rotary switch vs pots

[fredouille]

Hi all

I have never seen a rotary switch to replace pots on tube amps..

I'm use of this on neve channels strips, I never good any bad contact..

any reason not to use rotary switches outside the costs and the big job to wire resistors ?


by the way is somebody can explain how to split log value into x resistors, would be great to know the maths there.

[cdemike]

Orange amps often come with rotary switches for the "FAC" control. I borrowed the design for a recent Marshall-style build to similarly switch V1 coupling cap values.

by the way is somebody can explain how to split log value into x resistors, would be great to know the maths there.

Are you referring to determining equivalent resistance of parallel resistors? If so, the formula is: 1/total resistance = (1/R1) + (1/R2) + (1/R3) + etc.

[maxkracht]

any reason not to use rotary switches outside the costs and the big job to wire resistors ?

I think cost is a main factor, along with little benefit. You see stepped attenuators in hifi and studio gear where you are looking for: lower noise, precision between channels, greater control over specific volume settings, ability to recall precise settings, and probably a few other things I'm not thinking of.

Arguably, none of those matter for the average guitar amp and there are other places to spend time and effort making improvements. Pots are good enough for the majority of applications. Adding balanced i/o to your guitar, pedals, and amp would be cool too, but it would be a massive pain and wouldn't improve that much.

[fredouille]

Orange amps often come with rotary switches for the "FAC" control. I borrowed the design for a recent Marshall-style build to similarly switch V1 coupling cap values.

by the way is somebody can explain how to split log value into x resistors, would be great to know the maths there.

Are you referring to determining equivalent resistance of parallel resistors? If so, the formula is: 1/total resistance = (1/R1) + (1/R2) + (1/R3) + etc.

resistors are selected 1 by 1 as far as I understood, the question is how to split 1M ohm LOG in into x positions, keeping the LOG. LIN is easy you cut pot Resistance / number of steps

[fredouille]

any reason not to use rotary switches outside the costs and the big job to wire resistors ?

I think cost is a main factor, along with little benefit. You see stepped attenuators in hifi and studio gear where you are looking for: lower noise, precision between channels, greater control over specific volume settings, ability to recall precise settings, and probably a few other things I'm not thinking of.

Arguably, none of those matter for the average guitar amp and there are other places to spend time and effort making improvements. Pots are good enough for the majority of applications. Adding balanced i/o to your guitar, pedals, and amp would be cool too, but it would be a massive pain and wouldn't improve that much.

I agree it is more a question of feeling.. and recalling exact settings... precising is not the point on Neve channel strips but they all have such rotary switches.

I was also thinking that it might give better contacts... especially the closed version, no dust. a bit like oil closed pots

[maxkracht]

precising is not the point on Neve channel strips but they all have such rotary switches.

Tell that to anyone trying to work in stereo, or to quickly recall a whole board between recording/mixing sessions...


I suggest you consult google, or take a pot with your preferred taper and measure the 12 or 24 positions you like.

https://islproducts.com/design-note/pot ... ter-taper/