 110 µF for screens after the choke, plus 50 and 10 µF in the preamp.

In the above design your use of 10uf in the preamp actually has them in parallel pairs. So your preamp nodes are 20uf. Just noting that.

The screen node won't benefit much in additional ripple rejection with the larger value. Maybe a difference of a tenth of a volt with 100uf instead of 22uf. And then there's sag with instantaneous current demands. The larger cap will hold a little steadier, but then recover a little slower. The smaller cap will undulate a little more with discharge/recharge that must be happening in real time with current. But the overall advantage to the larger cap is tiny. The disadvantages would be greater inrush current, slower recovery and additional expense.

Here's an overlay using Duncan's PSUD2. Stepped time recording a basic amplifier power supply after a delay of four seconds, recording for two seconds, stepped at five seconds.

60ma/75ma plates with a 100uf and 8ma/11ma screens with 100uf in teal and 22uf in red. I did the overlay with MSPaint.

[Helmholtz]

The charge/discharge time constants at the screen node define attack and release times of screen compression.

[Helmholtz]

Would you recommend NOT a large screen node capacitance for amps in general or only certain types of amp depending on playing style.

Just my personal preference for more blues oriented playing styles. I feel that large filter caps tend to make the power amp respond more like a SS amp or a PP amp with triodes.
Bass players and metal players may prefer the tighter bass with larger cap values, though.
Let your ears decide.

[g1]

Would you recommend NOT a large screen node capacitance for amps in general or only certain types of amp depending on playing style. just curious

Depends on how much screen glow you're willing to accept.