Hi All,
If you've done a search on JTM 45 mods, the info available is overwhelming. For a quick easy reversible mod that worked for me, change the Phase Inverter tube from a 12AX7 to a 12AT7( like a Fender amp). I'm running the amp jumpered (both low input channels) and running my guitar into the bright channel. To get the sound I like from a humbucker guitar (SG stock pickups) is to have the Bright Volume at 6.5 and Normal at 5.5 or so, Bass at 2-3, Mid at about 9, Treble at 3:00, Presence at 3:00. Using these settings with a 12AX7 gets me bass that is a little less defined than I like. When I changed the the PI tube to 12AT7, the overdrive characteristics were reduced very slightly but the bass became more defined. I just increased the volume on both channels slightly and perfect. (like old ZZ Top). 5 and down on the guitar volume is clean, 7 is crunchy and 10 is a good lead sound. (no overdrive pedals required) Your mileage may vary depending on what you are looking for. To save my hearing I needed to test this with an attenuator, but I verified the sound without it. I was reading on mods to reduce some flubby bass and this was one of "Non-mods" from George Metropoulos. Have fun.
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