In most modern amplifiers, the input, output and power supply are all referenced to a common ground. Therefore, a variety of currents — such as ripple current created by rectification in the power supply and counterelectromotive current generated by speaker cone movement — flow through the grounding circuit. These currents create undesirable potential differences at various points within the grounding circuit. And these differences in turn affect the performance of the various amplifier circuits.
Balanced transmission
The solution is a "balanced" signal transmission system. After all, professional recording and radio studios have been using it for years to avoid ground-related problems. We discovered that when using a balanced system in an audio amplifier, in addition to a balanced input and output the power supply should be balanced — this is a significant departure from conventional thinking. Because, unlike professional equipment, an audio amplifier must amplify as well as transmit low-level signals. Also, the transformers commonly found in professional equipment should not be used for they limit frequency response and increase harmonic distortion.
X-Balanced Amp: Construction (Type I)
The new X-Balanced Amp does not use a transformer, and is able to transmit and drive electrically balanced signals. Therefore, it suffers from no ground-related problems. Of course, it has as low harmonic distortion and as wide frequency response as any current state-of-the-art amplifier.
As shown below, a balanced system is used in the input, in the output, in the power supply and even in the feedback loop. Since no circuit is referenced to the ground, the X-Balanced Amp is completely immune to ground-related problems. And since balancing is achieved purely electrically, it permits both high power and hi-fi reproduction.
In summary: since the grounding circuit, power supply and loads have no common electrical points, and since all circuits are of balanced configuration, current in the power supply, regardless how high it may be, cannot affect the signal. As a result, the X-Balanced Amp dramatically reduces IHM (Interface Hum Modulation), the type of dynamic noise caused by counterelectromotive current generated by speaker motion.
All in all, the X-Balanced Amp has brought about a tremendous improvement in reproduced sound quality — tighter definition, sonic purity, and a total freedom from noise.
One more benefit of the X-Balanced Amp: The ability to drive low impedances
The Sansui X-Balanced Amp has another unique capability: it can provide proportionally higher current when the speaker impedance falls to very low values. It is widely known that the impedance of a speaker varies considerably depending on frequency: a speaker nominally rated at
8 ohms can actually present to the amplifier a load of only 4, 3, or even 2 ohms at certain frequencies. As the impedance decreases, more current is drawn from the power amplifier.Recent recordings, particularly digital recordings, contain pulse-like transients, which require more current from the amplifier, more so at lower impedance. This means all amplifiers should have a high current supply capability, or a high dynamic power rating, to play newer, better sounding programs (digital music, for instance) at a realistic level without clipping, tripping protection circuitry or damaging the speakers.
Thanks to a rugged power supply, an efficient heat sink, and high-power transistors, the new X-Balanced Amp is able to feed sufficient current to the speaker even when the load goes as low as
2 ohms, and no matter how transient the signals are.
