fader question.

[japmn]

Ok, here goes...

Mic/line pre = amplifier

eq also can be seen as an amplifer

fader = ... (I think only attenuator, right? wrong?)

do the faders on consoles control amplifiers or only attenuate levels?

by looking at the board it seems you can get upwords of 10 to 15 dB of gain
at the fader... sometines even more.

am I missing something. are faders not just resistors.

is this gain somehow created by the summing amp? magic?

or... are their actually amplifiers other than preamps and eq on each individual channel?

I have asked this question many times and usually get "um... never thought of that... I have no idea?"

I'm just curious.

Japmn

[The Scum]

The fader itself is just a variable resistor, as you surmised.

But it's usually followed by an amplifier (called the fader buffer), so the output impedance of the channel to the mix busses doesn't change as the fader moves. The fader & buffer amp are usually designed to work together, to offer some degree of boost above unity gain.

At least, that's true for modern consoles...long ago, when amplifiers were noisy & expensive, there were no fader buffers, so the faders were indeed attenuators.

You might also check out http://www.forsselltech.com/summing%20buss.htm for some discussion of gain from summing amplifiers.

Byron Jacquot