Idea: Switching a Parallel Loop

Posted: June 9, 2015 in Modification, Tube Amps
Tags: , , , , , , , , , , , , , , , ,

Nchannel depletion mode Mosfet exampleI’m thinking of a way to mute the dry signal from the parallel loop in my Mesa Dual Rectifier Solo 100.  There are already a few widely distributed mods, but none keep the functionality completely intact.

The depletion mode mosfet is a closed circuit when no power is applied to the gate.  When the bias voltage appears on the gate (at the same time it opens up the jfets), the channel between source and drain will pinch off, muting the dry signal.  I’m not sure exactly how to do it, but this is an idea I’m working on.

(EDIT)  Since beginning this, I found it practically impossible to get the correct Mosfet to implement this idea as it is.


My other idea is to place a relay IC on the gate of V4b and select between the the wet and dry paths.  The red line represents power to the IC.  If it’s a “normally closed” switch, the default will be the dry path.  When the power rail to open the Jfets becomes active, it will throw the switch to the wet path.  This effectively makes dual serial paths.  The FX Send function would need to be adjusted to compensate for any volume differences, unless the effect unit has a gain control.


All the functions of the rotary switch should continue to work, since the relay LM3914, foot switch, and always on selections will always light the LED in the 4M33 to turn on the loop and close the dry path at the appropriate time.

  1. […] thought to myself, what would do that?  One thing that came to mind while off on a tangent is the idea to pinch the dry channel off.  Then the light bulb flashed and blew out from me being so dense.  It’s not only easier, […]


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