Hum gets louder when unplugged from mains

[mark2]

Building a Love Squeeze: http://effectslayouts.blogspot.com/2017/11/rothwell-love-squeeze.html

I got the pedal working but it's very loud when bypassed (like this http://beavisaudio.com/techpages/StompboxWiring/). It gets even louder if I switch from AC adapter to a battery, or unplug it altogether.

It worked fine before housing it and hooking up footswitch. Wired like this: http://beavisaudio.com/techpages/StompboxWiring/

After enclosing and adding a footswitch, only a loud hum (no signal) when powered on.  When bypassed, the signal goes through but it has a hum, about 3x louder than when the guitar is plugged directly into the amp.

Is this a clue to help track down any problems? ... I found that when unplugged from the power adapter (whether or not battery is plugged in), while bypassed, the humming gets louder.

[mark2]

By the way: I checked for continuity along the ground at many points and it was okay.

[mark2]

Update: Pedal is working. Bypass still has loud humming.

My wiring isn't actually like the link above.  Instead I have input and output sleeves connected, then output sleeve connects to the smaller version of this 3pDT board: http://effectslayouts.blogspot.com/2015/03/3pdt-footswitch-pcbs.html

[mark2]

Here's a video here in case it helps. You can see the humming gets a little quieter (but not much) when I touch the switch: https://www.youtube.com/watch?v=WMiNwy-DxKs

I took a duplicate board and switch and wired up an input and output jack. i.e. made a switched guitar cable: https://imgur.com/NQtwYGr
It has the same hum.

It's not really responsive to touching guitar strings. It IS responsive to guitar volume. Humbuckers and SC have the same hum.

[j_flanders]

I took a duplicate board and switch and wired up an input and output jack. i.e. made a switched guitar cable: https://imgur.com/NQtwYGr
It has the same hum.

Your 'switchable' guitarcable is partially unshielded: from the input jack to the switch to the output jack there's no shielding, and thus susceptible to external noise or interference.

The same thing happens inside your pedal, but when the enclosure is metal and when it's connected to the sleeves it will serve as the  shield.

When the pedal is on, the signal gets converted from high impedance to low impedance making it less susceptible to external interference.
When the pedal is in bypass, the signal stays high impedance and is more susceptible to external interence.
Which could explain why you get noise in bypass and not when on.

Do you have a good 'electrical' connection (no rust or paint) between the metal enclosure and the sleeves of the input and output jacks, which in turn are connected to the shielding of the guitar cable and the cable going from effect to amp, and eventually to mains earth?

[mark2]

Do you have a good 'electrical' connection (no rust or paint) between the metal enclosure and the sleeves of the input and output jacks

Thanks for the info about impedance. That would definitely explain the behavior I'm seeing.

And no, there's no a good connection between the enclosure and the sleeves. I tried touching a jumper between them to see if it helped, but it didn't... however it was open and I didn't sand it down so I'll try doing this properly now.

Thank you!

[mark2]

I sanded down a spot in the enclosure and soldered a wire between it and ground (and checked continuity to the input and output jack sleeves)...
Unfortunately that didn't seem to help.

I also tried a shielded wire soldered between two jacks, tip to tip, with one end of the shielding grounded to the sleeve.  An unshielded wire running between the two sleeves.  This also hummed loudly.

My only other pedal is a digitech trio+ which is very quiet, but now I'm starting to wonder if it has a built in noise gate. I'm going to try to get my hands on a couple of cheap pedals and see if they exhibit similar noise.

[mark2]

Thanks again for the help. I learned a lot... and I learned a very valuable lesson, too. 

I tried guitar->amp directly and it was quiet, but I failed to try both cables.

It seems to simply be a bad cable.

It doesn't explain why the Digitech Trio+ is quiet with the bad cable though.  I'm still eager to see how other pedals perform (and should know more in a few days).

[idy]

Possibly digitech whatever is buffered...and your problem is one of the little headaches that buffering takes care of...