Your tube components may be colouring the sound, but that’s not the issue. And byw, the Node can’t be hooked up to drive a power amp, it has the correct voltage to be used with a preamp.
For digital coax cables, try auditioning one from a dealer that has a trial period or return policy.
I have used Cerious Technologies Graphene Extreme...
http://www.cerioustechnologies.com/#products
Also Acoustic Zen and have heard good reports about Black Cat Cables.
For digital coax cables, try auditioning one from a dealer that has a trial period or return policy.
I have used Cerious Technologies Graphene Extreme...
http://www.cerioustechnologies.com/#products
Also Acoustic Zen and have heard good reports about Black Cat Cables.

