The power conditioner Audes ST-900 is designed to supply electrical power to High-End and Hi-Fi AV equipment. It comes with five outlets with the total power handling of 900 W. The main element of the device is a balancing toroidal transformer 230 VAC/115 + 115 VAC designed and developed by Audes, which isolates the equipment from the domestic network. Despite the significant power rating of such transformers the construction of the power conditioner completely excludes harmful electromagnetic radiation.

Special winding technique of the transformer and high-quality transformer core are used. First of all, they provide for the filtering effect. The ST-900 transformer was designed to work as a low-pass filter with a cut-off at 800 Hz, since all electrical network interferences happen at much higher frequencies. Secondly, the filtering effect is caused by self-inductance of a very large core, because of which magnetic flux cannot change instantaneously under a transient disturbance. Finally, if a DC offset is present in the mains, the transformer prevents it from reaching equipment, which is connected to the power conditioner. High-quality CEE 7/3 sockets are galvanically isolated from an external electrical network. The transformer is equipped with a reliable electrostatic shield. Arriving electrical interferences are counteracted using a mutual cancellation principle. The secondary winding of the transformer is separated into two halves and has an artificial centre tap, which is connected to the earth clips of each socket outlet. All of the above technical aspects allow to almost entirely remove electrical network noises providing reliable high-quality power supply to audio equipment.

Using ST-900 with any AV equipment, including both solid state and tube devices, improves the quality of sound reproduction. The most significant results are achieved when the power conditioner is used with power amplifiers. During highly dynamic parts of an audio a powerful amplifier must draw substantial current surges from a power supply unit, which can reach magnitudes of 50–100 A, while maintaining voltage levels without dips. An ordinary domestic socket, which is connected to a distribution board using long electrical cables, is not capable of providing such current levels due to relatively high output impedance. ST-900 has a very small output DC resistance therefore it can easily supply high current surges without facing voltage dips. This is achieved by using a transformer with a very large core and a high number of turns in the primary winding. As a result, the inductance is minimised. In turn the response time of a power amplifier to a changing audio signal is reduced, which benefits reproduction of transients, especially in lower frequency bands. An audio reproduction system exhibits a wider dynamic range.

Audes power conditioners have an overload protection and a thermal protection, which switches the transformer off if temperature of the transformer reaches 90 °C. Once the temperature drops to 75 °C the device will reconnect to the electrical network automatically.

Technical Specifications

Power rating

900 V∙A


10 A Inlet IEC C14


5 × 16 A/250 VAC Socket CEE 7/3

Power Supply Cable

10 A/250 VAC Connector IEC C13

Dimensions (mm)

130 H × 477 W × 347 D

Dimensions (inches)

5⅛" H × 18⅞" W × 13¾" D


11 kg/25 lbs