m-db,
That's very kind of you to mention, but I took absolutely no offense.
For the record, there are a couple fine points Re. NC400 assembly. On at least six occasions, clients hired me to re-wire the same subtle assembly error for NC400 built by persons not me. The symptom of this error is NC400 works perfectly fine in one system, then moved to another system NC400 mutes, playing no music.
Again, please allow me to repeat this performance advice for all applications w/unbalanced source > NC400. Any use of unbalanced IC unnecessarily and audibly degrades performance of this fine amplifier. Instead, follow this IC method:
Unbalanced source > Quasi-Balanced IC (RCA/balanced cable/XLR) > NC400 XLR, or close second choice...
Unbalanced source > RCA/XLR adapter > balanced IC > NC400 XLR
The worst application, w/the greatest magnitude of AC mains noise, is the following:
Unbalanced source > RCA IC > NC400 w/RCA input and "earthed" chassis