Summoning Wiring Gurus (weirdy pls)

Nick - maybe look here?
http://www.learningaboutelectronics....tch-wiring.php - I know you are looking at a footswitch, but this should explain what the diagram is and linkage to pins on a DPDT footswitch.

I have built a straight A/B box - http://www.buildyourownguitar.com.au...ead.php?t=2481 pretty straightforward and I put links to the diagram. Will differ as it's an A/B - not A/B/Y - that's the next project. Also has the advantage of requiring an output cable to turn on - so no drain on the batteries :) .

BTW - keen to see how this turns out - have been thinking of making an AB/Y box to run a stompbox and a bass at the same time - get rid of those pesky drummers totally :).

Cheers for that DPDT link Brendan - very helpful in understanding the internals.

I'm building this one to swap between a clean amp and a dirty amp. My favourite dirt tone (my Jim Root Terror) is unfortunately a single channel amp. Currently on the hunt for a cheap class A combo to use as a clean channel.

@Weirdy I really appreciate it if you do get time. That would be extremely helpful.

So much love for this community.

If you are just switching between two amps, you shouldn't need the "Y" - the "Y" is to run both at the same time - for a first build, to keep it simple you could just go for the A/B.

As promised, some diagrams...

The upper switch shown on the schematic allows output A to be turned on/off, using a DPDT switch. It's drawn in the 'on' position which connects the input to output A and turns on the red LED. Here's the schematic's switch representation in both the on and off positions side by side with a DPDT foot-switch showing which contacts are active (the green lines). You should be able to relate this contact sequence to some of the later diagrams to follow the circuit path. The centre lugs on the foot-switch are the 'commons' that are always in the circuit, one for each pole, and are shown on the schematic as the starting/fixed point of the arrows.

Attachment 924

I didn't actually have a DPDT foot-switch spare so the above is a 3PDT photoshop'd to remove one pole (one vertical set of three lugs). The later diagrams are drawn with 3PDT switches but will just not use the middle pole (the middle vertical set of three lugs).

Jacks...

For a stomp box you usually want a way to run it from either a battery or external DC power, and ensure the battery doesn't get drained when you're not using it. A switched DC jack takes care of the former and a stereo input jack the latter. Basically, the DC jack is a standard centre negative (tip) connection that disconnects the battery when a plug is inserted, and the input jack is stereo and uses the ring and sleeve contacts to only complete the circuit's ground when a mono guitar plug is inserted. Pretty standard for a pedal, and that's the only change I've made.

Basic jack layouts: switched DC jack, stereo jack, mono jack (respectively).

Attachment 925

(I've just noticed the Switchcraft mono jacks I have used in the wiring diagrams below have the tip and sleeve on the opposite sides to the one shown above. But, you can still see which is which)

Implementing your schematic...

As I said above, the only thing I've modified is the stereo input jack and related power connections. Everything else should be the same as the schematic, I hope, with a practical implementation of the wiring.

It can get a bit confusing with everything jammed in, so here is just the labelled components without the wiring (viewed from the underside of the stomp box). Like I said, I've used 3PDT switches but I'm only using 2 poles and treating them like they're DPDT's. I placed and spaced the components to show how they connect, but you can vary the position as you want (and to suit your enclosure).

Attachment 926

(I suspect the 10K resistors will make the LEDs way too dim, so you may need to go to smaller values. Need to test)

And, here's the layout with the wiring and solder points in place. I've tried to keep it as clear as possible with the different colours and wire paths. Hopefully it's at least partially comprehensible.

Attachment 927

To make it a little easier to relate the above layout back to the schematic, I've drawn the wiring colours onto the schematic as an overlay so you can see which wires are forming which links. The ground icons on the schematic (dashed arrowheads) are the connections to the 'sleeve' lug on the stereo input jack, except for the 9V ground which goes to the jack's 'ring' lug instead. Make sense?

Attachment 933

I think it's correct, but if anyone spots any mistakes please feel free to point out my incompetence. Nick, hopefully this will set you on the right path, let me know if you have any questions or need anything more.

Also, as Brendan says, if you're just wanting to switch between A or B, but not both, then this circuit may not be ideal. With this circuit you'll need to turn 'off' one and turn 'on' the other with the separate switches for each change-over, which you could do with just a single switch on a plain A/B circuit. But, if you do want the Y option to have both A and B on at the same time, this will be fine. As an alternative, it wouldn't be too difficult to modify this circuit to have one switch select between A and B and have the other switch turn Y on/off.

Weirdy comes through again! If you get your LEDs from someone like Altronics, they should be able to line you up with the right resistors for the LEDs. From what I've used (all of three LEDs, so take this with a grain of salt), the resistance for the LEDs can differ depending on colour.

I've edited my previous post to add an extra diagram that overlays the layout's wiring colours onto the schematic, so you can see which wires form which links.

Also, I just did a quick resistor test with some red LEDs and the 10K was actually much brighter than I expected, should easily be bright enough for most pedals. The camera has distorted the actual colours a bit in this image, but it gives a good indication of the relative brightness/intensity. Left to right the resistor values are: 10K, 4.7K and 1K (on a 9V supply). There's room to go even brighter with these LEDs, but this was enough for the demo. So, I was wrong, your schematic's 10K values should work nicely for low intensity indicators.

Attachment 936

Weirdy thank you so much for that detailed explanation. That wiring diagram coupled with the schem was extremely helpful for understanding the connections.

I didn't realise that you'd have to switch amps as you have said above ^. I thought the left switch would be to switch between a/b and the right switch would be for the addition of amp Y (whether it's A or B) into the signal.

What sort of modification would be necessary to modify it like you've said above? What's the thought process behind it too?

EDIT:

Actually you know what. After some thought maybe an A/B would be the best option for me. I've been thinking about it today and outside of recording I can't really see myself blending the two amps anyway...

This thread is a perfect resource for an A/B/Y box though for sure.

Basically, the modification would be to move the A/B switching onto a single switch, with A on the left pole, B on the middle pole and the LEDs on the right pole. Then, use the other switch to link the two outputs (regardless of which is active on A/B switch), thus giving you the Y option.

But, rather than modify your circuit...

General Guitar Gadgets A/B/Y box (A or B switch plus A & B switch)
Schematic
Wiring layout

Just ordered parts for that build Weirdy. Less than $20!

Will restart this thread when the parts arrive from China (t-22 days). The price of cheapness ;)

Parts have been arriving over the past few days. Got a wicked idea for the paint job on it. It'll be hand painted.

Hint: beep boop