01-03-2017, 11:17 AM
Typically 6A7 is not shielded, unless for some reason the mfr puts the shield around. If you do not have a bracket for it, you do not need it. In any case, if the shield were essential, you'd probably noticed some oddities in performance.
As for the microphonics of the 75, you probably got a particular tube with some loose element inside. As long as the new tube fixed it, you're OK. Often times the 75 if near the 42 is shielded and the grid cap should be INSIDE the shield. It being outside could cause oscillations. Are you sure you did not have it outside before changing?
As for the microphonics of the 75, you probably got a particular tube with some loose element inside. As long as the new tube fixed it, you're OK. Often times the 75 if near the 42 is shielded and the grid cap should be INSIDE the shield. It being outside could cause oscillations. Are you sure you did not have it outside before changing?
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
