Guitar Pedal jack (phone plug jack) question - Page 1
Forum section: electronics / repair

author: Excavatoree
author_rank: Frequent Contributor
timestamp: August 03, 2016, 04:26:20 pm
content: I had a DaveCAD drawing, but it was too large to post, and I think I can describe the problem without it.I have a guitar input jack (to a distortion pedal, accepts a 1/4 inch "phone" plug - two conductors, tip and ring) that has three terminals. It's not a switched jack, as the switched jacks I've seen on Digi-key and elsewhere switch the "tip." This plug has two terminals for the ring. I can't tell if they are supposed to be connected all the time but aren't, or if they are supposed to connect when a plug is inserted, because they aren't connected then, either.The circuit used them as a "tie point." When I add a jumper, the pedal works. Without that jumper, the power connections go nowhere and nothing happens.Has anyone heard of such a connector? my first thought was to simply add a jumper, but I want to make sure I'm not ignorant of some important reason to do things that way.

author: Refrigerator
author_rank: Super Contributor
timestamp: August 03, 2016, 04:45:27 pm
content: That's a feature that all "good" pedals have.Basically it uses the ground on your audio cable to jumper across the right channel and negative of the battery to act as a switch.If you're using a stereo cable it means that the battery negative is going to your right channel but not to the ground.You can easily fix this issue by getting a mono audio cable, or a 1/4 female stereo to 1/4 male mono adaptor, or you could make the adaptor with a female jack, a bit of wire and a mono plug.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: August 03, 2016, 05:04:15 pm
content: Quote from: Refrigerator on August 03, 2016, 04:45:27 pmI'm trying to understand, but this is a mono device - two conductors in and two out using a two conductor mono cable. Are you saying a stereo jack was used and it is intended that the mono plug completes the battery connection? That makes sense. That's why I didn't see any connectors like it - I was looking for mono jacks. Seems I should replace it with another stereo jack, as the existing one is NOT making the connection. The internal contacts may be damaged or bent, or some other problem may exist. I could jumper it, but then the pedal could be left "on." (there is a separate switch, if that matters)Am I understanding you correctly?Thanks for your help.

author: Refrigerator
author_rank: Super Contributor
timestamp: August 04, 2016, 07:45:52 pm
content: Quote from: Excavatoree on August 03, 2016, 05:04:15 pmYeah, that's about right.It uses a stereo jack and since guitar only needs mono plug it uses the unused right channel so that the plug shorts it to ground thus completing the circuit.

author: Buriedcode
author_rank: Super Contributor
timestamp: August 05, 2016, 09:44:21 am
content: This is so the pedal is powered when there's a plug in the input jack. If the main footswitch was to power it up/down then there would be a delay in startup which isn't good for sudden changing of effects. The side effect is that even when bypassed, if the cable is plugged into the pedal - it'll drain the battery.Jacks are generally the first thing to go in guitar pedals, like most things, the mechanics/connectors go first as they are subject to the tresses of constant plugging/unplugging. Bypassing is either done with a large switch (DPDT or 3PDT) or with JFET's (like in DOD/digitech/boss). You can mod these to be momentary which is handy for sudden bursts of distortion or delays.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: August 05, 2016, 12:02:37 pm
content: Thanks for the info. I haven't done anything with guitars and my limited audio experience was a long time ago. I thought the mono pedals used mono jacks. I'm glad I asked about it. There's a working stereo jack there, now and it's working as designed.