Pot Wiring Question

[shiner_man]

I have a vero layout for a box I want to build that says the following:

Gain lug3/lug2 connected via C16 47pf, and C17 100pf

Does this mean I solder both of these capacitors between lugs 2 and 3? 

There is also a single wire coming off the board that says:

Tone 3/Volume 3

Does this mean the wire goes to the third lug on the Tone pot and then from that lug to the third lug on the Volume pot?  Does it mean
two wires should come off the board with one going to each lug?

Finally, when it says that lug1 of both the Tone and Volume pot go to ground, should they be grounded to the back of the pots or to the
input jack shield?  Does it even matter?

I'm sorry for the beginner questions but this will only be my second build.

[jefe]

Do you have link to the vero layout? Also, if there's a link to a schematic as well, that would help a lot.

[shiner_man]

Yes.



I can find the schematic if need be.

[jefe]

I can find the schematic if need be.

Please do.

[shiner_man]

Part     Value         
     
C1       0.05uF     
C2       100pF         
C3       0.22uF         
C4       4.7uF         
C5       0.05uF         
C6       0.022uF       
C7       470pF         
C8       200pF         
C9       0.05uF         
C10      47pF           
C11      2.2uF         
C12      0.033uF       
C13      10uF           
C14      100uF       
C15      0.003uF     
C16      147pF       
POT1     100KB       
POT2     100KB       
POT3     1MA           
Q1       2N5457       
Q2       2N5457         
Q3       2N5457       
Q4       2N5457       
Q5       2N5457       
Q6       2N5457       
R1       1M           
R2       47K           
R3       10K           
R4       1M             
R5       1M         
R6       4.7K         
R7       470K         
R8       22K           
R9       200K           
R10      4.7K           
R11      22K           
R12      200K         
R13      1M             
R14      470K
R15      12K           
R16      1M           
R17      1M         
R18      47R         
SW1A     DPDT         
SW1B

[nocentelli]

I'm not sure where that schematic is from, but if you go back and read the thread accompanying Mike's layout at the other place, there is a detailed discussion about the gain control treble bleed capacitor, including input from Nicholas himself. In a nutshell, the original pedal had a 47pf across lugs 2+3 of the gain control to let high end through at low gain settings. You can add a 100pf in parallel with this to get a brighter sound - Nicholas additionally suggested adding a 5n, to really open up the treble end. I tried this with all three options on a three position on-off-on dpdt toggle:



The 47/147pf works nicely for a brighter sound with humbuckers, but I find the 5n makes the gain control a little redundant.

[shiner_man]

I'm not sure where that schematic is from, but if you go back and read the thread accompanying Mike's layout at the other place, there is a detailed discussion about the gain control treble bleed capacitor, including input from Nicholas himself. In a nutshell, the original pedal had a 47pf across lugs 2+3 of the gain control to let high end through at low gain settings. You can add a 100pf in parallel with this to get a brighter sound - Nicholas additionally suggested adding a 5n, to really open up the treble end. I tried this with all three options on a three position on-off-on dpdt toggle:



The 47/147pf works nicely for a brighter sound with humbuckers, but I find the 5n makes the gain control a little redundant.

Thanks a lot.  I guess I'll just go with the stock 47pf cap and see if that works for my setup.

Any idea about the wire that goes to Tone 3/Volume 3?

[nocentelli]

There is also a single wire coming off the board that says:

Tone 3/Volume 3

Does this mean the wire goes to the third lug on the Tone pot and then from that lug to the third lug on the Volume pot?  Does it mean
two wires should come off the board with one going to each lug?

Either way would work fine as both arrangements have the same electrical connection. I personally would have a single wire going to volume pot lug 3, then another wire from there to the tone pot lug 3, though the order does not matter.

Finally, when it says that lug1 of both the Tone and Volume pot go to ground, should they be grounded to the back of the pots or to the
input jack shield?  Does it even matter?

Wire them to the input or output ground: Ideally, input+output grounds, battery/power supply negative and all other grounds should all connect together on the circuit board. This is not always simple, although with Mike's layout you can make ground connections at g1 (labelled as ground) but also at b26 and e26 - Following the circuit, they are all connected. Some people just have the input+output grounds connected through the enclosure, though it's not best practice.

[shiner_man]

Wire them to the input or output ground: Ideally, input+output grounds, battery/power supply negative and all other grounds should all connect together on the circuit board. This is not always simple, although with Mike's layout you can make ground connections at g1 (labelled as ground) but also at b26 and e26 - Following the circuit, they are all connected. Some people just have the input+output grounds connected through the enclosure, though it's not best practice.

Thanks a lot.  I did the "star grounding" on my previous box and I wired all grounds to the input jack shield.  I guess I'll just wire the pots to that spot as well.

[victor nery]

Greetings,

How does a capacitor used as a treble bleed alters the taper of a linear potentiometer? I'd like to understand the theory and the math. Any input would be very appreciated.

Thanks in advance

[PRR]

> How does a capacitor used as a treble bleed alters the taper of a linear potentiometer?

Different for low or high frequency.

You can get an idea by assuming cap is "open" for low f, "short" for high f.

Past that step, you really gotta show what you are looking at. Bleed to top? Bleed to bottom? Series pot with cap on wiper? Picture worth much more than 1,000 words.

[victor nery]

Greetings,

It's this 330pF from wiper to ground in this JH-1 wah. I'd like to know how it works since it's pretty similar to the trick in guitar level potentiometers. The taper changes according to the capacitor used in a guitar level potentiometer and staring at this schematic I'm wondering if it's possible to use a 100k linear taper for sweep and fine tune it using apacitors to push the highs a little bit before it hits full toe down position. I really like the first 50% of the travel using linear potentiometers for sweep so mabe hitting the highs a little faster after this point would be perfect. 

Here's the schematic:



Thanks a lot.

[PRR]

> this 330pF from wiper to ground in this JH-1 wah.

That one is complicated. This pot adjusts a variable reactance in the tuning L-C network, inside a NFB loop. I can't work it out by hand.

However 330pFd on 100K is 12KHz, or above the guitar useful band. I wonder if it is to suppress oscillations from layout issues, no effect on "sound".