Besides replacing AC outlets with Maestro and now
Furutech GTX-D R, High Fidelity MC-0.5 and SR BLACK fuses, I find covering unused RCA and XLR connectors yields a nice improvement. Most noticeable is reduce HF glare and harshness ... quieter overall.
I use both Cardas and AQ caps. AQ is less expensive and I don't hear a difference.
I use both Cardas and AQ caps. AQ is less expensive and I don't hear a difference.