Which switch for Rangemaster input cap mod? DPDT On-on?

[brianh]

Stupid newb question:

For a Rangemaster clone, what kind of switch is needed to be able to switch between two value input caps?  Say, one value for humbuckers, one for single coils.

I'm guessing a 6-pole On-On DPDT toggle.  This way I could put a cap at each "end" and connect from the center poles to the board.

Can this be accomplished with a SPST?

Thanks guys.

[RickL]

It'll work with a spdt, in fact it will work with a spst. To use a spst hardwire the small cap in and use the switch to add the second cap in parallel. Caps in parallel add their values (i.e. 0.01uF in parallel with 0.1uF equals 0.11uF).

Another option (which I did on my Rangemaster) is to use a spdt centre-off switch to give yourself three choices - the hardwired cap plus two different choices of parallel combinations.

[petemoore]

Find your small value input cap sound.
 Add parallel capacitor to the input capacitor, until it = the 'fat' sound you want.
 Use an spst or better [meaning more unecessary lugs for this purpose] switch to defeat the larger cap at the before the input side <ll [that's where I put the switch].

[brianh]

Another option (which I did on my Rangemaster) is to use a spdt centre-off switch to give yourself three choices - the hardwired cap plus two different choices of parallel combinations.

Hi Rick,

That sounds like a good idea.  I think I'll go with that wiring.  Which cap values did you wind up going with?

thanks!
Brian

[brianh]

If I did use a DPDT to wire up three caps, would this be the way to go about it?

thanks again

[Hal]

yup....
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=26107
same question :-D

[RickL]

I don't remember which values I used for the input caps. If I was starting from scratch I would use original cap value, 2 times original value and 10 times original value and tweak from there.

[brianh]

Thanks, guys.

Whoops, I missed that post when I did a search.

I think I'm going to try .0047uf + .01uf + .047uf to start.

[GreenEye]

This makes me want to build another rangemaster, this time with a toggle.  Yet another one on the long to-do list.

[Mark Hammer]

Whoa, camel.  I said, I said, Whoa camel.  WHOA!!

The switching you ought to use will be a function of how you expect to use the cap variations.  If you think you can reach down between songs, on a stage, plugged in, and flick a switch without a loud pop, then avoid rotary switches and parallel caps.

Yes, parallel caps WILL help you to achieve different tones, but the problem is that if a cap has one end lifted when not in service, there is no way for the charge stored in it to drain.  Close the switch to place the cap in parallel and there will be a loud pop from the "jailbreak" all those electrons have when they can finally get somewhere.  Parallel caps will be fine if all you plan to do is switch when the unit is bypassed, but if there is any risk of you flicking a switch that others will be forced to listen to at high volumes, you need another solution.

The most problem free arrangement is to use series caps that always remain in circuit.  By selectively shunting them with either a toggle or rotary switch, you can change the effective capacitance value in a pop-free method.

The only downside to this is that the math and parts-value planning is a little trickier, since series caps are calaculated the way parallel resistors are.  A common approach to solving this problem, though, is to use a centre-off (on-off-on) SPDT to leave 3 caps in series or selectively shunt combinations.

Okay, now giddyup camel.  I said giddyup, camel, GIDDYUP!! :lol:

(Maybe one day we'll see a Bugs Bunny and Yosemite Sam cartoon where Sam plays a roadie)

[brianh]

So doing it as I have pictured above would cause a pop when switching.  

I can't visualize how you have explained it with a SPDT.  Would you be able to put together a quick drawing by any chance?

[AL]

Great horny toads, a trespasser, gittin footprints all over my desert.  :mrgreen:

http://www.nonstick.com/sounds/

Thanks for the info and the laugh Mark.

AL

[Hal]

mark - could pulldown resistors be used to prevent popping?

I never really thought about that problem, only the practical switching methods.

[Mark Hammer]

The nicest illustration of doing this is with the schem for the modded Hollis Zombie Chorus that Tomboy has on his site ( http://www.stud.uni-karlsruhe.de/~udaqa/ ).  He implemented the switch I suggested for changing the clock rate from 2 ranges (as John Hollis originally had it) to 3 ranges, using 3 caps and a 2PDT centre-off switch.

[brianh]

So like this?

An engineer friend helped me along!

[Mark Hammer]

Yes, OR no.   :?  :lol:

The switch can be used to either shunt 1 vs 2 of the caps, or to shunt 1 vs another of the "extra" caps.  The choice would depend on what cap values you wanted to achieve, and what the values of the extra ones were that you added.

It seems like you have the general idea, though.

In retrospect, it may well be possible to use a rotary switch to switch parallel caps in and out, if you used a multi-pole switch and used one of the contact sets to drain off unused caps.  I haven't worked out in my head whether it is feasible with, say, a 6-way 2-pole switch though.

Personally, I usually find the 3 choices provided by a simple SPDT centre-off to be just about right.  The fact that it results in just enough variation for minimal cost and a small footprint, only adds to the pleasingly minimal machining you have to do to work with them.

[brianh]

Using that wiring, could I achieve three values of around .005uf, .01uf. and .05uf?  I think that would be a nice, wide range.

I guess I'm still not completely sure which caps are "working together" with each of the 3 positions on the switch.  

I think when the leftmost "on" is selected, it's all three caps:

1/C1 + 1/C2 + 1/C3.

Past that (if I'm even correct about that), I'm still lost a bit.

[birt]

i used a rotary switch with 9 caps on it

[Mark Hammer]

Nine is fine, although whether the tonal differences between any two adjacent cap values is actually audible is quite another thing.  I should point out that I have nothing against using rotary switches or parallel caps.  However, in gigging situations where people want to twiddle a switch or knob without first turning the volume down on anything, pop-free setups are areal help.

One thing I would be interested in hearing more about from others is the capacitance value where pops start to become truly objectionable.  Keep in mind that the pop is the sound of stored current finally having somewhere to go, but the amount of current stored will depend on the capacitance value itself.  You can pretty much guarantee that a 10uf cap will let you know that it has had one end lifted, but 10pf caps are unlikely to produce much pop at all, if any.  So, what is the inflection point in the curve?  What is the zone where capacitance starts to produce truly noticeable pops?

[birt]

Nine is fine, although whether the tonal differences between any two adjacent cap values is actually audible is quite another thing.  I should point out that I have nothing against using rotary switches or parallel caps.  However, in gigging situations where people want to twiddle a switch or knob without first turning the volume down on anything, pop-free setups are areal help.

One thing I would be interested in hearing more about from others is the capacitance value where pops start to become truly objectionable.  Keep in mind that the pop is the sound of stored current finally having somewhere to go, but the amount of current stored will depend on the capacitance value itself.  You can pretty much guarantee that a 10uf cap will let you know that it has had one end lifted, but 10pf caps are unlikely to produce much pop at all, if any.  So, what is the inflection point in the curve?  What is the zone where capacitance starts to produce truly noticeable pops?

the differences are very audible, but the switch is not meant to be switched during a song.
there are 9 cap values because the differences are so big and if someone wants me to build a rangemaster they can choose what cap(s) they want when they test mine.
the caps i used are:
.001, .002, .0047 (normal cap), .01, .02, .047, .1, 2.2 and 20 uf

switching while its on mkes some pops but those pops are not very loud.