1 pot, 2 tones, switching between both tones.......

[deadastronaut]

ok, ive got 2 tone controls...but ideally i want to just use 1 pot for both tones and use a toggle to switch between..

(e.g  2 simple big muff tone controls...but on 1 pot...)

A: is this possible?

B: am i just being an awkward sod , because i know i can use 2 pots with independant tones and switch between both easily..

C: im just trying to save box top space...?... anyone done this?....

edit: not dual ganged...

[nexekho]

I'm not 100% on what you mean - d'ya mean the tone control has two potentiometers and you have one pot and a switch (thus needing some kind of resistive memory!?  maybe an ADC, some kind of register, DAC and MOSFET configured as a voltage variable resistor) or you have two totally different tone filters but want to be able to choose using a switch using the same pot on both?

[ayayay!]

Sure!  You said it's not dual ganged, right?  So you have these BMP types tonestacks, and the output of the tone control is the center lug(s).

Center tone lug out to outer lugs of a SPDT.  Done.

You could also look into doing via Push/Pull.

Edit:  Oh wait, you said not dual ganged, but I was thinking you meant dual concentric.  You mean literally only a single pot w/ 3 lugs?  

Now things get more complicated.  It can be done, but what a pain.  You'd pretty much be mounting all the BMP components on a larger switch like a 3PDT or maybe a 4PDT.  You wouldn't be saving any space.

[deadastronaut]

two totally different tone filters but want to be able to choose using a switch using the same pot on both?

yep thats it!..


@jono:  hmmm....i dont quite get that!...


edit: jono, yeah i see what you mean, i think i'll have to go down the 2 pot toggle route ...

[earthtonesaudio]

I'm in the same not-quite-understanding boat as nexekho.  If you want to independently adjust two always-on tone controls using a single pot, I think you can't possibly do so without storing a value somehow.  The modern way would be to use a PIC or uC to sample the pot value when the switch is in position A and output a control signal to tone control A, then store that value when you switch to B, etc.

On the other hand, maybe non-independent adjustment is OK, like if you have a stereo BMP with ganged controls.  In that case you basically want a dual ganged pot function... but without the dual ganged pot.    That's a little easier to do analog.  Your panel mount control could control a pair of LED/LDRs, wired inversely, for each pot you're replacing, like this.

[alfio]

Something like this (switches have to intended with common toggle i.e. 3dpt)?

http://imageshack.us/photo/my-images/440/muffswitch.jpg

[deadastronaut]

i'm still messing with the 2 tones on breadboard i don't fancy adding more stuff to it..opamps etc...and have no idea about pics etc...

this is how i have it so far...well you get the idea!... i was just looking to do away with the other pot, but there are too many connections to consider,...

i think i'll have to stick with something like this, for simplicity, the push pull is a good idea though...hmmmm...

[alparent]

what value is your pot?

Forget about the togle switch!

A pot with a push/pull DPDT switch on its back would be cool. Pull the knob....controle one tone stack......puch the knob....controle the other.

[deadastronaut]

i'm using a 47k lin for both....

[Perrow]

DA, don't forget that you'll probably want to break each tone controls connection to ground as well.

[deadastronaut]

yep gotcha.. ive got em both working fine on bread at the mo...with a toggle switching between them...it works good..

i was just trying to be economical/tight...

[slacker]

What are the component values in the the two tonestacks?
You can probably do this by switching caps or resistors in parallel or series to get both tonestacks into one, like in the Runoffgroove 22/7 http://www.runoffgroove.com/22-7.html

[deadastronaut]

ahhh i see..1 pot and a couple of switches.....i'll give that a go, cheers ian...


cheers guys...

[Mark Hammer]

If you look at the schematic for the early issue Little Big Muff, you'll see that it doesn't use a pot at all.  Instead, it uses a toggle to switch between two different tone settings, essentially the extremes of the pot settings.


Now, you probably could NOT simply wire up a pair of 100k tone pots i parallel and simply switch between the wiper of one or the other, since the two in parallel would put a combined parallel resistance of 50k between the outputs of the lowpass and highpass sections that make up the tonestack.

However, you could stick a pair of 250k or 200k linear pots in parallel without changing the behaviour of the circuit.  Or, alternatively, if you used a DPDT or 3PDT stompswitch to select between the wiper of one or the other, and lifted/engaged one side lug of each pot, that would leave your 100k tone control circuit intact without requiring the making and breaking of too many contacts.

It seems clear your goal is to make it a stompable feature, but it's actually a useful feature for toggle selection too, and no more difficult to do that way.

Nice idea. 

[Perrow]

I've got a couple of (recycled) massive switches from old KVM and printer switchers, I remember one of them being a 27P4T  switch. One of those could switch a bunch of components. I've thought about using mine in a Condor Cab Sim to switch between different setups (there's 6 resistors and four caps that should change values).

[deadastronaut]

right ive been trying this...in various ways, but if i change the value on one RC to ground it affects the other?...

hmmm...how can i get them switched to be independent  RC'S of each other?...I guess its because they share the ground?....

[slacker]

In that example if you get rid of R4 and C4 and make R3 switchable between 10k and 22k that will give you the same two filter frequencies.

The way you're doing it the two caps are always connected in parallel so all you're doing is switching between the two resistor values.

[Perrow]

right ive been trying this...in various ways, but if i change the value on one RC to ground it affects the other?...

hmmm...how can i get them switched to be independent  RC'S of each other?...I guess its because they share the ground?....

DA, don't forget that you'll probably want to break each tone controls connection to ground as well.

I could say "I told you so" but instead I say; either use the second part of a DPDT to break the ground connection of the other RC or to switch at the VOL pot.

[deadastronaut]

@ian: like this you mean?....cheers man.

@perrow: yep you did warn me...but did i listen..?..obviously not  lol...



edit: yep seems to work ok....cheers guys!...