The Carver C-19 pre has a tube buffer stage that gives it the tubey sound signature and also gives you a chance to play around with different tubes (I have rolled a few, using Bugle Boys now courtesy of Steve). The other thing you can change are he op amps, which are what really does the main job in this pre (you need to desolder the old op amps and install an op amp base, VHF did that for mine before I bought it from Rev). The first time around I used NE5532. Sound was good, but noisy. Last night I swapped in slightly better LME49720NA. Huge drop in noise, but the sound signature changed as well (not bad, but different). The dead quietness of these op amps has me slobbering for the possibility of what even better ones could do.
The next upgrade to the C-19 involves replacing all the RCA jacks with high quality ones. These RCAs are a pain in the ass to remove but worth redoing because the originals have outlived their usefulness (the hats keep falling off) and the connection to the board is not the best. I believe King had this done on his.
