DC Trap/Filter/Blocker for toroidal transformers

Nowadays the AC mains network is heavily polluted by various domestic appliances, industrial electrical consumers etc. This can lead to buzzy toroidal transformers (especially the power ones). Proposed DC trap (blocker, filter) will remove or at least lower the buzzing.
Schematic is similar to this one used in well known Vladimir Shushurin’s Lamm-1 amplifier. An article with in-dept explanation of how DC blockers work can be found on Rod Elliot’s site (http://sound.westhost.com/articles/xfmr-dc.htm).

ALPS Blue Velvet PCB

PCB for ALPS Blue Velvet

This is a PCB for mounting ALPS RK27112 stereo potentiometer.
PCB is with dimensions 28x32.5 mm (1.1×1.28 in.).
PCB thickness: FR4 1.55 mm. Copper thickness: 35um (1oz). Surface finish – Nickel Gold (ENIG).
It is one-layer design with solder mask coating on bottom layer for best durability. Silk screen is placed on the top of the PCB.

PCB has abilities for mounting 1 pcs. ALPS RK27112 (Blue velvet) and 2 pcs. 4-pins Molex Headers & Wire Housings (Mouser part # 538-171856-0004) for INPUT and OUTPUT connectors.