Found this Princeton mod on Fenderguru.com Output transformer with multiple impedances (built-in attenuator) This mod requires the knowledge of how to replace a transformer in your amp. This mod will give you different speaker outputs impedances converting the the external speaker jack to an independent output. The original OT is sized for an 8 Ohm speaker impedance. It will make sure the power tubes “see” the correct impedance and can operate at optimal conditions in terms of clean headroom potential and frequency response. If you had an OT designed for a 2 ohm speaker load the tubes would operate at their best with a 2 ohm speaker load. If you use a 8 ohm speaker with a 2 ohm OT, the tubes are pushed harder since they see a bigger load than expected. Both volume and clean headroom is reduced significantly, and the tone is not significantly changed. This effect is similar to an attenuator, which is very nice when you want to achieve the amp’s sweet spot at lower volumes. The article goes on to describe how to install an OP transformer with multiple secondary windings for different levels of attenuation. I've read about the proverbial Rule of Thumb regarding impedance mismatching; that it's relatively safe if one doesn't overdo it. But what are the dangers of running a pair of 6V6s into a 6.6 kohm primary output transformer and driving an 8 ohm speaker with the 2 ohm secondary tap? It seems way outside the safe operating parameters. (This particular example is a mod for silverface Princeton Reverb. The intention being more breakup/distortion with less volume. IE sounding dimed at bedroom levels.) What sort of wear & tear would this place on the output tubes & transformer? Thanks!