Squeak,

I seriously doubt if the output is the problem. More often than not, hissing is caused by the lack of preamplification between the amp and keyboard. You can also create the same problem by cranking up the amp volume too high and having the keyboard volume too low.

First and foremost, test the keyboard's output by disconnecting everything and plugging a quality set of headphones into the headphone jack. If you don't hear the same hiss or humm sounds, then the problem is not in the keyboard.

If the keyboard's output is going directly into a multitrack recorder, you may have an impedience mismatch, which is also a common problem. Additionally, use the heaviest guage, sheilded, instrument cables you can find--they make a big difference in the amount of outside interference that's picked up from other instruments or pieces of equipment.

One last thing, make sure that all of the equipment is well grounded to a common, electrical ground. Essentially, this is done by plugging all of the equipment into the same power strip. Some wall outlets, especially in older homes and buildings, are not well grounded, which also poses a noise problem.

The relationship of your equipment to other noise generating devices can also be a problem. Florescent lights that run on ballast transformers create lots of 60hz interference. If your speaker or keyboard wiring is close to your computer moniter, this too creates lots of 60hz interference. I have an electric space heater than must be turned off when recording because of high frequency noise generated by the heating elements.

Hope this is of some help,

Gary