> I should have thought before I posted
Buz- no reason to feel silly. This difference (between loaded-pot and loaded-rheostat) is NOT obvious and has fooled many minds, even when it is pointed out.
What we often want in a Mike-Amp (I dunno what the Forssell compressor is doing) is a variable resistor that is 10K at one end, 1K in the middle, and 100Ω at the other end, to give gains of 60dB 40dB 20dB. Common audio-taper pots, wired as a rheostat, do that pretty well. Audio-taper evolved in AM radio where you need about 40dB range of gain from big/local to far/weak stations, and audio-taper gives 30dB or 40dB of usable change. Except the "10K" (mike-amp lowest gain) end winds up as the clockwise end of rotation, and most audio knobs have low-gain at the counterclockwise end of rotation.
BTW: look at most kitchen stoves. "Big flame" is usually COUNTERclockewise, and "turn down" is a clockwise rotation. So if you want to turn-up the fire and turn-up the kitchen-radio, you turn the two knobs in opposite directions. Maybe all we need to do is use kitchen-stove knobs on our straight-audio mike-amp Gain pots?
Ah, can't break soundman hand-habits. So we want a reverse-audio taper. There are only two uses for these: reverse-James feedback tone controls with gain (some Quad and Dynaco), and our vari-gain mike amps with gain control in the shunt side of the feedback network (to minimize noise resistance). Dyna is dead, Quad is either dead or far beyond where they were in 1964, and the world's demands for aftermarket generic mike-amp-pots is very small (mixer-makers special-order big cartons of pots for production and repairs).
For some unknown reason, 10K reverse-audio is often available. It will work in many mike-amps, even if they call for 5K. The difference is in the "9" to "10" range: the 5K will have 100Ω at "9", the 10K will have 200Ω at "9". What we want is something like 50Ω at "10" and maybe 100-150Ω at "9". A 50Ω fixed plus a 5K reverse audio-taper can give a smooth shift over this range, a 10K will be very "jumpy", sudden large change of gain in the "10" to "9" range. For folks who use only hot-mikes on loud acts, and never go near "10", this may not matter. For my dynamics on choir, the high gain I need is right in that crack where the gain is too "jumpy" to set accurately.
You could scale the whole network higher, to suit the available pots. But in transformerless amps, we want the shunt resistance very low, lower than mike impedance. That leads to impossibly high currents, so the compromise is to use low resistance at high gain, high resistance at low gain where noise is less important. (Even so, a 10K pot can give audibly excess noise at medium and low gains.)
And loading a rheostat just does not do what we want. The mid-point is wrong, and wiper loading does not change the curve at the extremes of rotation where we need some control. As a POT, OK, but not as a rheostat.
FWIW, I fought this concept for weeks once, trying to soup-up my parents' low-fi console stereo. I didn't have a good audio pot, so I loaded and series-resistored a linear pot every which way. Took a lot of failure-based calculation to prove it to myself.
> said anything to the Geo FX guy?
As a POTentiometer, loading can and does give a useful shift in the mid-rotation ratio. Mid-rotation on a linear pot is -6dB, and you can make it -10dB or -15dB if you want. But "1" (on "0"-"10" marking) is -20dB on a linear pot, and pretty much -20 or -22dB on a loaded-linear pot, unless you load it SO heavy that it gets pretty useless.