Manufacturers with great customer service

Pre and post sales support only, zero problems with gear though to be clear:

Arendal

Raven Audio

T+A (USA) was fast and helpful hooking me up with a local repair outfit if I needed it - I was inquiring about adding a module to the amp and didn't want to ship it anywhere.

Worst in the history of my audio life: Rogers Low Fidelity 

I’ll second @winoguy17 in siting Modwright. Dan has been nothing but exceptional in his willingness/ability to respond to questions about set-up, operation, tube issues, etc. I currently run his Phono Pre, LS99 Preamp, and KWA 99 monoblocks. Love them all… but maybe more importantly, love the fact that I picked them up, personally, from Dan in Amboy, WA. It adds a different layer to this hobby when you can meet/interact directly with the product’s designer and builder. Incredible eqipment. Great company. Full stop.

Although some have differing views on this next company, I’d also add Synergistic Research to this list. I bought their PowerCell SX used from a pretty prominent reseller. It came perfectly packaged, but after a few weeks, wasn’t operating as expected. On a whim, I, maybe out of desperation, I contacted Synergistic Research. They had me send them the USED piece. They repaired the USED/SECOND HAND item and returned it to me FREE OF CHARGE. It now works flawlessly. I’ve had many purchase/sale transactions… with and without stated warranty… I have rarely seen this level of service with a secondary buyer. They didn’t have to do that… yet they did. Least I can do is publicly give them that credit.

Benchmark, Oppo, Roon.

GR Research, Decware, PS Audio...all three very helpful and responsive, with great audio equipment.

TEK AUDIO SPECIALTIES. Todd provides great service. And support. Can't recommend him enough.