A/B/A+B Switch

[Red Phoenix]

i have found an other wiring diagram WITH relays



but i query whether if there are no noises while chanalswitching with relays

[Gilles C]

Ok, so finally, it's a A/B Looper box that you need.

For instant access to the choices, you really some electronics in there. But it's not an easy project to wire. The electronics has to do the dancing that you don't want to do 

I would suggest a PIC based control with relays for the easiest to wire box. But then, I don't think it would be a beginner project.

Gilles

[Gilles C]

So what you need is this box

http://www.lehle.com/products/D_Loop/index.php?country=us&lang=en

Gilles

[Seljer]

That circuit is basically the same thing I'm doing but in a more mechanical way. It should work fine to what I know about relays. If you're crafty you can keep the relay electronics completely sepereated from the guitar stuff and it would be real true bypass (as if you were using a regular mechanical switch).

The circuit there uses latching relays, which basically have 2 coils, one to open it and one to close it. And when your not switching the state of it you don't need to run any power through it as it stays at whatever it was last set to. You have 2 relays there and you can create whatever state by changing the position of each of them (eg: for loop A tell A to turn on and B to turn off, for loop B tell A to turn off and B to turn on.....).
The diodes are there to make sure everything flows in the right direction when you press one of the switches.

My one uses SR flip flops to determine which one to switch on/off. A flip flop is an electronic circuit that is basically 1 bit of memory (it remembers either 1 or 0). There are various classes of flipflops, an SR flip flop has 2 inputs: set and reset. If for a moment there is a voltage on set than Q becomes 1, if for a moment there is a voltage on reset then Q becomes 0. When their no voltage neither on set or reset then Q stays at whatever state it was last set to.
However this and doesn't do any actual switching so you need to add another system to do that. Either with regular relays or an electronic switch.

I made this layout for the flipflop part of the thing (mainly made it seperate because you could use it for other things too, like to control an A/B box to choose between amps):



then you run the Out A and Out B from that to control whatever switching system you're using.
If you want to use regular relays and get a full mechanical bypass then I found this article on google: http://www1.jaycar.com.au/images_uploaded/relaydrv.pdf and this too http://www.geofex.com/Article_Folders/relays/relays_for_switching_audio_signa.htm .
You'd basically use 2 DPDT relays as regular bypass switches. The only slight annyoance is that most relays you can get run on either 5v or 12v and not on the 9V our guitar effect world is based on (well they're not as common). And relays use quite a bit of power, but hey, you get full out true bypass (if you're a purist and want that)


Among the other options would be the CMOS based bypass system like described in this article http://www.geofex.com/Article_Folders/cd4053/cd4053.htm
Heres a PCB layout somebody allready made for it http://www.diystompboxes.com/smfforum/index.php?topic=40193.0 but just for the hell of it I created my own one

not as nice compared to the other one regarding the offboard wiring connections but theres less long curved runs around the board (easier to build on perfboard).
You'd just make 2 of these and run the output of the first one directly into the in of the second one. Have the 2 outputs from the board with the flipflop connected to the "Control" on each one of them.


note: both of those layouts haven't been build but I think I payed enough attention to not mess anything up  

edit: I think what you you want with just the 3 switches may be possible with just logic ICs, like a bunch of AND gates or something

[Red Phoenix]

thank you very much...

on page one you have drawn a control wiring diagram.....how can i fit the bypass with that togehter?
over "+9V" it is said "to bypass circuit". and in the bypass are "IN", "OUT", "SEND" and "RETURN".

[Seljer]

the "OUT" from the controller circuit is connected to the "CONTROL" on the bypass circuit (and there are 2 OUTs so you need 2 controllers to connect them to....)

The section on the right on the diagram on page one is only there to add LEDs, its basically connected in parallel to the bypass circuit: the wire from "OUT" on the controller goes both to the the CONTROL on the bypass and also to the side of the 10k resistor on the LED section (or I just built the LED section directly on the controller board in the layout on this page so you only have a wire that goes the the bypass circuit in the end)

[Red Phoenix]

 i understand more and more

but there are still some questions

onpage one there are two things with "D","S" "R","Q", and a Q with a line. are these two things "IC4013"

[Seljer]

Yep, that'd be the 2 sections of the 4013 http://www.fairchildsemi.com/ds/CD/CD4013BC.pdf

though you can use any SR flipflop for it (the D and |> don't matter in this case, the 4013 is an IC that can operate in different ways): http://www.shef.ac.uk/physics/teaching/phy107/srff.html (description how they work and how to make one out of NAND or NOR logic gates)
or even make it out of regular transistors: http://www.play-hookey.com/digital/experiments/rtl_bistable_nor.html

[Red Phoenix]

wich switch should i buy?
http://www.musikding.de/index.php?cPath=33_43
all 4 switch the same or different?

[Seljer]

the momentary 1PDT one

[Red Phoenix]

why momentary? or do i understand something wrong?

"1PDT"
or
"TASTER 1PDT"

Taster means...only when you hold your foot on the switch loop a or b or a+b is activ.
As soon as you take your foot away from the switch it is off.

what do you mean with "momentary"?

[Seljer]

Yeah, taster, just like you described it (the website there is in english for me)

[Red Phoenix]

but what's the reason of using momentary switches instead of normal switches.
are the IC's the reason. They have 3 switches inside. Do they only need an impulse from an momentary?
or does it have other reasons?

[Seljer]

The only need a short impulse, when they get just asignal to either the "set" or "reset" input depending on what you want) the ICs then stay in the state as long as there are no other signals on set or reset (which are tied to ground through the 10kohm resistors for when not being switched).

Heres a little table of how the flipflop works. Set and reset are the 2 inputs, Q is the output

Set	Reset	Q	Q with the line
0	0	Q stays at whatever it was last set to	is the opposite of Q
1	0	becomes 1	becomes 0
0	1	becomes 0	becomes 1
1	1	becomes 1	is also 1, this is a slightly wierd state of operation, but you end up turning off one of the inputs first, so the one that is turned off last will define of Q in the end

the Q with the line doesn't matter in our case as we're not using it.

So to get our 4 states of operation
only A turned on: tell A to turn on and B to turn off
only B turned on: tell A to turn off and B to turn on
both of them turned on: tell A to turn on and B to turn on
both of them turned off: tell A to turn off and B to turn off

and if you follower the wires from the switches, you can see for example, that the A switch is linked to the "Set" of the first one and the "Reset" of the second one and similiar for the other switches.

[Red Phoenix]

thank you very much for your help.
as soon as i have the materials i start soldering.

[tocs100]

I recently heard someone say these Morley ABY boxes bleed. If true, can someoe point out an easy fix? 
http://www.morleypedals.com/abyes.pdf

[calpolyengineer]

I don't know that they bleed, but the Morley isn't buffered so the signal can get reduced a lot. And if there is a bleed problem, a simple audio isolation transformer would fix that right up.

-Joe

[Red Phoenix]

tomorrow i will have the materials.
but i have still a question.
how do i know that i put the ic's not up side down?
i can instal the ic in two ways.....because you can rotate it in a one-eighty.
what is the right position?

bad english ..i know

[Seljer]

You see that little dot on the diagrams? that indicates pin #1. Most of the time they also have such a dot on the actual IC, or a little indent at the top side of it:
not the best image but you get the idea

Code Select Expand

  ______
1-| \/ |-8
2-|    |-7
3-|    |-6
4-|____|-5


[Red Phoenix]

and where is pin1 placed in the wiring diagram?