[sdiy] idea for "almost true bypass"

[Don Tillman]

   > From: jhaible at debitel.net
   > Date: Thu, 05 Sep 2002 15:42:22 +0000 (UTC)
   > 
   > 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.
   > 
   > 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?

Hi JH!

That's a very clever solution.  I haven't heard of it being used
anywhere before, but it should work well.

(I thought that if this is a battery-powered device, it would be best
to just use a CMOS switch wired directly to the battery and ignore the
tiny current draw.  But still, the battery could die, or if the device
is AC-powered it could get unplugged, and it's certainly a good thing
to have the machine fail in the most graceful way possible.)

  -- Don

-- 
Don Tillman
Palo Alto, California, USA
don at till.com
http://www.till.com