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Post by flateric on Jan 23, 2009 11:40:09 GMT -5
If I used 2 DPDT switches to make an A/B X/Y box, where the first switch chose one of 2 inputs and the second switch chose 1 of 2 outputs, this should be a pretty straightforward wiring, right?
The other half of each DPDT switch could then be used to switch corresponding LED's as indicators.
Would the LED's + battery circuit need their own separate ground or could I connect to the common ground wiring from the 4 jack sockets?
(The purpose of the box woould be to allow to switch quickly between 2 guitars on stage and choose output to amp or mute the amp and go into the tuner.)
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Post by JohnH on Jan 23, 2009 16:03:50 GMT -5
Seems like it should work. My thoughts would be:
Does the switch controlling the output need a third pole, to shunt the unused output to ground, which is quieter than leaving it hanging, especially if amp is on high gain?
Power can be engaged using a stereo jack on whichever of the four sockets you think is most convenient for plugging into (assuming you might leave the box set up with most of its leads for a period between use). But maybe consider also having a separate power switch, to save battery life when you dont need the LEDs? Your switching of course, will still work without power.
As to a common ground for the signal and LED power - I think its OK, certainly no problem while playing. I wonder if the surge of power through the LEDs when switching will induce a small 'click' in the signal? I'd guess it shouldnt be much different from LEDs in a normal stompbox however.
Do you want a dc power socket as well, to run the LEDs from your stompbox supply?
John
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Post by flateric on Jan 23, 2009 18:30:33 GMT -5
I guess a 9V battery would last a good few months only powering 4 little LED's, only 2 would be on at any one time, so maybe a DC mains socket is overkill for low current drain. Can you help me understand the third pole/unused output to ground issue? Here's the rough schematic I scribbled out:  |
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Post by flateric on Jan 23, 2009 18:53:20 GMT -5
Is this what you mean?  Is there a benefit doing this to the input stage as well? |
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Post by JohnH on Jan 23, 2009 21:46:40 GMT -5
That looks like it would work - both versions. The thing about grounding the unused output, is like when you have a guitar cord plugged to the amp, but no guitar - it can pick up a bit of noise, but if you ground the tip, its dead quiet - it depends how much gain you are using.
Theres no point in grounding the unused input.
How long the battery lasts depends on the LEDs. I have some that use less than most, and run nuicely at about 2mA. Two of those might work well for about 100 hours or so with a 9V battery.
John
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Post by flateric on Jan 24, 2009 10:30:24 GMT -5
Here it is finished and all functioning correctly. Thanks to JohnH it is very quiet and no 'popping' when the channels are switched. Perfectly in time for tonights gig.  |
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Post by JohnH on Jan 24, 2009 14:10:40 GMT -5
Nice quick work! I think I want one! Its amazing how those jacks and switches fill up the box. +1 to you for presenting a useful but simple device.
John
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