I have an integrated tube amp that has a power button, and a multi-position switch for CD, SACD, etc. That's it.
Some audiophiles say thats all you need if you have a proper amp and speaker.
In the '70s, when Crown was a big and respected name, their Crown 150 amp had an On/Off button, but I don't recall which knobs/switches the preamp had.

Eric G.