The guitar output transformer (OT) is the one component in the amp that contributes the most to defining the sonic character of the amp. It stands to reason that just replacing the OT opens up a wide range of very real tone changes to your amp. Although,the replacement OT's offered by different transformer manufactures claim the same specs, and will all work, each will more than likely provide a different tone and feel when installed in your amp. It is not the case that stated OT specs are miss stated, but every transformer is also characterized by many execution and design specs that are not stated. In a future "fake book" entry, the performance differences between various OT's will be examined and explained. With long history of working with and evaluating most of the commercially produced guitar OT's, it has been my experience that the transformers that come out of "Mercury Magnetics" consistently provide superior tonal performance. I find that this is the case with not only with available replacement OT's but also with the amp's original stock OT. To date, I have not replaced an amp OT with a "Mercury Magnetics" transformer, that there has not been a significant improvement in tone.