I've been reading all I can find about tube amps for the last 6 months (and there is a huge amount out there) and am about to attempt my first project. What I want to build is a 1-tube practice amp, with an ecl86. I wanted to use an ecl80 (lower output) but apparently the shared cathode in that tube causes problems. My problem is that I don't see how I determine what to put in between the input jack and the grid of the triode. All the schematics I found (and there aren't many) use the tube for a small hi-fi amplifier, but the impedance of (for example) a CD player or tuner is obviously very different than that of a guitar pickup. I've been looking at the Champ schematic, but I'm not clear how the differences between a 12a?7 and the triode of the ecl86 affect the input. If someone could enlighten me, it would be helpful. Thanks.