Интегральные усилители — Kora TB140

The TB140 is the lowest-powered of the three TB integrated amplifiers from Kora, the Toulouse maker that designs and assembles its electronics in the Occitania region of France. It is also the only TB model with a built-in phono input, and in France it sells for EUR 5,640. Like every Kora amplifier, it is built around the Square Tube circuit, a hybrid of valves and transistors.

Key specs that matter

Rated output is 2 x 70 W into 8 ohm and 2 x 100 W into 4 ohm, with 4 ohm given as the minimum speaker load. Four line inputs on RCA have an input impedance of 15 kOhm and a sensitivity of 1 V, while a fifth input serves moving magnet cartridges with 4 mV sensitivity, RIAA equalisation and a 47 kOhm load. A pre-out socket, taken after the volume control, has an impedance of 2 kOhm. Bandwidth is 20 Hz to 20 kHz within 1 dB, and speaker output impedance stays under 0.08 ohm. Overall size is 118 x 420 x 370 mm, the chassis alone is 100 x 420 x 340 mm, and the amplifier weighs 9.5 kg. Maximum draw reaches 210 W at full 8 ohm output and 310 VA at full 4 ohm output.

Engineering and use context

Four triodes per channel form the Square Tube stage, which handles all voltage gain and signal control. Four complementary ON Semi power transistors, each rated 225 W and 15 A, only supply current to the speakers - Kora compares them to an output transformer, but without the phase shifts at both frequency extremes or the current limit that a transformer brings. The supply combines a 300 VA toroidal transformer, two 10 VA auxiliary transformers and 2 x 44,000 uF of filtering on rails of plus and minus 44 V DC. The valves get stabilised +250 V and -165 V, with 12 V DC heating for the input tubes and 12 V AC for the output tubes. On this model the mains switch sits at the back beside the IEC socket, and a pre-charge circuit precedes start-up. A microcontroller watches the voltages while the valves heat up, then restores the last input and level. Input 4 can be switched to bypass so the TB140 works as a pure power amplifier. Kora builds the case from aluminium and steel with a mineral grey finish and covers the unit for five years.

Pairing

The MM input takes a turntable directly, while a moving coil cartridge would need an outside stage such as the Kora Phono Stage. Through its pre-out, the TB140 can feed a Kora TA240 in a bi-amplified system.

Alternatives

The Kora TB200 is the next integrated model up, rated at 2 x 100 W into 8 ohm but offering line inputs only.