Spdt output volume switch?

[slashandburn]

Im still here. Ive been working on that customary "dumb newbie" question. Ive tried searching about to no avail, wondering if im doing something stupid here.

Instead if a volume pot, can i use a switch by simply putting a different value resistor on each throw and having them all meet at the output?


It works just fine on the breadboard, im not overlooking anything? Having each throw meet at the same point wont cause me any issues long term? Do the resistors that lead back to the unselected throws have any effect on the circuit?

[blackieNYC]

It's a good idea if you've. ID'd the obvious lack of flexibility.  One for unity, one for boost.  You might want to have a trimpot in there to find the perfect values. 

The unused resistors ain't gonna hurt anybody if they are disconnected at the one end. But you don't need to have unused resistors. Your switch can select between resistors, or better perhaps is to have the switch add the 2nd resistor to the first. Just make sure you have a voltage divider that functionally works like an output pot set to a point somewhere in the middle.  One end to ground, one going to the output of the circuit, and a junction between them that goes to the output. Then a 2nd configuration where the values are slightly altered. Start with a 100 k pot to find these values.  This way you'll maintain the impedance that the output of your effect circuit sees.
Let me see if I can do this:
GND---WWWW-o-WWWWW-o-effect output
                           ^                   ^
                            I                   I
Switch chooses here.    Or here.   Then goes to output jack.

[slashandburn]

Thanks! Normally i'd chuck a pot in there, but i dont have a small enough value amd im limited for space.  i really just want "full volume" and "quiter" anyway so a switch would solve my problems.

I nearly went for a dpdt wired as a bypass, (resistor path for quoter, bypass for full volume but realised thats probably overkill.

A spdt works I just wanted to check I wasnt breaking any fundamental rules. It seems too easy. Usually that means ive missed something or forgot something basic.



So if i had the space, i could use say a single pole 6 way rotary this way for 6 preset volume levels? Not sure why I would, a pot would be cheaper and more flexible but it would work?  

*edit* heres that Doh! Moment. This is essentially just the same this as switching between diodes for clipping, but with resistors for volume? Meaning i could use switches instead of gain pots for "preset" gain levels?

Second edit:Ah i see what you're doing i think. So in one position it meets resistor  it meets resistor B and resistor a acts is set up as a path to ground and in the other position it meets resistor a+b in series and still has a route to ground? 

[PRR]

> i could use say a single pole 6 way rotary this way for 6 preset volume levels?

The classic "good!" way to set gains is with a 41 position bar-brass switch and a mess of fixed hand-wound resistors. Hugely expensive. Modern audiophiles use lesser switches and resistors. Still expensive. Here's a basic model using the common low-price switch: http://glass-ware.stores.yahoo.net/trstat.html

[slashandburn]

Oh wow. With one of these I could spend the next two years anally deciding on perfect resistor values for one those before inevitably deciding one day (when I cant find my notes or something) just to run with a pot instead!

[PRR]

> next two years anally deciding on perfect resistor values

At least.

And you said "im limited for space". The smallest rotary switches are about the size of small pots. Anyway you have to get fingers on a knob. And the really small switches and pots are pretty expensive (everybody is limited for money). So a switched attenuator is not the right answer for this problem. In fact switched-"pots" are very rare for music Creation, even on hi-price gear. Music creators want the wide range and infinite settings of a pot. Switched attenuators are found in radio control rooms and in hi-fi systems, where the signal level is already nearly right and only needs minor close-enough correction.

As you said, if you can decide on just two settings, a toggle switch can be smaller than a pot.