Metaxas Papillon PCB Layout. Easy access to trim the EQ on the REC/PB PCBs without sacrificing long wiring runs. The PCBs will also feature the ability to “Plug/Play” Gain stages. It all starts with modified Stellavox single-ended circuits, you can also swap them for DC differential circuits or even 12AX7 valve stages. What you see here is the “starting point” with Stellavox modules (same as T-RX Tourbillon).