Fixed: Aliasing issues with JP50 organs

[jalbert]

I've had lots of issues with the organs on the JP50 from severe aliasing that creates loud static noise when dissonances are played (or even octaves low on the keyboard). E.g. hit the Combo Organ button and hold down F1 and F2 on FullDBar01 or 02.

Turns out this is caused by the overdrive effect defaulting to 50. This effect is intended to simulate overdrive on the tube amp of a leslie speaker, and was not implemented well.

[orijinalca]

I just saw the first time from this website.

[jalbert]

The problem is easy to replicate with the keyboard-- it isn't subtle problem, but major distortion. I thought something was wrong with my keyboard, so I called Roland support, who walked me through the fix. The overdrive effect on the virtual tonewheel should be used judiciously. A little goes a long way. the default setting (at least what was set on my keyboard out of the box) was 50, which creates the severe distortion when dissonances are played, such as an Fmaj7 chord in the middle of the keyboard, or a parallel octave of F's at the bass region (F1 and F2).

Setting overdrive to zero addressed the issue immediately.

[kimsnarf]

I thought something was wrong with my keyboard, so I called Roland support, who walked me through the fix.

Thank you for researching this. I have wondered about the same thing. Unfortunately this bug makes distorted organs kind of limited. The lower the notes you play, the lower you have to set the distortion setting to avoid this issue. It is kind of like the PWM aliasing issue in reverse, where you have to avoid the upper notes.

[jalbert]

I'm not a huge fan of modeled overdrive anyway, but you probably have to sometimes vary the overdrive level from song to song. On the other hand, with a real leslie tube amp at higher volumes, the amp is in overdrive, like it or not, but with a DSP leslie effect, you can adjust volume/gain and distortion independently.

I generally view keyboards as different instruments from an instrument they simulate and figure out a good musical technique and expression for it, not try to mimic what happens on the instrument being simulated. This is especially true on acoustic instruments, not so much on organs, but the key click percussion and COSM overdrive effect are exceptions.