Only brands which broke new ground and were built in the research era of audio (1950's and 60s) where items were not made to a price, or have become design icons. They still are the best too, hence they keep their value. Point to point wired, great compoinents such as excellent transformers, and rare. Many cross over into professional gear though. Original vintage pieces not only don't depreciate but also appreciate:
Western Electric amps, speakers, vacuum tubes...anything!
RCA anything
GE, Brimar, Mullard, RCA, United, WE etc vacuum tubes
Altec Lansing horn speakers
Original early Audio Note Ongaku 211 amp
Early McIntosh amps
Studer reel to reels (C37/J37) & their domestic Revox tube variants
Philips 3501 1/4 inch reel to reel
Early Ampex reel to reels
Some PYE items
Braun...all items
Garrard 301 turntable
Telefunken anything
Neuman microphones
early Nagaoka and Decca cartridges
EMT turntables
Early Ortofon cartridges and original Ortofon Danish long tonearms
Early Quad amps and electrostatic speakers
Early Tannoy speakers
Linn LP12, Technics SL1200, older Thorens, some Lenco etc
There's a lot more omitted here, especially early US, but you get my drift.
Very little modern because the VAT is lost immediately, many are mass produced so not rare, then it has to stand the test of time to start to become a legend. Going forward, I'd subjectively gamble on these turntables to hold their value e.g. Simon Yorke S9 turntable, early Michell Transcriptor, TW Acustic, Brinkman, etc..not necessarily the best, but blend price, design, quality and rarity. Some tube amps Kondo, Shindo, AN etc, and some speakers and drivers e.g. vitavox and B&W Nautilus may retain value too. But it will not be across the whole brand. One will need to pick a specific piece. Tricky, so buy for enjoyment only.
