A/B Box Suggestion

[Baran Ismen]

Hi all.

I have intentions to go into full analog in time, and I plan to make myself some preamp pedals both for clean & saturation channels. For clean, I don't have anything yet in my mind, but for dirty, I'll go with a Dr. Boogie first as I like the pure raw, heavy, relentless Dual Rec sound.

Anyhow, I have this question in my mind. Is there any possibility for me to make a switchbox that, I'll go into that my clean & dirty preamps "separately" into it, and with a 3pdt switch, I'll split the chain as clean or grit and send with a single output to following effects, so both will be on but with the hit of a switch, I'll activate the one I want.

In theory, it seems doable, and yes, in this case, I'll completely be eliminating the real amplifier, but as I don't own any and am bound to use the ones that the stage we're playing live offers -and they're usually crappy & overly-used as one can guess-, I'll be using the clean channel at noon position of everything and set the rest from the pedalboard. That's how I use my GT-10 processor right now. I know 4-cable method should be used but that's a bit complicated so..

Anyhow, anyone can help with a basic schematic for above-mentioned matter would be most appreciated!

[GibsonGM]

It seems as though you're asking for an A/B to send your signal down one or another path, and then you'll need a mixer where the paths converge and head either to more FX or to the amp.

AMZ has a really nice, easy to make JFET-based A/B circuit.  Opamp mixer schematics are all over the place if you search, even in design notes in their data sheets.  And by looking, you'll probably find this has been done, documented, with a full schematic of both parts ready to go 

[Baran Ismen]

It seems as though you're asking for an A/B to send your signal down one or another path, and then you'll need a mixer where the paths converge and head either to more FX or to the amp.

AMZ has a really nice, easy to make JFET-based A/B circuit.  Opamp mixer schematics are all over the place if you search, even in design notes in their data sheets.  And by looking, you'll probably find this has been done, documented, with a full schematic of both parts ready to go 

Actually case is like this. A/B box shall let me go between clean & grit channels just like a real amp..

                                      Preamp Clean ->
Guitar -> Whammy ->                                A/B Box -> Chorus-Delay-blablabla-----> Amp
                                      Preamp Grit   ->

Oh wait, I'll also need a 2nd splitter after the whammy and/or any OD booster for this scenario.. Bollocks!

Actually, the Mooer's 011 Preamp pedal, which is an emulation of Dual Rec, has a built-in clean & dirt channel and you can do the thing I mention above singlehandedly, but I don't know about its quality, even though I use the pitch shifter pedal of them and it's actually pretty good.

I think this is what I need.

https://skymusic.com.au/products/epiphone-a-b-pedal

On a second notice, i think that such aby pedals should work bilateral as theres no opamp or transistor or something, right? So it shall work as either 2 input to 1 output or vice versa.

[GibsonGM]

Let me think on this one...a splitter/blend sort of circuit, but might need a big 'blend' pot to isolate the signals better...

Only mechanical ABY's would work 'bilateral'...many have buffers inside them that are unipolar...

I'm trying to come up with an easy way to do what you want - several ideas come to mind but require some complex switching.  Might be as simple as switching between the 2 paths and blending w/resistors!

[Ben N]

As ready-made solutions go, a Boss LS-2 is a lot cheaper than the Epiphone pedal, and will handle your routing requirement just fine.
Mike's DIY suggestions are all good, but for your needs I would do the front end of the Splitter blend (does the same job as the AMZ circuit, but without annoying JFETs that you have to select and bias individually and you may only be able to get in SMD versions nowadays), and ditch the whole return circuitry, substituting a simple on-on SPDT switch (DPDT if you want LEDs). No need to switch the inputs if you have the splitter buffering the signal path into the preamps.
That's all assuming you just want to switch between the preamps. Of course if you want to be able to blend between them, use the whole Splitter-Blend circuit, which not only mixes the outputs but also lets you reverse polarity on one loop if you need that.
BTW, the Boss pedal can also do mixing, but it doesn't have a polarity switch. (Come to think of it, that would make a cool mod, if anyone could find the schematic and somewhere to fit the switch.)

[Baran Ismen]

I actually have no intentions for blending them two, as mentioned it'll be like a regular amp switch and going between clean and dirty channel.

[GibsonGM]

Ben suggests the 1st part of the splitter/blend in order to send your signal down either the A or B path - it's capable of 'doing both at the same time' with no ill effects. Then you'd switch the OUTPUT portion of the splitter to select which path you want the signal to take.   The JFETs in the AMZ circuit will do the same thing...such high input impedance that there isn't audible loading if both are taking signal, so allows one to switch between paths if they want to.

I think this could be solved with a simple stomp switch (4PDT?).  But Ben is correct...looks like you can find that LS-2 for say $75 on Fleabay, if you'd rather not have to mess around with switching problems (I think switching sucks, TBH).  This is a 'looper' situation, really; that's another thing to look into (easy looper circuits, if you want to build).   If you want to buy, LS-2 seems good but you still have some tailoring to do withing he loop.

BTW, there is no biasing the JFETs in the AMZ circuit, it tends to be fine right out of the box (mine was with 2N5457s), but that's beside the point.

[Ben N]

BTW, there is no biasing the JFETs in the AMZ circuit, it tends to be fine right out of the box (mine was with 2N5457s), but that's beside the point.

Right, since there's no gain. That was my trauma from dealing with thru-hole JFETs (of ever lower consistency & quality & ever higher price) in other projects bleeding through, my bad. :-)

[GibsonGM]

You're a braver man than I, I stay away from SMD!  Was lucky enough to get a bunch of 5457's long ago, hopefully they'll still be around when I run out! 

[GGBB]

                                      Preamp Clean ->
Guitar -> Whammy ->                                A/B Box -> Chorus-Delay-blablabla-----> Amp
                                      Preamp Grit   ->

I'm not clear about the others things you mention, but the above is really just a loop selector (not A/B/Y). Your signal is always

Guitar -> Whammy-> Loop Selector -> Chorus-Delay-blablabla -> Amp

and the loop selector toggles between clean and grit preamps. No need for splitters/blenders.



You could do this with 3PDT but either it won't be able to ground the preamp input or it won't give you an LED (if you don't want either the 2PDT can be used).

[GibsonGM]

I think this could be solved with a simple stomp switch (4PDT?)...(I think switching sucks, TBH).  This is a 'looper' situation, really

Looks like the way to go, Gord!  Good on you for finding the looper that will work - I think switching sucks.     

[GGBB]

Not an endorsement, and no idea about quality, but I don't think I could even buy the parts for this price:

https://www.aliexpress.com/item/32347965005.html

I've seen the same ones on Amazon as well (different colours floating around). Ebay also.

If you want to spend a little more you can get the holy grail of A/B loop selectors  :

https://www.aliexpress.com/item/32987130626.html

There are of course name brand options out there including JHS and custom builders

[GibsonGM]

Don't think that price can be beat.  That's what I'd get (the fancy one).  Just my opinion, I'm not a big 'multi-path' player.

[ElectricDruid]

If you want to spend a little more you can get the holy grail of A/B loop selectors  :

https://www.aliexpress.com/item/32987130626.html

Lol, that's fantastic! "It must be good, it's got a horse on it"!

[Ben N]

Lol, that's fantastic! "It must be good, it's got a horse on it"!

Definitely worth the extra couple of bucks for the centaur.
Seriously, even if you gut it, you have an enclosure, jacks & a switch.