Adams Brass (Netherlands / Holland) recently came out with a high-quality 4-valve non-compensating euphonium name "Sonic." It is essentially an E1 (a professional-level euphonium) but without the compensating system. Here is a comparison of the Sonic and the E1. It's important to note that the Sonic is about 2/3 the price of the E1. Part of this video was made at the Adams booth during the recent International Tuba-Euphonium Conference 2023 in Tempe, Arizona.