a cmos switching scheme for parallel distortion & other FX

[Processaurus]

This idea came to me just as I was falling sleep the other night (what, is that ill?), I like 2 in one pedals, which are often two effects in series, but with distortion lately I've been impressed with parallel sounds,  especially how the rat and big muff sound in parallel.  So the notion was to get either individual circuit when its stompswitch is on, but the option of a mix of the two when both stompswitches are on.  So here's a way to do that with a CMOS 4052 2p4t analog switch, and two spst stompswitches.  I appreciate anyone who feels like looking this over and commenting on/proofreading the design.  The ins and outs of the 4052 are biased to v1/2 as RG reccomended in his cmos switching article at Geofex to avoid distortion.  I haven't made it yet (waiting for the Rat pcb...) so no warranty expressed or implied, but its all just basic building blocks.  One thing I'm unsure of is if the switching will be too slow with the .1 caps used to debounce the mechanical switches.





I'm liking this idea for 2 in 1 boxes, where the 4 different states possible with 2 stompswitches are all usable sounds.   Whats cool is there is another 1p4t switch available on the 4052 to change things in the circuits depending on the switching state.  You could always throw in another 4052 and get even more options, like diode switching, eq changes, gain, etc. for the both on/parallel sound.  With whats there, it'd also be simple to add the option of a clean blend in place of one of the distortions, in the tradition of the sparkledrive, or do something with the routing like the muff mixed with clean sound, then that mix piped into the rat...

It is about as far from true bypass as you can get.  If that's a deal breaker, who knows, it may be possible to do it somehow with 3pdt switches, with the LED pole controlling the logic.  Or a more direct approach, using the cmos to control a relay for the bypass state.

[Processaurus]

Here's an updated schematic, the area right around the stompswitches is a little different, and is more correct for driving the CMOS logic inputs.  I wasn't sure if an LED's voltage drop between the V+ and the logic input on the 4052 as on the original would reliably be seen by the chip as a logic high state, especially if a blue or white LED was used, and the battery got low.

[trixdropd]

Though i'm no help as to this circuit, I am interested in it. Great work!!

[sean k]

Hey Processaurus, could you go through the switching options and show whats connected for each level sorta like
FX1 off, FX2 off/X0>X
FX1on, FX2off/X0>
FX1on, FX2on/X0>
FX1off,FX2on/X0>

[Processaurus]

Sure, the two footswitches act as a simple binary address for the 4052, so with the four logic states possible with them (0,0; 1,0; 0,1; 1,1)  it sets the electronic rotary switch to one of its four throws.  The truth table on the data sheet is what shows what throws are connected depending on the address, but it goes like this:

The commons (pins X and Y) are connected to 0X and 0Y respectively when the A and B logic inputs are low (the footswitches are both off), then make input A high (by turning on Effect 2's footswitch) and it connects the commons to 1X and 1Y respectively.  Make A low and B high (effect 2 off and effect 1 on) and the commons are connected to 2X and 2Y respectively, and finally if A and B are high (both effects on) the commons are connected to 3X and 3Y respectively.

A	B	On channels
0	0	0X, 0Y
1	0	1X, 1Y
0	1	2X, 2Y
1	1	3X, 3Y

[sean k]

Thankyou so much for that, I'll log that away for further reference.

Immediately I imagined using an LFO to switch the states but it would have to be an extremely slow one to be of much use. But then that would only have states 0,0 and 1,1.

I'm thinking though that a momentary switch that latches somehow, my ability says latching relays and vague theory tells me that and gates and such like where a short input high keeps the output high until a low on the input changes the out to low is what I'd want but I don't know enough about logic stuff. I suppose nows the time to start looking into it.

Why don't you enter this in the switching comp? maybe too late but it'd be a winner I think.

[Processaurus]

Immediately I imagined using an LFO to switch the states but it would have to be an extremely slow one to be of much use. But then that would only have states 0,0 and 1,1.

How about hooking your LFO or envelope or something up to an LM3915 or lm3914 to get an easy window comparator, and driving the logic with that somehow?

[puretube]

A 4013 can output 4 states... 

[j2sip]

Sorry for bumping up an old thread:)

CAn you point me to a circuit that use cmos and a momentary on stompswitch to toggle between 3 effects? I'm thinking of the posibility of using a spdt momentary on switch to switch between amp models and/or gain mode of the Sansamp GT-2 guitar effects.

Thank you.

[defaced]

How about up to eight?  http://music-electronics-forum.com/t11908/

[j2sip]

Thank you so much for the link. I'm still a noob about this things but i'm learning:)

[boogietone]

Haven't looked at the circuit yet but I do like the blue bear buffered input stage.