Tube Preamp repair near Trenton NJ

Another you might consider is Rich at Signature Sound in the Syracuse area.

He does some repair/warranty work for David Belles, but believe his main expertise is tube amp and preamps. He has a web site.

Nice guy.

+1 on @bigkidz a standup guy. You also have Ben Jacoby in Brooklyn a great rep as a tech.

I'm bigkidz and we are in Boonton NJ we have a listening room there and you are welcome to come in for a listen and we can repair any audio component  PM me

I can vouch for bigkidz. He just repaired a power amp  for me. And he did a rebuild/upgrade on my Counterpoint preamp. He does top notch work.