Simple, in-line volume control

[scwhiteley]

This seems like a simple question with a simple solution. However, as usual, the more research I do, the more confused I become.

I've built a few simple amps in the past using simple IC's and other people's schematics. So far I've had pretty good results. Currently, I'm building a simple stereo for my bedroom. I'm doing this because A: I think I have all the parts in my basement, B. I'm cheap, and C: It's fun...!

Sorry for rambling, but my question is this:

One of the speakers will be a satellite, in its own box, and I'd like it to have its own volume control. (There will also be a master volume control on the amp.) This is the speaker that will rest on my desk, and I want to be able to control its volume individually. So how do I add a volume control into the speaker line? Can I use a simple potentiometer, as in the amp itself (my first thought)? The research I've done indicates that this could not only be detrimental to sound quality, but could actually damage the amp due to improper impedance on the line...?

Now, I'm not a hardcore audiophile, but I do care... so I guess I'm a softcore audiophile. All I really want is a sweet stereo in my bedroom with a speaker on my work desk that has its own volume.

If you've made it this far, thanks for reading my long-winded post.

Regards,
S. Chad Whiteley

[audioguru]

A vacuum tube amplifier is damaged when its load resistance is too high. A solid state amplifier does not care if its load resistance is too high.

A series volume control is called a rheostat and it can reduce the volume but not to zero.
An amplifier has an extremely low output impedance that damps the resonances of a speaker. But with a resistance in series with a speaker the damping is ruined and the speaker might sound "boomy" at its low frequency resonance and sound "'shrieky" at its high frequency resonance.

An old method was "an L-pad" which also ruins the damping of resonances.

Go to a home entertainment equipment store. They sell a switched transformer that mounts in a wall box that will work pretty well as a speaker volume control (but not for a sub-woofer).

[Hero999]

Use a small 120V variac?

Probably not ideal but better than a series resistor.