Multiple inputs caps on a rotary switch...pulldown resistors for each cap?

[skiraly017]

Or can I get away with one resistor for all? Thanks!

[Michael Weidenauer]

I'd put one pull down resistor in front of the switch and connect the switched sides of the caps with 10M or 22M resistors and ground one of them also with a 10M or 22M resistor.
The 10M/22M resistors won't affect the sound but will minimize switching noise.

If you don't care about the clicks and pops then one resistor should be enough.

[blooze_man]

I had a varitone in my guitar without using any pulldowns(it's kindof the same type of thing), and the pops even when playing loud were barely noticable.

[jefe]

Here's something I've wondered and asked about, but I don't think I've ever gotten a clear answer: Doesn't it depend on which type of rotary switch you use? There are two types of switches: "make before break" contact, and "brake before make" contact. The "make before break" switch makes contact with one circuit in the switch before breaking contact with the other circuit. So, while you're turning the rotary switch from position 1 to position 2, there is a brief moment when you have two caps wired in parallel... but never a moment when there is NO cap in the circuit.

On the other hand, when you have a "break before make" type of switch, there are moments between switch positions when there is a cap - then NO cap - then a cap is plunked back in to the circuit. That seems like a good recipe for loud pops between switch positions, no?

I hope I'm making sense here. I'd really like to know what others think of this. Are pulldown resistors necessary when using a "make before break" rotary switch?

[skiraly017]

Here's something I've wondered and asked about, but I don't think I've ever gotten a clear answer: Doesn't it depend on which type of rotary switch you use? There are two types of switches: "make before break" contact, and "brake before make" contact. The "make before break" switch makes contact with one circuit in the switch before breaking contact with the other circuit. So, while you're turning the rotary switch from position 1 to position 2, there is a brief moment when you have two caps wired in parallel... but never a moment when there is NO cap in the circuit.

On the other hand, when you have a "break before make" type of switch, there are moments between switch positions when there is a cap - then NO cap - then a cap is plunked back in to the circuit. That seems like a good recipe for loud pops between switch positions, no?

I hope I'm making sense here. I'd really like to know what others think of this. Are pulldown resistors necessary when using a "make before break" rotary switch?

I understood you perfectly and wondered the same thing. Awhile back I built a Neutron and used whatever rotary switch I had lying around and it popped when switching between HP/BP/LP. Later I bought another rotary switch and the popping stopped. Maybe I should revisit the project and see what happens.

[jefe]

I understood you perfectly and wondered the same thing. Awhile back I built a Neutron and used whatever rotary switch I had lying around and it popped when switching between HP/BP/LP. Later I bought another rotary switch and the popping stopped. Maybe I should revisit the project and see what happens.

Cool, I'm glad someone understood what the heck I was trying to say.  

I built a big muff with switchable components in the tone stack. I used one of these plastic enclosed switches from smallbear, no pops:
http://www.smallbearelec.com/Detail.bok?no=46

He also lists this open type as "non-shorting", I wonder if that's the same thing as "break before make"?:
http://www.smallbearelec.com/Detail.bok?no=117

[PRR]

> Doesn't it depend on which type of rotary switch you use?

Not much.

With make-before-break, yes one cap discharges into the other. This still pops, typically 1/3rd to 2/3rd as bad as break-before-make.

The real problem is the caps sitting with NO drain resistor for minutes or hours. If there is DC on one side and no-DC on the other side, they will charge-up to full DC, and POP when connected to the no-DC point.

If at least one contact is always connected to a load which drains DC (pot, grid resistor, etc) and caps are low leakage (film), the cheap trick is to put 10meg _across_ adjacent contacts. 6 contacts only needs 5 resistors and no ground lug.

[R.G.]

The right way to do this is to
(1) connect all capacitors to a single pull-down resistor of maybe 1M
(2) wire a 4.7M to 10M resistor in series with each capacitor
(3) the non-capacitor ends of all the series resistors goes to the pole of the rotary switch, and this also connects to the input of the effect circuitry.
(4) each throw of the rotary switch connects to the junction of one capacitor and it's high-resistance series resistor.

The rotary now "shorts out" the series resistor for the selected cap. The others appear in series with a high resistance, and do not contribute significant signal.

[PRR]

Not really about the 12 cents saved. Sometimes the "cheaper" plan works better on the switch.

When in doubt: take your vitamins, say your prayers, and do it the Right Way.

[R.G.]

I actually thought about the "right way" comment after I hit send. 

There are many ways. Each has its own problems. Just the use of high value resistors causes increased noise. The way I listed takes more resistors and can be tougher to wire, as all of the resistors won't go on the switch. The throw-to-throw wiring relies on the pole to hold the DC state of all the caps, so a faulty switch position can cause the next position to either direction to pop - albeit faintly unless it's left in the faulty position a long time, and in spite of such open connections being rare. One more resistor always connecting the pole to the chain-of-throws would fix that, as well.