n00b question: does this A/B/Y box design work?

[chieljan]

Hey!
I wondered, if I wanted an A/B/Y box to switch between the 2 channels on my amp, can it be done with 2 SPDT switches? Like this:


             /--------------Tip out A
             |                  |
             0----------\       |
Tip Input----0          |       0
             0----------)-------0
                        |       0
                        |       |
                        \--Tip out B

Sleeves of the jacks are all interconnected, of course. 0's are the lugs of SPDT-switches. Guess the rest speaks for itself. I've never seen an A/B/Y done this way, so that's why I wonder if it can be done. Probably missed something that makes it impossible, but whatever:)
Thank you in advance for any replies!
Chieljan

[chieljan]

-

[chieljan]

No-one? Is it unclear or something?  A simple yes or no would do...

[Barcode80]

well, i'm not so good with ASCII schematics but from what i can tell, the arrangement you have will work. i think the reason no one does it this way is that you have no way to use indicator LEDs this way, and so you have to guess which output you are using when you first get set up. i think indicators are very important for A/B/Y boxes, since when you switch off the "Y" part, you don't know which output it is going to go to. this is fine if you aren't mid-song, but can cause some big goofs if you are trying to change the path dynamically in a song (i.e. using a talkbox for a section, or using a specific amp for just one section of a song).

[chieljan]

yeah, that's true, it's no good without an indicator. the thing here is, I wanted to keep it simple because making this ASCII was trouble enough with just SPDT switches.
My real plan is to use DPDT, using the extra lugs for indicator LEDs.

using SPDT in this kind of scheme is much clearer, would have been a mess wíth LED wiring:). Anyway, thanks barcode80! 

[Barcode80]

no prob. yeah, if you are using the indicators and DPDT, should be good.

[Seljer]

err, as far as I can see, both outputs are connected by that wire that goes to the top of the first switch, so no matter what you do, it'll always be in 'Y' mode
also, you generally want to ground to unused input so its goes silent (otherwise you get that "guitar cable not plugged in" sound)

the regular way is:
one DPDT switch for A/B, connects the signal to one jack and ground to other, and vice versa when you switch
another DPDT switch for Y, connects both the outputs together, disconnects the ground wire going to the first switch

[Barcode80]

doh, can't believe i missed that...

[chieljan]

Alright, since I'm not very good at this, I might be talking lots of nonsense now. But isn't it like, signal goes in, through switch 1, which makes it go to either both outputs OR to switch 2. In switch two, it goes to either output A OR output B. so, that should be alright, for as far as I can see...

But that won't solve the connecting of unused inputs to ground-thing, something of which I have not the slightest knowledge, but from my experience, my amp doesn't make any noise when you put in a cable but no guitar, as long as it doesn't touch anything like fingers or floor, so that should be no problem too...

Then again, I'm a noob. You guys know what you're talking about. I'll just wire it together for fun, see what happens. No better way of learning things than just trying them!

Thank you guys!

[zjokka]

I etched the pcb for the RG's active ABY box on GGG without even reading the text, but it says clearly

"Thanks to www.geofex.com for this for this A/B/Y switch with isolated outputs. Using a standard passive A/B/Y switch to switch to dual amp outputs will probably cause noticable  hum in the signal to one or both amps.  This ground isolating switch solves the hum problem.
Before you build one of these, try a passive A/B or A/B/Y switch and see if it works, sometimes the simple solution is the best."

Passive ones are here:



or here's a link to the Morley I just googled

http://www.threepoundsofbakon.com/guitarfx/buffer.htmhttp://www.threepoundsofbakon.com/guitarfx/buffer.htm

[Barcode80]

if you look over the diagram, a and b are connected no matter which position the switch is in because there is a path from a tip to b tip even when only one is switched

[chieljan]

Woops... I feel quite dumb now. Thanks for clearing my mind