Doug: thanks for the detailed answers and the photo. If I understand what I'm looking at, the piston ports are oval for the compensating loop but round for the non-compensating loop?
I've never played a top-sprung valve set. Does it use the same springs? How do you replace the springs when they start losing resilience?
Dean L. Surkin
Mack Brass MACK-EU1150S, BB1 mouthpiece
Bach 36B trombone; Bach 6.5AL and Faxx 7C mouthpieces (pBone on loan to granddaughter)
Steinway 1902 Model A, restored by AC Pianocraft in 1988; Kawai MP8, Yamaha KX-76
See my avatar: Jazz (the black cockapoo; RIP) and Delilah (the cavapoo) keep me company while practicing