Wheel for sound volume control is the best.
Because it allows you to quickly adjust sound to the desired level, increasing or decreasing.
Buttons for adjusting volume is not a suitable interface, because you
have to press it multiple times, with fixed increment. It's slow, takes
more time, more effort, and, if you hold it, it's easy to overshoot.
Logitech G810 Keyboard
[image source comcen.nus.edu.sg ]
Dell SK-8135 Multimedia USB HUB keyboard
Dell SK-8135 Multimedia USB HUB keyboard
ltbp Sven Multimedia 4004 general view 4
Gigabyte Force K7 Keyboard
, 2013 October.
Buy at amazon
This wheel is actually used as mouse wheel.
SMK-Link VP6310 VersaPoint Keyboard.
Monoprice Gaming TKL Keyboard
Monoprice Gaming TKL Keyboard