Manufacturers with Excellent customer service

Yeah, Mike Sanders.   Once upon a time, I lived maybe ten minutes away from the guy.  I had Numbers 031 and 032 Mono Amps (or was it Nos. 032 and 033?). It was the time when he was using 8417 output tubes which were, how shall I say it, lovely sounding but a bit cranky.  He was ever patient with me as I'd show up to get replacement pairs.  As for the sound of the amps themselves, sheer bliss.

Someone else mentioned Carl Marchisotto of Nola speakers. I have an interesting story.  One of the midranges on a Nola speaker blew.  I called Nola; much to my surprise, Mr. Marchisotto answered the phone.  Nola did not have a replacement midrange, but he spent a half an hour on the phone with me talking about which speaker manufacturers made a suitable replacement.  Very impressed with him. 

Beyerdynamic headphones.

Cerious Technologies Cables.

Deja Vu Audio though they are a dealer that manufactures rather than a straight manufacturer.

Audio Note UK.

I'm sure there are a few others I am forgetting I'll add on if I remember any.

My experience with Pass Labs was exemplary.  I called them and a guy answered the phone and spent ten minutes or so with me discussing my issue and patiently answered all of my questions.  At the end of the conversation I thanked the guy and told him I appreciated his help....and I asked him what his name was, he replied "my name is Nelson Pass."

Another time I called them to ask the price of a power cord for one of my X-600 monoblocs....they sent me one for free.

I've had great experiences with Audio Research also.

Another nod for Modwright
Will add Daedalus Audio & Mojo Audio