PSC Adapter Barrel Ā• 600 OHM XFRM Ā• Professional Sound Corporation has designed and built a range of adapter barrels to meet the needs of the professional sound recordist. These ruggedly built XLR barrels provide specific audio functions that may not be found as standard features on all of your audio equipment. By utilizing these barrels, the sound recordist can solve many problems both in the field and in the studio. 600 Ohm Transformer Provides transformer isolation between equipment.