SoundCloud is good for posting audio clips.
A4, the A above Middle C, is usually where you start — seeing how close it is to 440hz (or 441 or 442 or whatever), deciding whether that’s where you want it, getting it where you want it, and then tuning the other keys to it.
I’m thinking maybe you find the sound of the M-37C harsh, brittle, brassy in comparison with the more muted sound of the Hohners, which some people find dull in comparison. The sound of the M-32C is less edgy. But if my thought is correct, you’d probably like a Yamaha.
Maybe your eardrums have been damaged, Gido, by playing your trombone at the airport.