medivierte
New member
I guess that your loose rca input had its internal ground lug very loose also, making bad ground contact and this unstability on ground reference level is specially harmful for this DC coupled, wide-bandwith amp. I guess that it may provoke the overheating you noticed. I am glad that Job have fixed quickly the problem .
I leave some general recommendations from the goldmund/Job people for cabling, electrical issues, etc...
The Goldmund Ultra-fast Electronics Idiosyncrasies
In order to reproduce the transients and the dynamics in music with a lifelike quality, the Goldmund electronics uses extremely wide bandwidth in their circuitry, with literally zero phase error and time error. This is the main difference in the way they are designed.
However, this extreme bandwidth in the circuitry is making the Goldmund electronics more susceptible to be affected by incorrect installation and cabling. When proper care is not applied to the cabling, the grounding and the AC power connection of a Goldmund system, severe RF problems may be created, with danger for the speakers and power amplifiers, as well as serious sonic degradation.
The following information must be reviewed carefully and applied properly for the system to be immune of these problems.
The best sounding grounding schemes
The most difficult and important connection in a top quality system is the ground connection.
If not properly made, hum, distortion and instability may be induced. As for balanced connection, that Goldmund strongly disapprove, a bad grounding connection may literally ruin the lifelike dynamics that any really up-to-date system may reproduce.
The schematics recommended by Goldmund is known as the "Star System" as used in top measurement laboratories working on small signal levels.
In a Star System, only one central component (usually the preamplifier or multi-channel processor) is connected to the building ground (through the AC line connection or directly to an earthing post), and all other components are not.The ground connection is then properly made by the signal ground and if good quality coaxial is used for interconnecting the components (as the Goldmund interconnects and Lineal cables), the full system is totally shielded. For a top Goldmund system, the use of such high quality coaxial cable is mandatory for sound quality, perfect shielding and speed of transfer.
By simply lifting the AC wire ground connection of all other components, the star system is immediately built. However, for safety reasons as well as local regulation application, it is even better to link each component to the central unit by an additional very thick ground wire, connected to the yellow earth binding post of the components. On the central unit (preamplifier, ...), the black (signal ground) and yellow (earth) post may then be linkedIf the AC line ground is of the highest quality, the grounding system will improve sound and noise floor. If not, a real building earthing post must be used to connect the yellow post and the AC line ground must be lifted from the AC line too. Be careful that this type of installation must be made and controlled by a qualified technician to provide the perfect safety and quality.
The AC line polarity
From country to country, and even building to building, the AC line polarity may vary. The effect on sound of a wrong AC polarity is not common knowledge and this specific problem is usually neglected.
On a fast system like a full Goldmund system, the sonic effect of reversing the polarity of the electronic components may be far from negligible.
To properly adjust the polarity of each components, there are two different methods : the experimental approach, and the scientific approach.
To detect the proper polarity using the experiemental approach, the full system must be compared in sound quality with successively each component reversed. Usually, the sound is immediately more dynamic and open when the polarity is correct. To test a full system is a tedious and very long process, each component acting with the others and the number of combination being very high. Be patient. In a top sounding system, the result may be dramatic.
If you prefer to use the scientific approach, read our AC Polarity Measurement page. You need to have a very good high impedance AC voltmeter with high sensitibility. In some areas, small accessories may be acuired to help you detect by a simple measurement which polarity is the best. But we will recommend the full approach
To invert each component's polarity, a quite practical solution is provided by the Goldmund AC-Curator which has a separate polarity switch for each low-level output makes the choice very easy, even if the near-perfect isolation provided makes it far less critical. For components directly connected to a wall plug, the use of a special adapter may be necessary.
The Cabling problems
Choice of cables in an audio system has been very much pushed as a way to improve any system in the press during the last decades. No need to come back on the fact that cables sound different. But what seems less understood is that the sound of a cable is very dependent of the connected components. There is no such thing as the absolute best cable for any type of connection.
In a Goldmund system where the speed of the signal is mandatory and kept very high throughout, coaxial is the only reasonable solution. It is not only the best solution for digital cables, or for interconnect, but is also the best solution for speaker cables.
In addition to the speed that coaxial may help to maintain, the perfect shielding that the best ones may provide is mandatory to avoid oscillations.
But there are also some additional tricks.
To insure a perfect stability in a system, the input cables (interconnects) of an amplifier must absolutely be kept apart from the output cables (speaker cables). Otherwise the high frequency antenna created by the shielding ground of the speaker cable may, if the system is imperfectly earthed, radiate to the ground of the input cable and create a high frequency loop, inducing oscillation of the power amplifier. Run the cables separate or cross them at right angles and your system will be totally immune to this effect.
More, when you use long interconnects to a stereo or multi-channel power amplifier, run them close together, to avoid creating ground loop which will induce hum or buzz if you are in a bad RF area.
And finally, when the choice exist, and you are using Goldmund interconnects and Speaker cables, choose to run longer Speaker cables and shorter interconnects rather than the opposite. Loss of quality is faster in long interconnects than in long Goldmund Speaker cables because the carried impedance is higher.
