AB +Y switched

rocklander · Post by **rocklander** » 12 Jul 2009, 09:40

I did a bit of a search, but not entirely sure what to search for.. so I'll post it and expect the reprimand

2 questions..

I have a friend with a 2 channel amp and no foot pedal. asked me to make an ABY pedal.
he wants to be able to select A-or-B-or-BOTH.

1. will I need some sort of buffer or something in an ABY, or is straight passive switching going to work okay?

2. the ABY seemed simple enough - 3pdt to toggle the channels, and another to toggle the other 3pdt/both channels.
what I was hoping to do was have a single LED above each loop and have the 2X 3pdt light up as selected... I got stuck.. I can't see how to segregate the earth on the 2X LEDs when the 'double channel' is selected.. am I a complete doofus, or is the only way to achieve this with a 4pdt?
here's as much as I got.. thanks in advance.

rocklander · Post by **rocklander** » 12 Jul 2009, 20:08

bump? anyone?

rocklander · Post by **rocklander** » 13 Jul 2009, 20:30

Dinosaur · Post by **Dinosaur** » 14 Jul 2009, 03:41

Would it be better to use a separate LED for Y mode. That way you still have an indication of which channel will be selected when you kick it back into A/B mode.

rocklander · Post by **rocklander** » 14 Jul 2009, 03:59

Dinosaur wrote:Would it be better to use a separate LED for Y mode. That way you still have an indication of which channel will be selected when you kick it back into A/B mode.

thanks for the response. I could do that, but wanted the LEDs to physically be above the output jacks, so that when Y was selected both would light up.. I could always add an extra above each output and have 4 in total I guess..

am also keen to know if I will need some kinda buffer or something?

JiM · Post by **JiM** » 14 Jul 2009, 11:21

You can use the remaining pole of the "both" switch to tie the cathodes of the LEDs together. They will both light up, no matter which one is connected to ground by the "A/B" switch.

And don't forget to add a series resistor for each LED !
Just another idea : if you use two LEDs per channel, go for bicolor LEDs : you get orange whith red + green.

rocklander · Post by **rocklander** » 14 Jul 2009, 20:09

JiM wrote: And don't forget to add a series resistor for each LED !
Just another idea : if you use two LEDs per channel, go for bicolor LEDs : you get orange whith red + green.

yeah, sorry I thought the resistor was a given, but good point

good call re the dual colour LED!

I'm not sure I understand what you mean by

JiM wrote:You can use the remaining pole of the "both" switch to tie the cathodes of the LEDs together. They will both light up, no matter which one is connected to ground by the "A/B" switch.

any chance you could draw it for this n00b?

JiM · Post by **JiM** » 14 Jul 2009, 23:09

rocklander wrote:I'm not sure I understand what you mean by
JiM wrote:You can use the remaining pole of the "both" switch to tie the cathodes of the LEDs together. They will both light up, no matter which one is connected to ground by the "A/B" switch.
any chance you could draw it for this n00b?

Here it is. You can't miss the new wires, they're pink !
When the first switch is in "both" position, the LEDs are connected together. As one of these (A or B, we don't care) is also connected to ground through the A/B switch, the current will flow in both LEDs.

rocklander · Post by **rocklander** » 15 Jul 2009, 00:08

of course!! thanks so much.. sweet as.. I'll go that way then. thanks a bunch..

schtaf · Post by **schtaf** » 15 Jul 2009, 16:04

Morley makes an aby pedal and its schematic is published on their website. You can achieve these results with only dpdt switches. Hope this helps.

rocklander · Post by **rocklander** » 15 Jul 2009, 20:09

schtaf wrote:Morley makes an aby pedal and its schematic is published on their website. You can achieve these results with only dpdt switches. Hope this helps.

hmm.. I wondered about switching the +ve instead.. all good thanks though, I'll use JiM's suggestion since I already have the 3pdts coming

rocklander · Post by **rocklander** » 23 Jul 2009, 00:52

built and tested and failed, but fixed. I realised that if I'm to have the 'unused' signal path going to earth, AND the option of a 'Y" then when Y is in use all signals will end up at dirt (see switch 2).

removed that earth and all is good now, but there is some audible leakage between the channels unfortunately..

Haze · Post by **Haze** » 05 Jan 2011, 23:34

Hey, sorry to revive this old thread but maybe someone can tell me how I could apply this wiring into a clone of this : http://www.effectsdatabase.com/model/morley/aby/mix

Its basically an ABY with volume pots for A and B.

Thanks.