How to tell if a pedal is true bypass?

[pigyboy]

Hi All,
Has anyone ever heard of checking if a pedal is wired true bypass by plugging the pedal into an amp with nothing plugged into the input of the pedal while powering it with a power supply? If it is true bypass then it will be totally silent when the switch is engaged to switch to circuit off/out?

To me this sounds crazy but has anyone else ever heard of this?

[jkokura]

I've heard things like it, but I don't buy it.

The only way to tell if a pedal is true bypass is to open it up and check the switch. The two major ways I know of to get true bypass is to use a relay, and the much more common method in DIY, the 3PDT switch. If it's switching using those methods than it's true bypass. I would rather do that than rely on the method you've described and I've heard about before.

Jacob

[maysink]

It's been my experience that a true (hardware) bypass pedal WILL pass a signal (input>pedal>output>amp) when the pedal has no power. This is due to the mechanical connections of the stomp-switch doing 2 things: connecting the tip of the input jack directly to the tip of the output jack AND shorting the PCB IN to ground.

If the bypass signal goes to the pcb AT ALL then the lack of power to the circuit will prevent the signal from reaching the pcb out and the pedal is almost certainly not true bypass.

I spent a frustrating afternoon trying to track down what I just KNEW was a bad trace on a 'fully loaded' OCD board I got over at BYOC. I saw red when my DMM screamed the PCB IN was 'connecting' to the ground of the board! Then I pulled my head out and hit the stomp-switch.... Lesson learned!

[Doc Plus]

maysink as jkokura said, a truebypass can be obtained using a relay. Depending on kind of relay, it will need to be power even in bypass mode.

[maysink]

You got an example of such a switch? I'm curious to see how that works.

[pigyboy]

Hi Maysink,
Here is such a switch:
http://www.muzique.com/schem/bypass.htm.
I bought two of Jack Ormans new true bypass retro fit pcb's
Have yet to try them but i have some cool vandal resistant momentary switches that I want to use with them.
They use a relay and a small processor. Really cool but really expensive.
$14 delivered for 2 pcb's with the microprocessors.

[Jamiroking]

uhh.... I don't get it. Isn't a 3dpt a lot easier?

[jkokura]

Yes and no.

Depends on your usage of course. Take the Octaswitch by Carl Martin as an example - True Bypass but also programable buttons (i.e. button one includes your low gain drive, phaser and delay; button two switches to high gain drive and chorus, Button three is the same as two but with a boost and the delay; Button 4 is just the chorus; etc.)

You can't do that true bypass and program thing with a 3PDT easily, but with a relay you can.

Relay's can also be cheaper (eg: small bear's price for 3PDT versus DPDT relay), and they do give you real true bypass if used correctly.

Jacob

[Jamiroking]

hmm interesting. Thanks for the info

[maysink]

Yeah. What Jamiroking said!