[1083] A/B Box with the Relay Bypass

Date: December 3rd, 2011 | Comments : [10] | Categories: DIY.

true bypass relay

I have added instructions to the relay bypass support page to show how to use it as an A/B box controller. Also added are instructions on using the relay board to switch the booster/buffer outputs of the AMZ Mosfet Booster.

Order the AMZ Relay Bypass.


10 Responses to “A/B Box with the Relay Bypass”

[2470] Josh Says: 12:02 pm, December 1st, 2011

How does this compare with the ones offered by Jack Deville and Cusack? I am really interested in doing it myself for the couple pedals I am currently building. Also, is there a cheaper alternative to the Carling switch that would work well? Like the soft touch switches from PedalPartsPlus?

[2471] admin Says: 1:20 pm, December 1st, 2011

I’m sure Deville and Cusack make fine products, but I don’t know anything about them except that they use a different microprocessor than my board uses.

There are lots of soft touch switches available, but I have not tried the one from PPP. I bought the last batch that I have been using from All Electronics.

regards, Jack

[2477] Chris Says: 12:49 pm, December 4th, 2011

I used an SPST I bought from West Florida Components that works very well. Haven’t tested it with the AMZ bypass board, but rather with a (probably similar) AVR switching system I designed to be integrated into my main FX boards. Mine uses the ATTiny13A instead of what looks like the ATTiny12 on the AMZ board. I’m also using a Schmitt-triggered inverter instead of doing software debouncing, since I have an excess of these inverters :), but I’m sure it’s no more bouncy that the Carling, etc. switches.

[2480] admin Says: 9:43 am, December 5th, 2011


The WFC switch looks very similar to the ones that I bought from All Electronics. They work quite well and seem to be very sturdy. I haven’t had a problem with contact bounce, and the bypass pcb uses a combination of hardware and software debounce.

My first (rack) version of the Relay Bypass used the AT90S2313 then I went to the ATtiny11 for the pedal version, switched to the ATtiny12 and now the ATtiny13A since the T11 is obsolete and the T12 seems to be on its way out with Atmel.

regards, Jack

[2532] Rick Says: 7:31 pm, December 28th, 2011

Hi Jack, thanks for the site!

I’ve got three DOD pedals that are a bit noisy and also seem to cut out a fair amount of my guitars high freqs (especially the oldest one, a FX65 chorus). I’d quite like to modify them to make them usable if possible.

Would this relay true bypass circuit be suitable for them?

Most people don’t like the little microswitches the DOD pedals have but I don’t mind them. Will they work OK with this circuit also?


[2535] admin Says: 4:14 pm, December 29th, 2011

The pedal switches on the DOD pedals should work okay with the relay bypass, but I have not tried it. I have used it on Boss pedals which have similar switches.

If there is room to fit the 1″ x 1″ pcb in the DOD pedals, it should be a good mod.

regards, Jack

[2537] Rick Says: 10:08 pm, December 29th, 2011

I should be able to fit it in, how tall is the completed pcb roughly? Around 10mm?

If worst comes to worst I could use the battery space.

I’ve been wondering if I can modify the pedals to get less noise and high frequency loss. Would replacing resistors or electrolytic caps for metal film types make an improvement here?

I’ve looked through some of your other circuits where you’ve put a smaller higher quality cap in parallel with a larger electrolytic to help smooth it out.

As you can tell I’m a novice and any advice would be very helpful!!


[2559] admin Says: 9:58 am, January 3rd, 2012

The completed pcb is about 10mm, but the adhesive pad under it will make the total about 12mm or so.

Metal film resistors are less noisy, especially in higher values. I use a lot of 1M resistors in pedals and have a supply of metal film parts for this.

regards, Jack

[3901] Samuel Says: 2:11 am, June 19th, 2013

Hello. I want to build a remote a/b switch, for my guitar pedal patching system, that has a “amp chanel change” output, that should work as a latching switch. It seems that I will be able to construct suck a remote switch box from this board. You refer to a “relay bypass support page” that I cannot find anywhere. I would lige to be shure that I can actualy use this board for my desired purpose, before I buy any of them. Can you comment on this, or provide me with a support page link?

[3907] admin Says: 5:56 am, June 21st, 2013

The support page link is sent to everyone that purchases the pcb. Not a big super-secret deal, but I like to have some extra stuff just for buyers.

The micro/pcb can be used to construct an A/B switch… so can the DPDT switch relay, which is more generic.

Best regards, Jack


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