I have a unique situation with some Sophia 6SN7 and 12AU7 tubes and wondering if anyone who has used these tubes can chime in.
In one of our preamps, every 6SN7 or 12AU7 we use are dead quiet except when we install the Sophia tubes. The Sophia's have a noise associated with them with the 12AU7s being the worse. When these same Sophia's are installed in one of our lower end units, they are quiet.
Anyone have any similar experience with Sophia tubes? I'm stumped.
