I ordered some JJ Electronic tubes from Amazon and they just arrived. My Fisher uses 6 of these. They appear to work okay in the MPX and for tone but do not work at all in the pre-amp. My old tubes still work, I just wanted to get new ones and have the old ones as spares. So I contacted Amazon and they are replacing the order. FYI, the tubes were shipped loose in the box. There was a little packing material, and I mean little. So little you could hear the tubes rattle around shaking the box. I'm assuming the tubes are bad because of how they were packed. But I'm not 100% sure since they work in the tone and MPX application. I guess my forum question here is whether there's any possibility the tubes are fine and they are exposing a problem with the stereo? If the tubes are bad, how come they work in the MPX and tone functions? Just to be clear, my old 12AX7s work fine in the pre-amp application.