building an a/b box

[Narcosynthesis]

right, i found this schematic



thing is i would prefer to build it with led indicators to show which output is selected, how would i add these into the circuit?

and this would need a battery to be added, but i hopefully intend getting a power supply sometime soon so would like it if i could use either a supply to power the led's or a battery, does anyone know how i could add this into the circuit

and last of all, what parts would i need to get, there is a maplins where i live so i would prefer to be able to buy from there, i knw they make die cast aluminum enclosures so i would hopefully use one of them, and i know i need three jacks (opne style, mono or stereo?)
im not sure what switch i would need or what jack i need for a power supply, could anyone direct me to what i need?

much thanks

David

[Peter Snowberg]

Welcome David,

You just need to use a 3PDT switch and use the third pole to switch the LED(s).

For power, I think that standard at this point is pretty much a 2.1mm coaxial with negative in the center. For reference, I like Mouser part #163-4302, but that's one one of a zillion choices.

http://www.mouser.com/catalog/specsheets/041699.pdf

If you're using external power, I would tend to go for two LEDs of different colors, or you can use a singe 2 color LED with three leads.

Add two resistors and there you have it.

Take care,
-Peter

[Narcosynthesis]

how would you wire up the two leds, switch and power supply (preferably with the option of a battery until i can get a power supply)

David

[smoguzbenjamin]

Take the 3rd pole of a 3PDT switch and connect +9V to that, then on each trow your connect a resistor and led in series to indicate A/B. It's really simple, You gotta get the hang of it... I thought of an idea for a A/B box with a DPDT swicth though, lemme see if I can find it.

[smoguzbenjamin]

here it is:

http://scorpius.spaceports.com/~ubermaus/guitar/abbox.html

Be sure not to connect the ground signs from the LEDs to the ground lugs of the jacks. Doing that makes a hell of a noise, at least, mine did. :mrgreen:

[Fret Wire]

Here's another a/b box you can build.



http://www.fulltone.com/qaframe.html

[Narcosynthesis]

ill try it with the schematic i got, looks more complicated, so it obviously must be best   (it stops ground loops or something like that i think)

ok another question
for powering it, i connect the negative battery to ground (the black wire on my picture) then the positive to the middle lug on the switch, that will power it with a battery, if i want to use a jack, should i just wire it the same so it appears in parrallel to the battery? then just take out the battery from the pedal?

David

[smoguzbenjamin]

Hmmm, I'm not sure what you mean, but here's the way to do it.

You connect the read lead from the battery snap to the sleeve (middle) lug of the jack. Then you connect the ring lug of the jack to anyplace in the circuit that needs the +9V. Yes, it's that simple :mrgreen: I think it's also in the FAQ somewhere, but I can't remember :oops:

By the way, the most complicated schematic is not always the best! How complicated a schem is doesn't nescesarily mean that it's better. You could have a really complicated schematic that sucks, and a simple one that does the same thing a lot better!  

[DaveTV]

I also recommend checking out the Fulltone A/B box. The instructions are excellent for a first project (in fact it was the first box I built). Make sure you cross-connect the wires on the switch as shown.

The basic wiring for an A/B box should be pretty much the same in any schematic--there's really not much to improve upon. The differences will be based on the type of switch and if you want to include an LED with true bypass. 3PDT switches are fairly common these days and are perfect for building A/B boxes with LEDs.

[Ansil]

i redrew the fulltone cause people said it was to dark so if you need a color version.. go here.

www.geocities.com/cemaynard1134/help.htm

about half the way down.. it also links to the fulltone link

[ian87]

no workee, ansil. you have antoher FTP site? if not, i can UL it to mine.

email to ian AT blawg DOT com

[marc]

Hi, just curious, I've been thinking of making an a/b/y switch as well. Ansil, your redraw of the fulltone doesn't look to me like it's the same as the fulltone circuit, or am I missing something. Specifically, the LEDs don't seem to be connected to ground...So which one is the real deal? Fulltone says that thier circuit grounds the input to defeat hum, does yours as well? I think the problem is I'm just not getting it, sorry. I think i have a minor dyslexia regarding the orientation of the 9 terminals...Ugh.

[Ansil]

i wil have to see mike said it was right. i will have to look the data transfer has been exceeded

[Ansil]

all better now  the original had one wire left off of it.  from pin 2 middle row to ground.  anyway i redid it now showing resistors and the whole nine yards

[Narcosynthesis]

this is what i will build, from what you have said it should be right

on the input jack, the two on the right are the ones that are connected together when the jack is in place?

one last thing, for the wiring, would it soudn good if i just used standard school physics/electronics wire for it or should i spend a bit more cash to get some wire that i probably wont use for anything else

and any other tips to help me making the box?

David

[smoguzbenjamin]

Yup, that's how you use a stereo female plug to turn power off/on. I'm not sure about wire quality, shouldn't make that much a difference. I use wire I ripped out of an old AC cable and don't use, so I use the wire from that... My pedals sound ok!    At least the prototypes do, I haven't boxed anything in my life before I've only drilled holes in existing FX

[Transmogrifox]

Looks Excellent.  I think I'll build one myself...perhaps add a A and B function.  

For the input jack:
Plug a jack into the cable before you solder anything.  measure the resistance between the cable tip and each of the lugs.  For the one that reads zero (or .4 ohms or so), this is your signal path.  The other two connect to the ring, and whichever order you connect those two according to the schematic below will not make a difference.  If you want to be absolutely sure which two are connected to the ring, repeat the dmm trick with the ring and lugs.

Standard school physics wire is fine.  Don't concern yourself with this stuff, you'll have a worse parasitic effect from the capacitance between the wires in the box than what any wire itself would cause.  You could probably do just as well as "high quality" wire with pieces of a barbed wire fence.  

Be more concerned with how you arrange the wire.  Don't make a "rat's nest" mess, use as short of segments as you can, and don't tape any of the wires parallel to each other over a very long distance.  Also, try to separate the power supply wires as far from the signal path wires as possible.

You have a good design to work with here, with the unused jacks being connected to ground.  This also helps to reduce switch pops, as the unused line doesn't charge a coupling capacitor up to a different potential, that is then discharged into the signal path when switched on.

[Narcosynthesis]

For the input jack:
Plug a jack into the cable before you solder anything.  measure the resistance between the cable tip and each of the lugs.  For the one that reads zero (or .4 ohms or so), this is your signal path.  The other two connect to the ring, and whichever order you connect those two according to the schematic below will not make a difference.  If you want to be absolutely sure which two are connected to the ring, repeat the dmm trick with the ring and lugs.

youve lost me there. im not really sure what you are trying to say

they way i think the jack works (may be wrong) there are three tags i can solder to, one goes to the tip on the guitar lead, this is the hot (input/output) jack, there are another two tags, when the jack is in place they are both connected together via the main 'body' of the jack, so power will flow from the battery through part of the jack and into the circuit, these are also connected to ground, ie,  the same part on the other two jacks

or have i got it wrong?

David

[smoguzbenjamin]

First of all I'd like to say that when you double-post, edit one of 'em to say "double" or something cos two long posts are a pain in the ass.

That said and done, I though your explanation of the jack switching was quite confusing. You must have wierd jacks, but the resistance between the tip and sleeve/ring lugs should be infinity, meaning they're not connected. If you plug a mono jack into a stereo plug though, the sleeve and ring lugs'll have a resistance of 0 Ohms. Is that what you meant. In any case the diagram was correct, so no damage done

Not trying to be mean or anything, but I got really confused about what you meant

[Fret Wire]

Your diagram looks nicer than the original. Double check your resister's though. One is 10k, the other 2.2k. It's perfect for a 1590b box.