Does anyone know how to add an output cap selector switch to a PCB when the output cap is on the PCB? I'm thinking like the Circle Electric V828 pedal where the PCB has the stock value and the switch ups the cap value. Is it alternating between two different caps or adding a second cap in series?
Does anyone know how to add an output cap selector switch to a PCB when the output cap is on the PCB?
- Thread starter REGGAE
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pricklyrobot
Well-known member
What’s the stock capacitance value, and what value do you want to achieve with the switch?
If you’re trying to get a higher value, wire your switched cap in parallel (as caps in parallel just sum together)
If you’re trying to switch in a lower value, you might want to go series (caps in series are calculated using the reciprocal method), but it’ll probably take a little effort to find the right values that combine to what you want.
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The other option here would be, if for example your stock capacitance is 10uF and you want your alternate value to be 5uF, you put a 5uF on the PCB and a 5uF on a switch (in parallel). So you get the 5uF alternate value when the switch is ‘off’ and the 10uF stock value when the switch is ‘on’.
If you’re trying to get a higher value, wire your switched cap in parallel (as caps in parallel just sum together)
If you’re trying to switch in a lower value, you might want to go series (caps in series are calculated using the reciprocal method), but it’ll probably take a little effort to find the right values that combine to what you want.
Conversion Calculator Series and Parallel Capacitor | DigiKey
Calculate the total series and parallel capacitance of a circuit using DigiKey's Series and Parallel Capacitor calculator.
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gonzo
Well-known member
The caps would need to be in parallel not in series. You could get a double throw switch and just have two wires run to the board cap. Then add any caps you want to add to the value. In series the caps will lower value. Like this but omit the middle cap and pretend it's the board cap. Change the values as you like.
The stock varied between 3300pF to 4700pF. The switch is to take the output cap up 0.1uF.
pricklyrobot
Well-known member
Given those values, I’d just wire a switched .1uF in parallel with what’s on the board.
The difference between actual .1uF vs. .1033/.1047uF should be fairly negligible.
The difference between actual .1uF vs. .1033/.1047uF should be fairly negligible.
What @pricklyrobot said.
Also. There can be some advantages of switching in parallel as you will always have a cap in circuit, never fully breaking the circuit. That will result in no breaks in audio when switching and minimize the pop in some circuits. It also means that if the switch fails, the pedal will still work.
Is there a resistor to ground after the input cap forming a filter? Posting a snip of the schem would be nice.
Also. Keep in mind further HPF and decoupling caps in the circuit will add low frequency roll off. So, if you're doing something like bassify-ing a klone, altering some of those values could be beneficial.
Take the BMP and bass big muff ass an example. Same circuit but they literally added a 100n cap in parallel with every 100n decoupling cap.
Say you have 4 caps, 1 input(input decoupling) and 3 other decoupling caps. Say they're all 47n stock. Labeled C1-4.
You can use an additional pole switch and switch both the input cap and one mid circuit, let's say C3. Increase the other 2 to the larger value.
So C2 and C4 to 100n. Now, decrease the "stock" value of C1 and C3 from 47n to 33 or 22n. Switch a 100n in parallel with C1 and C3
This will give you similar roll off across the whole circuit as the stock version being closer to the -3db point of those filter as the stock version all while allowing more bass through the circuit as a whole(when switched into the "mod" position).
Your compensating the lack of two poles by starting the roll off a little higher. There's going to me a minor change in amplitude across a few dB (1/3-1/2 of an octave) around that stock filter point but it's a tradeoff to allow more bass through in the other mode.
Of course, breadboard or socket and use your ears(or simulate).
Also. There can be some advantages of switching in parallel as you will always have a cap in circuit, never fully breaking the circuit. That will result in no breaks in audio when switching and minimize the pop in some circuits. It also means that if the switch fails, the pedal will still work.
Is there a resistor to ground after the input cap forming a filter? Posting a snip of the schem would be nice.
Also. Keep in mind further HPF and decoupling caps in the circuit will add low frequency roll off. So, if you're doing something like bassify-ing a klone, altering some of those values could be beneficial.
Take the BMP and bass big muff ass an example. Same circuit but they literally added a 100n cap in parallel with every 100n decoupling cap.
Say you have 4 caps, 1 input(input decoupling) and 3 other decoupling caps. Say they're all 47n stock. Labeled C1-4.
You can use an additional pole switch and switch both the input cap and one mid circuit, let's say C3. Increase the other 2 to the larger value.
So C2 and C4 to 100n. Now, decrease the "stock" value of C1 and C3 from 47n to 33 or 22n. Switch a 100n in parallel with C1 and C3
This will give you similar roll off across the whole circuit as the stock version being closer to the -3db point of those filter as the stock version all while allowing more bass through the circuit as a whole(when switched into the "mod" position).
Your compensating the lack of two poles by starting the roll off a little higher. There's going to me a minor change in amplitude across a few dB (1/3-1/2 of an octave) around that stock filter point but it's a tradeoff to allow more bass through in the other mode.
Of course, breadboard or socket and use your ears(or simulate).
cdwillis
Well-known member
It's a little more of a pain, but if you wire it like this all the caps will have a path to ground and it should prevent popping even betterThe caps would need to be in parallel not in series. You could get a double throw switch and just have two wires run to the board cap. Then add any caps you want to add to the value. In series the caps will lower value. Like this but omit the middle cap and pretend it's the board cap. Change the values as you like.
Deleting an OP ina knowledge based forum like this one is generally frowned upon @REGGAE
Part of the great things about forums vs modern social media etc is the knowledge archive portion allowing others years later with the same question to easily find the answer(when they actually search). Deleting the original question makes that a no go.
Part of the great things about forums vs modern social media etc is the knowledge archive portion allowing others years later with the same question to easily find the answer(when they actually search). Deleting the original question makes that a no go.
If I had a nickel for every time someone asked a simple question on a forum only for them to get thirty pages of responses that did everything but answer the question, I'd buy the whole internet just to shut it down.
Robert
Reverse Engineer
The correct answer was in post #2, the first reply to your thread. Post #3 even included a wiring diagram.
It doesn't matter how/where the capacitor is located in the circuit, if you want to increase it's capacitance you need to add another capacitor in parallel that gives the sum needed.
The only thing missing here is someone offering to hold the soldering iron.
Yeah I'm sorry, but we're not going to do that after folks have taken the time to answer the question.
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