There is an early VDO clip (by Sofirn?) showing the prototype. No rotary switch 
. Ramping seems the regular, perceptually non-uniform variety.
And of course: Sofirn Go
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There is an early VDO clip (by Sofirn?) showing the prototype. No rotary switch . Ramping seems the regular, perceptually non-uniform variety.
And of course: Sofirn Go