Also, Audio research can repair any product it’s ever made
But their build quality is kind of standard level. Aside from the knobs. I mean, it's not bad, but the choice of tubes and caps and circuit accounts for 100% of the sound of that gear. It's just basic sheet metal bent and silk screened with a nice front panel on it.
I'm not saying it's bad, but I wouldn't rate it at the top of construction and attention to detail. I'd rather call it perfectly utilitarian construction.
As for the sound quality, that is another story.