Noises, hum, ground loop noise on my instrument.
Almost all our instruments are "Class II" that means they don't have the earth connection, they do not require it. Earth, ground, hum, ground loops and audio devices are not perfect science, so it can happen that you will experience digital noises or what is commonly called "ground loop".
As a result, this situation can cause an hum noise out from your speakers: it is important to know that, when you connect your instrument to another device (mixer, PA, computer) you have to consider the entire rig, not only your keyboard. Imagine that you have your Crumar instrument connected to a mixer (that maybe is class II), that mixer is connected to a PA system (that maybe is Class I) but you are also taking advantage of the USB type B connector of your instrument (or MIDI) to a complex digital or computer DAW or another keyboard.... and you have hum noise or ground loop. There isn't any universal solution to this problem, it's a matter of trying, disconnecting this or that, using other cables, disconnecting USB or using a better cable, change or swap the AC plugs. Sometimes the only solution is a DI box or a USB isolator.
You can also have the opposite situation: lack of ground... when this is happening you will hear the tipical noise of a cable without sleeve.
Another scenario you can encounter is a noise that you "think" it's a hum but as a matter of fact is not: the typical example are those instruments (Mojo61 or Mojo Classic for example) that have the VB3 sound onboard. VB3 is a simulation of a tonewheel organ, that famously is full of noises coming from its circuitry. Leakage and Cross talk are the most famous, but also the simulation of the leslie speaker has its own noises. Our instruments, simulate also the noises, keep this in mind: you can lower or cancel them using the editor or the software settings. Another example is the damper/sustain pedal noise on piano sounds: when you press the sustain pedal on a real piano or on an electromagnetic piano, there's a noise coming from the strings (or tines) or from the internal mechanisms of the instrument... this is normal and, OBVIOUSLY we simulated it too on our instruments! So it is not a fault but it is a feature... there's a setting for lower this too. So... if until now you played keyboards without this simulated noises, welcome to a new level of simulation :-)
Interesting videos:
https://www.youtube.com/watch?v=wkc7jVIqZ6g
https://www.youtube.com/watch?v=72WoueTI354&t=83s
https://www.youtube.com/watch?v=Jx_KlNFixmQ
Another source of noise can be the wifi module if your instrument is equipped with it or has it as an accessory: the noise produced by the wifi module is highly connected to the enviroment where your instrument is. Please keep in mind that it is mainly used for editing the instrument so you are not supposed to leave the wifi module connected to the instrument the whole time. If you are experiencing the noise, try to swap cables, change the location/position of your instrument. Sometimes the only solution is to use a USB cable extension type A male to type A female to move away the source of noise (wifi signals) from the audio circuits of the instrument, something like this: USB EXTENSION CORD
Some amplifiers, even if designed for keyboards or PA, can introduce or create or add noise to the normal audio sound. The kind of circuits we use in our instruments are designed for hi-quality output, balanced audio drivers are used (DRV135) ... it seems a non-sense but if you connect a musical instrument with professional circuitry design to some poorly designed amplifiers or old amplifiers we cannot guarantee that the end result will be as good as using a modern PA system and a modern mixer. Please do not use amplifiers designed for other instruments! (for example guitar amplifiers). Guitar amps are for guitars, Bass amps are for basses! Have you ever heard about input and output impedance? Also some mixers have dedicated inputs for keyboards, microphones, guitars, smarphones ecc ecc... they are not interchangeable.
Some of our instruments have a built-in audio out level selector. Please be sure to match it with your system. Using an incorrect output level can raise the noise level. https://en.wikipedia.org/wiki/Line_level. If the selector is not present, consider Ref level (pro). Also the settings of your mixer can affect the noise: gain and volume are two different things :-)
Another suggestion: please keep in mind that all our digital instruments have balanced line outs. It is of course compatible with unbalanced cables and jack... but... you are missing an opportunity here!
Please keep in mind that every keyboard is unique and has its own output circuit design, so saying "but all my other keyboards don't have this noise in the same amplifier!" is not a reference.
Last but not least: good and reliable audio cables!