switchable cap circuit

[ssstonelover]

I added a switchable cap circuit to my master tone and it works but I get a click under certain circumstances
---If I play some chords then quickly move the switch back and forth the noise is audible. This is true when the tone knob is at "1" or some other low level.


On the other hand there is no click sound if
--tone knob is at "10". That makes sense as the tone control is almost completely out of the circuit then.
--If I let the guitar strings go silent (~5 seconds) then also there is virtually no switch noise. This is true whether the tone control knob is at "10" or at "1".

I've tried adding resistors (1Meg) but the same phenomenon occurs (no change)
--The good news is that the switch click sound is not loud, is very transitory, and to me the value of 2 caps easily outweighs the slight 'click'. My attempts at "make-before-break" are not addressing the issue, so it is somewhere else (cap loading/discharge) or the resistor value is wrong.... (too high or low). I used 1Meg resistors.

Any ideas?

This was the last iteration



Previous iteration:


Original iteration:
like above but without resistors

[JohnH]

it all looks sensible but I could imagine the crackle is anoying even if not a 'show stopper'

I think its good that the ground side of the caps is not switched. Theres no need to.

It looks like currently, the hot side of the unused cap still floats. It might be better if each cap hot wire has its own high-value fixed resistor to connect it directly to the tone pot (or switch centre lug). Then the switch is just shunting one or other of these two resistors to fully engage one cap but neither cap is ever fully disconnected and so cant build up any charge differential.

[ssstonelover]

Thanks John,

I'll add resistors to the hot side of each cap to the center hot.
--The pot is 250K, what value might work for the resistors?
--Keep the center resistor (center hot to center ground) right? It's value at 1Meg seems OK to you or should I try another value?

[JohnH]

I think that with the two added resistors, it shouldn't need the current one.

1M is ok, or theoretically could be higher say 2.2M.

If this doesn't fix it, then I cant see that much else can be done.

[ssstonelover]

I tried 2 more versions of the circuit 

This one with 3 resistors (all at 1 Meg)


This one with 2 resistors (both at 500K). I figured that more 'bleed' would keep the caps charged more so that the click sound might be eliminated when doing the switching.



No change in either case, there is a click sound (with tone pot set at "1"). At the end of the day resistors don't seem to help -- whatever the configuration. The good news is that switching rapidly between caps while the string are still in motion is pretty rare, and the clicking sound is not louder than rapidly moving the particular cheap 5-way switch on this guitar with strings still ringing.
I could be getting some switch bouncing and less than optimal contact despite the 'steady but low' contact the resistor(s) are providing...
For the record this is a new switch, so oxidation or dust should not exist...

Would DeOxit, CRC QD Electronic Cleaner, or some kind of lubricant/cleaner such as CRC 2-26 help in your opinion -- or best to call it a day and move on the next project?
Assuming this is worth pursuing, any preference on product or product properties?

[JohnH]

I'm all out of ideas based on draining of caps. If you want to try some spray on the switch, then maybe the type that sometimes helps scratchy pots could assist. I find the ones that include some lube with the cleaning solvent work best I dont know about specific products in your hemisphere tnough.

[ssstonelover]

John, I appreciate it. Perfection can sometimes be elusive.
I achieved much of my goal. I discovered the world of low cap values, such as .0033uF and .01uF, and am so far finding them better than the .022uF and .047uF values -- to my ear anyway.
I may try the same concept with a 6-way rotary switch on another guitar to further check for "ideal caps" by cross comparing even more values.

The G&L PTS (which you have written about) would also be great to try. You mention it may be especially useful on a humbucker rig, but I
would apply it to a single coil setup, normal kind of windings, so not overwound at all but not true vintage either.

[Charlie Honkmeister]

Aug 7, 2017 11:41:43 GMT -5 ssstonelover said:

John, I appreciate it. Perfection can sometimes be elusive.
I achieved much of my goal. I discovered the world of low cap values, such as .0033uF and .01uF, and am so far finding them better than the .022uF and .047uF values -- to my ear anyway.
I may try the same concept with a 6-way rotary switch on another guitar to further check for "ideal caps" by cross comparing even more values.

The G&L PTS (which you have written about) would also be great to try. You mention it may be especially useful on a humbucker rig, but I
would apply it to a single coil setup, normal kind of windings, so not overwound at all but not true vintage either.

     Perfection can be tuneable.  I'm really getting some great results with the bootstrapped variable capacitor using a buffer.  Coil switching and serial/parallel switching schemes work fine but it's a different approach than conventional passive tone and volume controls.     I'll have a new thread on this soon   if there's interest.    The old thread (albeit getting a bit dated)  is at:   Variable Resonance Pickups - Fun with Buffers


     -Charlie

[ssstonelover]

Charlie, I'd be interested. (Just saw your post, sorry)

[Deleted]

Hex Switching

as Caps sum up the more you put in parallel, can get away with using Less Caps and more options

10nF 
A 4n7F
B 12nF
C 22nF

this will give you from 10nF-48n7F (Not Caps are 10% leeway) 
Also means you an add another item for D selection or could i guess use a 56nF and have a max of 104nF!!