Back in the late ’90s I was running a Cary SLP-90 with 12au7s in front of a pair of ARC VTM-120s that were configured with four 6550s a piece with some 6922s in front of them. I talked to Andy in Michigan and he sold me some NOS Mullard 12au7s for the pre and some NOS Amperex 6922s for the amps. After those tubes broke in a bit, that combination sounded fantastic. At the time I was running the amps with Svetlanta 6550s (either the 6550b or 6550C, I cannot remember) and I was so happy with the results of the other tubes Andy sold me that I called Andy back again and this time he sold me two quads of either NOS or vintage used Tung-Sol 6550s. Those cost me what I thought was an arm and a leg back then and I honestly couldn’t hear improvement.
I am not using the Cary right now and the ARCs are long gone; the stereo amp I am using right now takes a dozen EL34s and there is no way I am going to lay out what it would cost to go vintage used or NOS in that.
