Question on Pop noise I get, and proper way to shield

[caspercody]

I just got done building the GT2, using a PCB from Small Bear (which is a great PCB), and the PCB is based off of Tonepads layout (http://www.tonepad.com/getFile.asp?id=112).

I added a 3PDT switch to add in the mid band EQ



I inserted the switch between IC4b pin (7) outout and the 1K resistor (going into Q1 base).

The switch also switches the 330pf (C8 in the mid band EQ schematic), so I can keep the GT2 tone control normal when I switch off the mid band EQ.

When I first tried this, with the switch in the normal mode, the pedal sounded bad. When I switched in the mid band EQ, the pedal sounded really good, and some of the squealing with the gain turned to max went away. But why did it sound bad in the normal position.

So I connected the last switch of the 3PDT to switch on the power to the mid band EQ.

Now in both the normal, and adding the mid band EQ the pedal sounds really good.

Some questions:

When I switch the 3PDT switch to either position, I get a pop. It did not do this pop until after I connected the power to be switched? Should I put a cap across the switch terminals to get rid of pop?

In normal mode, with controls maxed it is very noisy (which reading on line is happening a lot to this DIY pedal). I am going to try to wrap shielding around some of the wiring, but my question is do you connect one end to ground? Is there a article about properly shielding wiring?

Thanks
Rob
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[caspercody]

http://imgur.com/KAxBF33

Mid band EQ image

[R.G.]

When I switch the 3PDT switch to either position, I get a pop. It did not do this pop until after I connected the power to be switched?

Your switching is causing a sudden change in the DC levels fed to Q1. This is what you hear as a pop. You need to switch only AC, not DC, to the final transistors to get rid of this. Changing the drive on Q1's base from one opamp to another will never be totally pop free, even if both are fed from the same reference voltage, because there is nearly always an offset voltage on every opamp which is not predictable, being a characteristic of that particular opamp.

Should I put a cap across the switch terminals to get rid of pop?

That will not help at all, as it does not affect the origin of the pop.

In normal mode, with controls maxed it is very noisy (which reading on line is happening a lot to this DIY pedal). I am going to try to wrap shielding around some of the wiring,

Noise normally has little to do with shielding, unless the noise is a result of RF oscillation.

but my question is do you connect one end to ground? Is there a article about properly shielding wiring?

Proper grounding of shielding is a somewhat complicated topic. The shielding won't help unless the noise is caused by RF oscillation. Even there, it's better to stop the oscillation than to shield it out. Grounding one or both ends of a shield depends on how the grounding is done in the circuit and what's on each end of the cable. It gets complicated. Basically, if reference ground is fed to both ends by other wiring, you ground only one end of a shield braid, the quiet end. If ground isn't going to both ends, the shield will carry the ground, but all return currents between the two sections are carried on the shield braid and this may cause problems too.