"My setup is Audirvana Plus 2.6.4 on my iMac to the iFI Micro iUSB 3.0, Invite 1.0 to the Eddie Current Zana Deux pre-amp out into the Apex Hifi Sangaku..." -  why didn't you use Sangaku straight from the source? or the Sangaku doesn't have enough gain? thnx

Correction on "Invite", it was meant to be Invicta (thx to autocorrect). The reason being I wanted to switch my headphones back 'n forth between the ZD & Sangaku quickly. I didn't want to move the RCA cables between the ZD and the Sangaku as it was slower.