Stereo Jack Trick

[cahannon]

I'm building a neutron and it talks about connecting an 'input stereo lug' to take advantage of the stereo jack trick.  If I'm not using a battery supply but a dc 9v wall wart do I need to hook up this 'input stereo lug'( I feel like the stereo jack trick is advantageous if your using batteries)?  Same question (do I need to hook it up) about the "Dual Voltage Supply Connection' rectangle on the schematic.  I'm thinking that one is a more obvious 'no' answer but I'd feel a lot better hearing confirmation from you guys.  Thanks.

[Paul Marossy]

A stereo jack can be wired in such a way that it can switch off your power supply when the pull out the cord from the jack. This is usually on the input jack. See the FAQ section here at this site, it'll show you how to do that. If you are going to only be using a DC jack, then you can just use a std. input jack. This is what I do for all of my pedals - I'm not interested in buying a bunch of 9V batteries all the time.

I'm not sure I understand the second part of your question...

[Mark Hammer]

RG has a document/circuit posted over at GEOFEX which uses a *single* stereo jack (the "jack trick") to enable/disable a pair of batteries. for a bipolar supply.  

One of the problems that bipolar supplies create is that you need to find a way to turn on both batteries, and generally within a short period of each other (i.e., having only the negative but not the positive supply running for a while may not be all that beneficial to some semiconductors).  One solution is to use a DPDT slide or toggle switch to do it, but then you run into the inevitable situation where the pedal gets jostled in transit, and you arrive at a gig just in time to find out that the battery switch was in the "on" position for tha last 4hrs during the drive to the gig.  Not good.

Obviously, the "jack trick" is an elegant solution because: a) you need to stick a jack in there anyways, b) you don't have to buy, and install a switch, and c) once you pull the plug out of the jack, the battery cannot be accidentally connected.  If you try and do the "jack trick" with conventional stereo jacks, you have to have two of them and should try to insert plugs close together in time (and if you pull only one out, out of force of habit, you may have a problem).  You CAN buy some of those fancy multi-contact phone jacks that allow an inserted plug to move a bunch of secondary contacts around and simultaneously connect a pair of batteries (incidentally, these can often be found as headphone jacks on those old 8-track and cassette decks you see lyingby the curb on garbage day), but they are often expensive and hard to find.

RG has provided apurely electronic solution that permits use of a single stereo jack to do what you'd normally need a switch or pair of stereo jacks to do.  It was inspired partly because the Neutron/Mutron requires a bipolar supply and sometimes a 7660 unipolar-to-bipolar circuit doesn't supply enough juice from one battery.  

He's a clever lad, that one.  I think we should promote him.

[smoguzbenjamin]

What if you use a pedalboard. I don't feel like jacking all my pedals in and out all the time (pardon the pun). I just leave the dc jack in there which shuts off any battery I might have absent-mindedly left in a pedal.