Усилители мощности стерео — Kora TA480

The TA480 is the larger of the two Class AB stereo power amplifiers made by Kora in France, positioned above the TA240 in the TA range. Kora also builds Class A power amplifiers in its CSA series. It is derived from the TB400 integrated amplifier and pairs a valve voltage stage with a transistor output stage. The European launch price was EUR 15,290, and the price quoted for the United States is USD 20,000.

Key specs that matter

Kora rates the TA480 at 2 x 240 W into 8 ohm, and at 2 x 430 W into 4 ohm. Bandwidth is 20 Hz to 20,000 Hz within 1 dB, and output impedance is below 0.08 ohm. Connections comprise one unbalanced RCA input with an internal impedance of 10 kohm and one balanced XLR input at 20 kohm. Sensitivity is adjustable between 0.5 V and 5 V, and the amplifier reaches full power with a signal of about 500 mV. The mineral grey aluminium and steel case measures 450 mm wide, 148 mm high and 420 mm deep and weighs 27 kg. Maximum consumption is 1,050 VA into 4 ohm and 650 W into 8 ohm.

Engineering and use context

The front end, which handles input and voltage gain, is the Square Tube circuit, an operational amplifier built from four triodes per channel using ECC82 and ECC83 double triodes run in pure Class A. The Square Tube topology is a Kora design by Bruno Vander Elst. The ECC83 heaters run on direct current and the ECC82 heaters on alternating current. The valves work from stabilised rails of +300 V and -200 V instead of a single positive supply. The tubes provide the voltage amplification, while twelve complementary Motorola power transistors rated at 225 W and 15 A each deliver the current in a push-pull stage biased in Class AB. The dual mono supply uses two 500 VA transformers feeding rails of plus and minus 65 V DC per channel, with main filtering of 2 x 100,000 uF, plus five DC to DC modules and two linear regulators. A smoked Plexiglas front panel shows the valves, and a matrix display reports gain and the selected input. The input attenuator works from 0 dB to -40 dB in 1 dB steps, set with a single multifunction button or the supplied remote control.

Pairing

The TA480 needs a separate preamplifier, and Kora's own PR140 preamplifier from the 140 series can drive it. A source with XLR outputs connects to the balanced input. Two pairs of screw speaker terminals are fitted.

Alternatives

The Kora TA240 is the lower powered Class AB stereo model of the TA series, rated at 2 x 120 W.