Washburn "Bad Dog" Phaser - volume boost problem ???

[ProToneThinline]

I picked this up several month ago at a close-out for $14.  It's not a poorly built pedal - real jacks and pots, mounted with real nuts & washers, metal case, etc.  It doesn't sound bad, except for one problem.  You get a huge volume boost when you switch the effect on.  Actually almost as much boost as my LPB-2 clone up about half-way.

I seem to remember one of the Dano mini pedals having a similar problem.  Any ideas for a reasonably simple mod to fix this?   I like the sound of this pedal, but the boost makes it un-useable.