[sdiy] idea for "almost true bypass"

[Scott Gravenhorst]

I take it that this is one of those rare situations (biased full on)
that an FET can conduct a signal through D-S and you don't get distortion?

This is very clever.

jhaible at debitel.net wrote:
>As we all know, one can make true bypass for an FX box with a 2p2t switch, which
>routes the signal completely around the device when in "off" position.
>
>The same is possible with a relay with 2p2t contacts. I often do it that way, because
>you can control the relay with a flip flop from a momentary contact, and because
>the relay will automatically go to bypass at power-off.
>
>Now if I don't want to use a relay, I could use FET switching. This is often done in 
>Guitar stomp boxes with "electronic" switching. But this also means that the switch
>won't work properly when the power is switched off. (In stomp boxes, they often use
>switching on the output only, anyway.)
>
>What about this idea: Build a 2p2t switch from 2 JFETs and two MOSFETs,
>with the JFETs forming the bypass path. Then, when the power for the FX
>box is off, the JFETs will conduct (Gate floating, or connected with high impedance
>to S or D) and the MOSFETs will be off.
>
>Not true bypass, but the few hundred ohms might not hurt.
>
>Does this work? Has anybody used it yet?
>
>JH.

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