Changing buffer size on RME Fireface on MacOs Sierra 10.12.6

[unguitar]

Hello,
I'm more at ease with pcs so forgive me for such a question.
How do I increase buffer latency to allow cpu to perform a better vst processing?
thanks

[cfillion]

Enable "Request block size" and type the desired value in Preferences > Audio > Device.

[unguitar]

thank you, this is what I did already but although I've set it to 20000 (!) I can see no improvement at all...

[cfillion]

Try with a power of two. Does the information at the right of the menu bar reflect the setting change you made?

[unguitar]

thank you for the advice, I didn't remember latency was displayed at the top of the frame.
From there it looks like the maximum buffer size can be reached is 3072, even when you type higher values.
Anyhow, it looks like there's something weird.
At the cost of becoming boring, I'm posting a few snapshots showing the same project with all fx set to processing or processing off and with 512 or 3072 spls.
The thing is that, even with all effects set to off, the transport is not fluid at all.

[unguitar]

here are the screenshots

[-nicolas-]

1024 or 2048 are power of 2.
These are already high values, there is rarely a need to go above.