Decided to attempt a reference thread where we compile a list of US-based audio companies and list them here as reference for anyone interested in supporting gear made in the USA. I'll monitor thread for replies containing new list entries and keep the second post updated. I did some digging and couldn't find any general "Made in the USA" threads but if such a thread already exists or any mods take issue, let me know and I'll remove it.
Edit 1: I'm not necessarily looking for 100% end-to-end manufacturing in the US, just companies that keep a large portion of their design/manufacturing stateside. For example, I would say Schiit Audio falls into this category as their products are designed, asembled, and tested in the US, even though the actual components themselves may not all be sourced from US suppliers.
Plussound Audio - Custom cables for IEMs, based in California.
