Pan-Crossfade Module

I built a Pan-Crossfader module using three J3RK FadeX PCBs as described on the Muffwiggler Crossfader Thread (will eventually be the build thread) topic.  Three PCBs provide three independent pan or crossfade units and normalizing the jacks provides the ability to pan a mono signal in four quadrants.




The J3RK PCBs are small and will work well for this module.  I made modifications to the design for the pan capability and to select the CV for either 0 to +5V or a +/-5V range.



Since the manual CV control will add to the CV input I limited the sum to a 0 to -7.5 voltage range for the OTAs.  I increased the CV In impedance to 100K so used a low current zener diode in a SMT package.  There is just enough room to scrape the solder mask off the run beneath D3 to mount the zener and move D3 to the rear of the PCB.

These modifications required cutting 6 traces on the front and 1 trace on the rear of the PCB.



Power consumption: +15V @ 48 mA, -15V @ 50 mA

Modifications to the J3RK FadeX schematics

Mouser BOM (includes modifications)


This scope image shows the pan functionality with a 0 to +5V CV control




I made a bracket out of 0.050" aluminum to stack the three PCBs.  I daisy chained the power from the back of each PCB using a short cable and a 0.100" MTA connector.   I've added a seven extra wires to the PCB for my modifications and used one pad of R36 and R37 for my extra 10K and 150K resistors so those terminate in a pad.  The other five wires solder to pin 1 of U2 & U4,  to the pad of R27 that connects to U5-2, to the cut pad of R29, and to the center of the bias trimmer.


This photo shows the first channel completed..


This photo shows the complete module assembly.




I designed a 2U panel for the three Pan-Crossfade sections.  I normalled the jacks for a four quadrant mono pan and indicate the inputs and outputs with blue legends.  A positive CV input pans to the A output so a positive X CV pans from left to right and a positive Y CV pans from B to A.  -X-Y CV pans to the lower left jack; +X-Y pans to the lower right jack; -X+Y pans to the upper left jack; +X+Y pans to the upper right jack.  visualize a cartesian orientation where negative X and Y CVs pan to the lower left jack and positive X and Y CVs pan to the upper right jack.

DJB-021 Pan-Crossfade FrontPanelExpress file