In the Jubilee series, the only mode that doesn't use diodes is the clean mode.
The overdrive channel includes two red LEDs and three 1N4007 diodes, and it's not possible to exclude them from the signal.
On the clean mode, you can activate the rhythm clip, which activates two more 1N4007 diodes at another point in the signal path for a light crunch.
This switch (rhythm clip), contrary to what many say, also affects the distortion channel, resulting in less bass and low-mids, less volume, and more compression.
Some people like it for harder rhythms.
So there's no such thing as diode-free distortion