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Kayfun coil wrap

Selecting capacitors with toggle switches    Rick Viola 2-18-2011

No matter what values you choose, you cannot wire a 3 position switch to yield 3 values that increase sequentially. This may not be a problem, but it would be more user friendly if for example in a filter circuit, the toggle could be labeled low, medium then high.
I had seen a switch in a catalog called a SP3T (single pole, triple throw). These are sometimes referred to as DP3T or just as "on-on-on". Figure G shows the contacts in the three positions.

Normally a jumper is added by the end user for the purpose of having one input and 3 outputs.
Well, I thought that was very interesting. Especially since they did not cost more than a DPDT, (or just a little more)

Figure H shows how you would normally use a SP3T switch.

So, as in figure J, you could wire 3 caps to the 3 output paths and Voilą! You can have any cap value you want for any switch position. 

I knew there had to be something more. After a little thought I realized the idea  in figure K. This uses 3 caps, all the same value. It sequences from low, medium to high value. All in parallel, to just the bottom cap, to all in series.
I like it. you just have to buy one value and you get a range from 1/3 the value, to one times the value to 3 times the value.

Figure L is 3 caps with one of them external (or from In to Out on the switch) to result in 1, 2 and 3 times the value.

Source  example of SP3T toggle: Mouser part # 612-100-L1111 toggle described as DPDT ON-ON-ON.
Digikey
450-1536-ND

TV antenna, 4-bay bowtie

 

Crunch Box schematic with lower current draw
Final drawings as of 6-16-2013, verified and working.
6/27/13 added reference to Presence control and alternate parts.
10/23/13 added lower noise values in red and R1 option.
11/01/13 Updated schematic and wiring showing volume options.
 
Bandwidth measurements, 3db:
Controls CW unless stated. Input generator attenuated for before clipping:

All controls CW: 400-2600Hz (original 420-2500Hz)
Gain at 1/2: 400-2600Hz (same as original)
Gain CCW: 20-1600Hz (same as original)
Tone at 1/2: 400-2300Hz (original 400-2200)
Tone CCW: 200-1600Hz (original 280-1500Hz)
 

 

This is with Presence control added. The red knob is a toggle switch cap.
With tone pot wire at the top of the presence pot as shown,
more highs is CCW on the presence pot.
I am still not convinced a presence control is worth the trouble.

Wire used is 24 AWG stranded Teflon
 

Parts List
These are the parts I used but there are alternates at Mouser that will be fine with appropriate lead spacing.


Alternate source for PC board is mcmelectronics.com  part 21-114
 

Wiring
This is a tight fit.
If installing the Presence control, longer lead caps for C10 and C11 are helpful.


Crunch prototype Demo Here
Final Build Demo Here
 
 

For reference, this is the original Joyo clone schematic with their reference designators:

 

 

Cry Baby modified for no distortion if Hum buckers overdrive the circuit.
R10, R8 and R7 are chosen to center the signal swing better. The signal top used to clip way before bottom.
R9 is 2K for typical slight mid boost. R15 and R18 for gain without distortion.
R17 for higher Q factor talk mod and C4 value only as high as it needs to be.
 The added 300 ohm resistor in series with C4 prevents a distortion at low frequency,
All is sounding well with plenty of gain and no unintended distortion when I strum hard.
If the output buffers are overdriven , R18 can be increased to about 100K, compromising with lower output signal.
I may tweak this now and then and change the date.