Botón

[Alfonso]

What do you mean by knob?

[María José]

El pomo de una puerta, but it could mean other things...that I'm not going to explain here.

[Alfonso]

Originally Posted by Gemma

El pomo de una puerta, but it could mean other things...that I'm not going to explain here.

Thanks, Gemma.

Originally Posted by Tomisimo

Another observation: I've noticed that Spanish speakers sometimes use botón for a knob that can be turned.

I never use botón for pomo.

[Tomisimo]

What do you call these in Spanish. These are all knobs in English.

[CrOtALiTo]

An observation, a button in my country, we don´t say button to the zipper, button here is only a bottun or a bellboy.

[María José]

Originally Posted by Tomisimo

What do you call these in Spanish. These are all knobs in English.

Not a clue. Pomo is only for doorknob. Could this be mandos, interruptores? I'm not sure.

[Rusty]

Mixer = mesa/unidad de mezcla

I found all these words used for the knobs, controls, buttons (all synonyms), in no particular order:
control de volumen/tono/etc.
botón de ...
interruptor de ...
mando de ...
regulador de ...
perilla de ...
tornillo de ...
potenciómetro de ...
dial de ...

[Tomisimo]

Good research Rusty. A mixer can also be a mezcladora or consola. A note concerning potenciómetro, it doesn't refer to any knob; it refers specifically to a potentiometer also known as a pot to electronics people. Thanks for the great options!

[Rusty]

Originally Posted by Tomisimo

Good research Rusty. A mixer can also be a mezcladora or consola. A note concerning potenciómetro, it doesn't refer to any knob; it refers specifically to a potentiometer also known as a pot to electronics people. Thanks for the great options!

Yeah, I know the term potentiometer quite well, and was surprised to see that several sites used the term to refer to the terminal, o el eje que sale del potenciómetro rotatorio, to which a knob is normally affixed. These sites were written for audiophiles who know about pots, faders, and the like.

If you do a search on potenciómetro de volumen/tono, you'll see that they're talking about the knob that controls the device, not the device itself.

Here are a couple of sentences from some of the sites:
-El manejo del equipo se realiza utilizando una pantalla táctil y el clásico potenciómetro de volumen.
-... tiene un potenciómetro de tono y otro de volumen ... (guitarra Yamaha)

[Alfonso]

I have usually heard of potenciómetro to refer to what you mean, the knob. Even I use this term for my guitar. I'm not an expert at all, but I think this is the most common term in Spanish for this.
I have also heard of interruptor for a radio knob, especially if it's got and on/off item, but I think this is imprecise, although some people use it.