Hi Bill,
I disagree.
First: The setup is the same as with the Tyros 3 and 4, so if one of my other equipment is causing the problem...why didn't I have this problem with the Tyros 3 and 4?
Second: On a Dutch forum (and also as confirmed by user clavier), I'm not the only Tyros 5 owner dealing with this problem.
I think that Bill's advice was a good one.
Here's some text copied from Bill Whitlock's paper, which might shed some light on the matter:
Bill Whitlock: UNDERSTANDING, FINDING, & ELIMINATING GROUND LOOPS IN AUDIO & VIDEO SYSTEMS
“A cable is a source of potential trouble connecting two other sources of potential trouble.” This
joke among electronic system engineers is worth keeping in mind.
Any signal accumulates noise as it flows through the equipment and cables in a system.
No system can be quieter than its noisiest link. Noise and interference must be prevented
along the entire signal path.
Furthermore, unbalanced interfaces are prone to noise problems, because they provide no common mode noise
rejection, like balanced interfaces do. Unbalanced interfaces are inherently extremely susceptible to power-line
noise.
THE FACTS OF LIFE ABOUT AC POWER
In all real equipment, there are parasitic capacitances between the power line and the
equipment ground. They are the unavoidable inter-winding capacitances of its power transformer
that are never shown in schematic diagrams. Especially if the equipment contains anything digital,
internal electro-magnetic interference (a.k.a. EMI) filters will further add to the capacitance. These
capacitances allow leakage current to flow between power line and chassis/ground inside each
piece of equipment.
In UL-approved ungrounded (i.e., 2-prong ac power plug) devices, this current is limited to
0.75 mA. Such equipment incorporates a number of protective mechanisms so that it remains safe
in spite of internal component failures, overload, and rough handling. Because this equipment is
ungrounded, it’s chassis (or input/output connections) can assume relatively high voltages with
respect to the ground system. Although a voltmeter may indicate well over 50 volts, the current
available is small and will cause only a slight tingle if it flows through a person. However, any
connection between two such devices or such a device and a grounded one will carry this leakage
current. We must accept this fact as reality.
HOW THE NOISE GETS IN
With ungrounded devices, power-line leakage current flows in the grounded signal conductor.
Since this conductor has resistance, a small noise voltage is generated over its length. Because
the interface is a series circuit, this noise voltage is directly added to the signal arriving at the
receiver. Because the impedance of the grounded conductor is "common" to both signal and noise
current paths, this mechanism is called common impedance coupling.
Common-impedance coupling can become very severe in an unbalanced interface between two
grounded devices. Any ground voltage difference developed in the building wiring, which generally
ranges from a few millivolts to a volt, is effectively impressed across the ends of the grounded
signal conductor, typically the cable shield.
SOLUTIONS
Devices called “ground isolators” solve the fundamental problem with unbalanced interfaces.
Broadly defined, they are differential responding devices with high common-mode rejection.
In order to solve the problem, an isolator must be installed in the signal path
at the point where the noise coupling actually occurs.
As I said in the post earlier, people have been able to get rid of this noise by
using a Hum Eliminator (Ground Loop Isolator) or a DI-Box, which are examples of "ground isolators"
mentioned above.
In summary the thing that is wrong with the Tyros models/series is that they all use unbalanced outputs
(and inputs).
Regards
Kari