TIP: Mini DPDT "stompswitches" for 2-battery power

[Mark Hammer]

I bought a small handful of the PC-mount mini pushbutton switches a while back to try and experiment with the actuators that Steve Daniels sells for implementing "bypass on board".  Though I still mean to get around to doing that (if only because it is a great way to stick a lot more stuff inside a 1590B), another use occurred to me the other day.

One of the nuisances of units that use a pair of 9v batteries for bipolar power is turning them on and off.   We are used to using a single stereo jack for powering up when the patch cord is inserted into the input of the pedal.  Powering up a pair of batteries means either finding and springing for those exotic DPDT-switch jacks (big, bulky, rare, expensive, but they work), or using a pair of stereo jacks and taking the risk of powering up one side before the other, or using a switch.  

The switch is the most straightforward method with the least risk and cost involved.  Unfortunately, if you use a toggle switch, you can accidentally enable it and find that the pedal which you left in working order on Friday is dead to the world on Monday.  The alternative is to use a sliding switch but machining a cast aluminum chassis for them is tricky and a headache compared to the ease of drilling a hole with your stepping bit for a toggle.  There are some electronic ways around the nuisance, such as RG Keen's solution which uses a transistor-based circuit that permits actuating both batteries by inserting.  But these simply replace the risk of dual stereo jacks with the obligation to wire up another board and find a place for it.

It occurred to me that the little PC-mount DPDT switches that Steve sells (though I got mine in Toronto without the metal stabilizing frame, and they're about the size of a modern 100uf/16v cap without the stabilizing frame) could be easily placed on a circuit board with just a small hole above the switch.  In effect, the pushbutton switch remains easily accessible, just not by accident, and would take up about as much room as a DPDT mini-toggle, with the same amount of machining.  Alternatively, one could put a pushbutton cap on them and have them protrude, like the pushbuttons on some of the newer MXR pedals (and these are the same switches used, in fact), but in a location where accidental switching would be unlikely to occur.

Just a thought.

[cd]

You can switch two batteries with a regular stereo jack with RG's circuit seen here:

http://www.geofex.com/FX_images/splitter.gif

[Mark Hammer]

Yeah, its a good idea, in fact a great idea, but its more work and also requires you to remove the plug to disable the batteries.  That's not what I'd call a "hardship", but the "submerged" pushbutton has the advantage of letting you leave all your patchcords in place.  If you use a powered pedalboard that may be moot, but if you have a bipolar-powered peda that does not permit you to use the pedalboard power, being able to depower the batteries and leave the plugs in is a nice feature.l

[cd]

An on/off power switch makes sense technically, but in practice, I'm not so sure.  If Joe Guitarist has a bunch of other effects, they likely either all work by plugging in the input jack or plugging into a wall-outlet.  So if you're unplugging all your FX anyway, one more is nothing.  If anything, having to remember to switch off the one lone dual battery effect is harder than just unplugging everything.

On the other hand, if JG has a pedalboard with a bunch of FX, he probably already has a dedicated power supply, so the battery issue is moot.  If JG doesn't have a dedicated power supply (and enjoys blowing $5 on a Duracell or 2/$1 carbon) - well, there's a GREAT first time DIY project!  I always recommend a dedicated power supply as a first time project - it's really difficult to screw up a bridge rectifier, 7809, and a bunch of caps.  And with a 9VAC wall wart, there's no worries about playing with 120VAC from the wall.