Input Impedance selection

2

200man

Power User
WRT these selections for input impedance:
1MΩ
1MΩ+ Capacitor
230kΩ
230 kΩ + Capacitor
90 kΩ
90 kΩ + Capacitor
70 kΩ
70 kΩ + Capacitor
32 kΩ
32 kΩ + Capacitor
22 kΩ
22 kΩ + Capacitor
Auto

I have always kept the "Auto" engaged.
But as I experimented with these input impedances I noticed a "pronounced" effect on the tone.
So much so...well back up a little...I've been chasing clean tones for a while so it is easily heard.
I understand that the cap rolls off the tone and I can hear it and the higher the resistance the more brittle or clear the tonality becomes. I know the speaker plays a big role in the modeling but jeepers creepers, this setting really has an effect!

I know that the input jack on a fender amp has a little resistor/cap combo for the bright switch, but this setting is not that? But I can change the cap in the fender amp input? So if I specifically dial in an input impedance selection for an amp I need to undo whatever may be in the amp block?
 
A guitar plugged into an amplifier has an upper frequency peak, caused mostly by pickup inductance and cable capacitance.

Lower input impedance (just like lower guitar pot values) lowers the height of the peak, so it has less effect.

Adding a capacitor (or using longer cables) lowers the frequency of the peak, something like slightly backing off on a wah pedal.

This has nothing to do with the Fender bright switch circuit that adds a capacitor across the volume pot to boost treble at lower volume settings - it has most effect when volume is low, and no effect when volume is at maximum. You can modify the bright capacitor in amp settings.
 
Some vintage pedals and devices like the Fuzz Face, Boss CE-1 chorus, and early Vox and Crybaby wahs had a lower input impedance that affected their interaction with guitar pickups. Basically, the lower the input impedance, the more high frequency loss you get. In many cases this is a bad thing and is often referred to as tone sucking, but in the case of some vintage circuits, it actually contributed to their warm vintage character. Those input settings let you mimic the effect of the low input impedance of those old circuits. The Auto setting automatically sets it to match the model used in the first block placed on the grid.
 
Some also say that many classic players like Hendrix and SRV preferred to use coiled guitar cables for the same reason. The little bit of extra high frequency loss warmed up their tone in a way they liked.
 
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