Most samplers and synths will run a lot quieter when using balanced power. Occasionally there are a few pieces of gear that will still have noise problems even with balanced power. Most of this equipment is music industry or semi-professional gear with unbalanced connections. The best way to approach this problem is to balance and isolate the audio signals by using audio isolation transformers, then run the balanced signals to the balanced inputs (or outputs) on the mixer. These are often much quieter than unbalanced connections.
By using balanced power and balancing sampler and synth connections, the noise floor of a keyboard setup can in many cases be reduced by 20 db or more. If the console only has unbalanced connections, unbalanced to unbalanced audio isolation transformers can be used with good results.
With balanced power, it is often possible to interface unbalanced outputs to balanced inputs without using audio isolation transformers and without inducing noise problems. If noise results, lifting the shield at Pin 1 of the balanced input will usually solve the problem. If it doesn’t, an isolation transformer or direct box will almost always work. Once most of the noise has been reduced by balanced power, it is easier to identify and solve problems.
See Equi=Tech Technical Support Bulletins: Audio Wiring and Grounding and The “Dirty Chassis” Condition for more information.