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Hey guys,
A friend of mine provided me with this schematic for an a/b footswitch but I'm having trouble interpreting it/thinking about how to apply this in context.
http://cathbard.com/images/temp/ABY.png
The battery is just for the LED's. The 10M resistors are for anti pop.
Any ideas on how to approach a build for this?
I think Brendan may have built an A/B footswitch so he may be able to help.
Sure when Lozza or Weirdy see the post they can supply you an easy to read diagram
Try this link has really easy a/b switch diagram
http://www.instructables.com/id/How-to-make-a-AB-box/
Hope it helps
Kimball
nice one Kimball even I think I can follow the instructions and diagram
Nicko, your schematic doesn't seem to be showing at the moment.
This one may be a little too much, but it's versatile: BYOC A/B Bypass Looper.
It can be used as just an A/B switch (using Input with Send A and Send B), or switchable FX loops with bypass, plus LED indicators.
Yo Bits this link should work for ya
http://cathbard.com/images/temp/ABY.png
Ok, schematic is showing now. It's an ABY box, so you can have either or both outputs on/off using two foot-switches. Red LED is on when output A is active, green LED when output B is active, powered by a 9v battery with optional external DC jack. The 10K resistors set the current for the LEDs (depending on the LEDs) and, as you said, the 10M's smooth out the switching. The linked arrows in the rectangles represent the two poles of the foot-switches, with the origin of the arrows being the two 'common' centre lugs on DPDT foot-switches. Is there specific info you're wanting, or just general guidance on how jam it in a box? Lawry is the real electrickery expert, but I'll help with what I can.
To build it, you'll need:
1 x stereo jack (input with power switching)
2 x mono jacks (output)
2 x DPDT foot-switches
9v battery clip
2.1mm DC jack
2 x 10M resistors
2 x 10K resistors (value depends on the LEDs you use)
1 x green LED
1 x red LED
Optional mounts/bezels for LEDs (or just super glue them in)
Hook-up wire
Some type of box, preferably metal, able to withstand enthusiastic stomping.
Nothing else is really needed as it's all just direct wiring between the jacks, switches and components.
A lot of the info in the PDF I linked in the earlier post is generally relevant and may be of use.
The main thing that was confusing me was the dpdt switches. The ones I have seen in real life have all been 3 a side but these in the schem look different.
Do I count lug 1 - 4 on the left column and 5-6 on the right column?
What do the divots mean coming out of the input/output/battery - do they indicate hot/ground?
Which type of DPDT switches do I need? on/off/on? How do you know?
If I do use a metal box how do you make a ground in it?
This is my first time reading schematics so I will be asking a few questions. I thought this would be a cool project though and I've always wanted to learn to read schems.
Cheers!
Foot-switches used in pedals are usually either DPDT (2 pole 2 position, having 2 sets of 3 lugs) or 3PDT (3 pole 2 position, having 3 sets of 3 lugs). They are On/On latching switches, that is each 'click' changes from one 'on' state to the other (as opposed to momentary switches). The 'divots' on the schematic represent the 'tip' contact on the jacks.
I'll try to draw up some stuff later today that should help to guide you through understanding the schematic and building it.
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 :) .
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
Alright.
Wiring gurus - is it possible to build this schem:
http://www.generalguitargadgets.com/...w_aby3l_sc.pdf
http://www.generalguitargadgets.com/..._aby3lg_lo.pdf
WITHOUT the LEDs/power? Make it entirely passive?
I really don't mind about the LEDs since I won't be on stage and I want to make the wiring as simple as possible.
Yep.
Use a mono jack for J1 instead of stereo (if you want), leave out the battery, DC jack, LEDs (D1-3) and resistors (R1 & R2). Still connect the black wire from J3 to SW1, but leave out the orange, red, and brown wires (and also the purple wire to D1). There should be nothing connected to the middle pole (middle vertical column lugs) on each switch, they're only for the LEDs, so you could use DPDT switches instead of the 3PDT's on the diagram.
Make sense?
Yep that makes sense. Cheers Weirdy!
If I was to make this I think I'd leave the DC power plug off. Because my 9 volt supply is + earth, I could make up a extension lead to change it to - earth but there is always the chance that it gets mixed up. 9 volts won't hurt (maybe) but still a hassle and a 9 volt battery will last a while I think.
Made one up some time ago, with out the lights and I think it would be better with the indicators.
Just my thoughts.
Rick.
Gutshot:
http://i.imgur.com/TuOxqAM.jpg?1
Wiring diagram (with notes to myself):
http://i.imgur.com/Aqxqzn3.jpg?1
The shell:
http://i.imgur.com/NhobSfk.jpg?1
Everything's done - but I'm going to leave it 'til tomorrow to test. I won't sleep if I know it's wrong. :D
I wouldn't sleep until I knew it was right.
Quote:
Originally Posted by WeirdBits
You could even try upping the value of the 10k resistors to something in the range of, say, 12k to 22k if you're using ultra bright Leds with clear encapsulations on them, I've found with some super bright Blue Leds you need a resistor value of something like 33k or so, or even 47k.
Tested today and it's all perfect. No issues at all (YAY)!
Well done Nick, nice artwork too.
Thanks mate and thanks for all your help too. The art is from a show called Adventure Time. Worth checking out if you're into cartoons :D
so stoked I finally have a clean/dirty channel
Welp
Looking at it again today I missed something when I first tinkered with it.
When I'm pressing the left switch, it's turning the clean channel off/on (A only) however the right switch is turning both on (Y).
Any ideas why the left switch isn't going between A/B?
Your right (Y) switch is working as you get both channels, and the A part of the left switch seems to be ok too, so it's probably the B switching on the left switch. Check the left-most centre lug on the left switch, as that sends the input signal to the B output.
It could also just be a dodgy switch with a bad contact, so either check it with a multimeter... or, if you're desperate, swap the left-most connections on the left switch to its unused middle pole lugs.
got the multi out and opened her up. Definitely that far left middle lug.
Will try resoldering the joints but if that fails - do I have to move the whole line across to the middle lugs or just the dodgy contact?
That left-most set of three lugs is one pole, so if a contact is bad you'll have to move the wires on each lug to the middle set of three lugs (pole).
It may just be a bad solder join, so try re-soldering those connections first before you start moving wires.
Alright I re-soldered the joint and now have continuity between the left middle lug and the mono jack tip.
Plugged it in and no luck. Just switching channel B on/off
Am I doing something stupid with the amps? Plugging into the wrong input? A/B mono jacks are for the amps right? and the far right jack is for the guitar because both chains lead to it (hot/ground)
"... switching channel B on/off" or was it channel A?
I'll post up some pics a bit later with a testing sequence for you to work through.
Ok, I've just whipped these up quickly to show which points should be hot and ground in each position (red = hot, white = ground). You'll have to click the switches to get the 'bar' contacts on the correct side for each state before testing. That's assuming you have the switches oriented correctly so that the poles (sets of three lugs) are running across the switches/images. I've numbered the lugs so we have a common frame of reference.
The 'bars' represent the active switch contacts between lugs, the little squares just show if the other lugs should be hot or ground, and the large circles show the hot and ground on the selected jacks. To test, get the switch in the matching state, then put your multimeter probe on the red 'IN' circle and the other on the red A or B circle, as appropriate. If you don't get signal then move the A/B probe to the highest number red 'bar' lugs, then next highest etc until you find where the signal stops. Repeat with the white dots.
So, for this 'A channel on' state your hot signal should be going: red circle IN -> 4-5 -> 10-11 -> red circle A. Make sense?
Attachment 1798
As it's your 'B' channel that's the problem, this is the state you'll want to check. I think you've already checked the 2-3 lugs, so it may be the 7-8 contacts. Signal path: red circle IN -> 3-2 -> 7-8 -> red circle B.
Attachment 1799
The 'Y' states ignore the A/B switch and just use the Y switch to bridge the signal across both the A and B channels, but I've drawn it up showing the 'Y' from both the 'A on' and 'B on' states just in case.
Attachment 1800
Attachment 1801
Does that help?
I am really stumped now. I followed all of the signal on every single mode and it all had continuity. Plugged in - no bueno.
Tried again - followed the whole signal chain again. Plugged in - worked perfectly.
I'm not sure if the wiring fairies have worked their magic but either way - thanks for all the help Weirdy.
I'll post up a demo when I get a chance of it in action.
hehe at least it's working.
Maybe a dodgy tip arm on the B jack not making solid contact with the plug? Give the plug a wiggle with it plugged in a see if the sound cuts out.
https://www.youtube.com/watch?v=6o0A...ature=youtu.be
and a demo is live
sorry for the wanky playing - just wanted to show the tones I'm running atm