A Weird One

[clyde]

For your interest (I hope).  I was messing around with an EF86 in an amp, trying out different cathode caps as I hadn't bypassed in the original iteration.  Subbing them in didn't seem to make any difference to tone or gain.  I lifted the cathode resistor and subbed in different values with a decade box, same result, 1M and 10 ohms sounded the same, as did totally unhooking the cathode!!!??  So somehow the signal is coupling through the tube without needing the cathode.  Hmm, the tube tested fine in my tester so once again all connections were checked, double-checked.  Pins 2 and 7 were grounded and when I unsoldered them from ground the ghost disappeared.  Trying another EF86 yielded no such anomaly.  Had me stumped for a bit.