How far apart should the OT and PT be?
As far as you can get away with, without otherwise compromising the lead dress. If you aren’t sure, experiment. If they’re touching they’re too close. On separate planets is probably not worth the hassle or expense. -Miles • What causes a tube to be microphonic? Microphony is caused by instability or play in the internal structures of the tube. Since the various elements inside a tube have various voltages applied to them, and since (like any two pieces of metal which are in close proximity) there are various inter-element capacitances involved, when mechanical excitation is applied to the elements these capacitances change, causing a signal to be developed on the tube’s plate when, as a consequence of the changing capacitances, the voltages change. The more play there is in the internal structure, the more pronounced this effect will be. It is exaggerated in smaller tubes by the fact that the elements are in closer proximity and therefore smaller motions will cause larger signals to b
