Well, look at it this way---a PVA at the Brass Bow will cost you about $135 dollars. At worst, you'll be out just over a hundred bucks. At best, you'll get back a horn that plays and sounds noticeably better.

I got my Constellation back from the Brass Bow a little over a week ago and these guys do the most incredible work on valves. The horn had to have the valves replated so I can't say what the difference would be with just a PVA.

I can tell you that this horn now has the best valve action I've ever felt on a horn. The valves were replated, hand fitted and then PVA"ed. It is not a cheap process and I'd have to agree that's the reason why most manufactuers don't do this. Another reason is that you have to have very skilled individuals doing this type of work and the work takes time. If you are a manufacturer mass producing a line of horns, you don't have the time to put into fitting valve clusters by hand with precise alignments. You would be intent on turning out enough horns to meet demand.

As for why do horn makers keep on using felt? I don't know either--but even if they used the material used for a PVA it wouldn't make much difference. Unless the material is the right thickness the valves still won't line up.