I turned my Leslie 145 up to about 7.5 and get this gritty distortion, not necessarily"the growl", but almost a Jimmy Greenspoon live sound. I don't want to burn up the driver. I rebuilt the cross-over and installed a new BB organ driver in it recently. The highest its been before was about 6. The pre-amp drive level on the AO-29 is set to one turn. When I turn it higher the difference in small, so I think this is more of a Leslie issue than a Hammond one. Basically, is it usual to have this level of distortion with the knob at this level.
1963 Hammond M-101
1969/70 Leslie 145