I'm not sure that you'll find a lot of agreement on what constitues a "boutique" amplifier. For most products, that label implies cost and exclusivity. Literally, the word boutique is French for "small shop".
My take on boutique amplifiers probably doesn't agree with most peoples', but I think it makes more sense: I define a boutique amplifier as any modern handwired non-PCB amp. To me, that makes a lot more sense than the "it's boutique because it's sold to people who buy boutique amps" definition, which is disturbingly self-referential.
So in my world, there are three kinds of amps:
- vintage (self-explanatory)
- boutique (see above)
- production (any amp that uses modern construction techniques, specifically PC boards)
Here are some examples:
- Fender Vibro-King, Gibson Goldtone GA-5: boutique
- Diezel VH-4, Fender Blues Jr.: production
- Marshall Plexi, Silvertone 1482: vintage
Yes, my classification knocks some very popular and expensive amps out of their cushy "boutique" category. To me they're just expensive production amps built in small quantities. There's nothing inherent in the design or construction of one of these amps that would prevent the manufacturer from farming out the labor to a factory in China. The only thing that prevents a PCB amp from being manufactured in vast quantities is the market. There's nothing inherently better about a PCB amp that's only built in limited quantities. The price may be inflated by the manufacturer's choice of higher-quality components, but it's more likely that most of the additional cost goes to hand labor. But hand labor in the assembly of a PCB amp adds only cost. The PCB assures identical layout and consistent, repeatable results whether assembled by the company's owner or by a machine.
Amps that are handmade without PC board construction involve a higher level of craftsmanship and tend to vary more from unit to unit. Lead dress affects the tone of these amps, so it takes a certain amount of knowledge and skill to build them properly. And the labor-intensive nature of building these amps virtually guarantees that they'll never be made in huge quantities. That's why I think that handwired amps are truly boutique amps, while all the high-priced, limited-production PCB amps are still just production amps.