Please help me mod my A+B Box

[mr_sooty]

Hi guys,

I'm hoping this one will be fairly straight forward, but I might be wrong.

I have this A+B Box on my pedal board. It takes one signal and sends it to two sources, with the option of having A, B, or both at the same time. I used to use it to send one signal to an amp and one to a DI when I was switching between accoustic and electric guitars in my old band. Not really an issue now. I keep it there mainly because I don't have a pedal tuner, just a standard tuner on my board, and this acts as a kill switch when I want to tune up or switch guitars or whatever.

But I have a stereo digital delay (Boss Boss DD-20), and it sounds amazing running it into two amps. You can pan the delay to bounce between the amps, or just have the same sound going to both. I'd like to eventually get a second amp, and be able to run a stereo rig. I'd like to modify the AB-Box to be able to take the two signals from the DD-20 and send them to the two amps. The box would give me the option to mute either or both amps.

The AB Box has an 'Aux in/out' jack, which seems to be good for nothing. I tried running a tuner to it and it didn't really seem to work very well. I was hoping I could turn this jack into a second instrument in. Then I'd like to split the signals, so that 'In A' went to 'Out A' via 'Switch A', and 'In B' went to 'Out B' via "Switch B'.

Possible?

Here's the box:


Here's the insides:


Then 'instrument in' jack is a little odd. It has 4 terminals, and seems to have two that resemble 'tip' connections, the springy ones that lock the jack in place. One of these looks pretty standard, the other has a little white plastic blob on it. Seems like it insulates it from the plug itself, but connects the back of it to something when the plug pushes it down, possibly turning the box 'on'. Here's a close up of that one:


I whipped up a bit of a diagram as best I could of how it was wired now. The Aux In/Out is obviously not the same kind of jack as the instrument in, so maybe I'd need to replace it? It just has two terminals. But we're only running mono signals here, it's just there's two of them.

I don't know the values of the two resistors. Also, the battery checker thing is surplus to requirements as I power the LEDs up with an adaptor via a battery clip attatchment. The power is just for the LEDs, it works without power otherwise.

I hope you can make some sense of this:


The terminal labelled '?' is the one with the plastic thingee on it.

Just a reminder, while I have learned a lot from this site, I am still no expert. I need fairly dumbed down instructions!

Cheers.

[ashcatlt]

I'm pretty well convinced you could accomplish converting this thing from an A/B/Y into a dual kill switch by removing the red wire between the two switches.

I'm not at all sure what the 4 lugs on that plug are. Based on your drawing I'd have to assume that the ? lug is a switched connection that is forced to contact the bottom lug when the plug is inserted. This saves your battery*. Leaves me stumped, though, as to where on the plug that bottom lug connects. I'm inclined to say it doesn't.

The resistor on the battery wire makes sense to me. Keeps you from burning out LEDs. The other freaks me out. You're sure that's not a capacitor?



* You'll need to be sure that if only one plug is inserted, it's always into this original instrument input!

[mr_sooty]

Oct 6, 2008 23:09:18 GMT -5 ashcatlt said:

The resistor on the battery wire makes sense to me. Keeps you from burning out LEDs. The other freaks me out. You're sure that's not a capacitor?

No, you could well be right there. Whatever it is is insulated under a black sleeve, you can actually see the sleeve in the close up shot of the instrument jack. I just guessed by the bumps that there was a resistor under there, but yeah it could well be something else.

Wow, do you really think this is gonna be that simple? So what's that Aux in/out supposed to be for do yo reckon?

There's actually two red wires between the switches, one of which I've coloured orange in the diagram. Would I need to leave the 'orange' one connected?

[ashcatlt]

I could be wrong, but i'm pretty sure it is that easy.

The Aux jack looks like it works as either an unswitched output (if connected to the input of some other device) or a second parallel input (if connected to the output of some other device) which would be "mixed" with the instrument in and that mix would then be switched as normal. I put mixed in quotes because usually a passive mixer will have resistors involved to help isolate the input devices from each other. These are not present in your drawing. Won't be an issue if you cut that red wire, because the inputs will no longer be connected.

The "orange" wire isn't exactly required to do what you're asking for, but I'd leave it. It accomplishes shorting of an output jack which is switched off. Without it, the cable becomes an antenna and could be quite noisy.

And, actually, the * above is not exactly correct either. It'll pass sound fine whichever jack you plug into, but the LEDs won't light up to indicate which amp is selected unless you plug into the instrument in.

Got a meter? I'd love it if you could confirm my suspicions on that switched jack. Plug a in a cable. Put your meter on any resistance setting you'd like. Put one probe on each lug (one at time please ) and touch the other to first the tip and then the sleeve of the remaining cable plug and report back which one reads very close to 0. If I'm correct, it'll be tip - sleeve - sleeve - neither.

While you're at it, try testing across that suspect component. If it shows some reading 0 < n < infinity, then it's likely a resistor (and we'll be able to figure its value, if necessary). If it reads open, it's a cap. If it reads 0, it's maybe a spade plug or something.

------------------
In the spirit of helping you get what you want, I initially left out my reaction to your actual proposal. I agree that it sounds like a neat idea, but I'm not sure how practical it is if you intend to be playing live.

The band on the stage will get a very strange stereo image. For example, you will likely be standing very close to one of the amps. What if the bass player is standing next to the other amp? Of course, there'll be a wall of drum noise between the two of you. What if the bassist can't hear your actual initial strums, but only the delayed signal? The poor vocalist strutting back and forth at the front of the stage won't know what time it is!

Then, everybody in the audience is going to be so far from the two amps that they are likely to get a mono wash of your fancy stereo effect anyway. Most sane house engineers run in mono so that everybody in the place gets the same basic image. Wouldn't want the folks over by the walls to be missing out on half the performance, would we?

On the other hand, if you were to have a drastically different signal coming out of each amp, that could be fun. One might be distorted while the other is clean and chorusy, or whatever. I wouldn't think of this as stereo though. More like parallel processing.

[mr_sooty]

Hmm. I can do the parralel processing option with the A+B box how it is. Actually, the delay only 'ping pong's' when on the 'pan' setting. On all the other settings it just seems to send two identical signals from the stereo outs.

My soundguy does actually sometimes run the guitar in stereo by sticking two mics on the amp anyway. As far as stage volume goes, most of the musos are using in ear monitors anyway, so I don't think it would be too much of an issue, especially if I kept the amps close together.

But it's all hypothetical anyway, because at this stage I only have one amp. But if this works, it would be easy enough to reverse anyway.

[mr_sooty]

OK, here's those measurements you wanted. I have a meter, but I really don't know what any of it means. I have it set up for resistance measurement, the setting is 2000 ohms.

The 'suspect component' eventually settles on: 046

The instument input lugs seem to react in the following way (top to bottom in diagram):

Tip
Neither
Sleeve
Neither.

So you were close!

[ashcatlt]

Well, I was looking at it weird. This actually makes more sense. Do the two "neithers" connect to each other when a plug is inserted?

No idea what to make of the resistance. The ones I have are ancient and read the same regardless of range setting. Can't use them for anything but (half-assed) continuity tests.

[mr_sooty]

Oct 8, 2008 23:42:11 GMT -5 ashcatlt said:

Do the two "neithers" connect to each other when a plug is inserted?

Umm, I don't know, it's back on my board now.

But anyway, I did the mod, and it seems to have worked perfectly well. The cool thing is that when my delay isn't set to Pan, it sends two identical sounding signals, which means that if I have the delay running into both sides of the AB box, I can still use it the same way as I used to as well. So it's all good.

Thanks for your help! I sure love this site.