A passive high performance coupling volume controller designed for post processing and sound test of recording;

Homemade AT-23P coupling atennuatuion transformer and German high sensetivity permalloy iron core 6N winded by single crystal copper wires;

Homemade 6N grounding selector with 23 choices;

Protective shock-proof graphite feet;

CARDAS-RCA/NEUTRI XLR

The case with different multi-layer metals and different coating materials can protect it from interferance.