The Kora TB140 Integrated Amplifier ($5250) is an interesting hybrid affair, using both tubes and transistors to get you high (voltage) and current delivery as needed.
The Square Tube amps are not transistor amps preceded by tubes, but rather tube amplifiers aided by transistors. There’s a lot more to Kora’s Square Tube technology and I encourage those interested in learning about it to read Kora’s paper on the subject (PDF). For now, I’ll stick to the basics and point out that the Kora TB140 employs two triodes per channel as well as high current transistors (from Motorola) for a stated output of 2x 70wpc into 8 ohms and 100wpc into 4 ohms.
The TB140 offers four single-ended (RCA) line-level inputs, a MM Phono input, Pre-Out if you choose to use the TB140 as a power amplifier-only, a pair of speaker binding posts, the IEC inlet, and the power button all located on the unit’s back side. There’s an included remote that allows for a number of functions including the usual volume control and input selection. In addition a Setup menu provides access to adjust the level of the clic sound that accompanies volume level changes, display brightness, balance, input gain settings for each input so you can level match between sources, display style where you can display balance and offset info, and By-Pass mode when using the TB140 with an external preamplifier.
The Kora’s aluminum & steel chassis is a flecked Mineral Gray, while the front panel is about 3/4 glass behind which resides the yellow display. Rotating the flecked Mineral Gray circle to the right of the display with your fingertip adjusts the volume level. All in all, I find the Kora to be very nicely built and rather handsome to look at.
All of Kora’s products are designed and hand assembled in Toulouse, France.
Overall dimension: 118 x 420 x 370 mm
Unit weight: 9,5 kg
Manufacturer warranty: 5 years
Material: Aluminium & steel
Colour: Mineral gray
Accessories: Remote control, power supply cord, instruction manual
Construction & design: Toulouse, Occitanie region, France
Power source: Prise CEI, 230 V AC, +7% ~ -10%, (117 V AC on demand). Maximum power consumption (2 x 100 /4Ω) : 310 VA, Maximum power consumption (2 x 70 W/8 Ω) : 210 W
Internal power supply: 2 x (± 44 V DC), double power supply
Power supply transformer: 300 VA toroidal transformer Two 10 VA power transformers (auxiliary voltages)
Main filtering: 2 x 44 000 µF
High voltage: + 280 V Stabilized, – 180 V Stabilized
Heating of the inlet tubes: 2 x 12 V DC Regulated and ground references voltages
Heating of the outlet tubes: 2 x 12 V AC Isolated AC regulated voltages
Power output and distribution: 2 x 70 W/8 Ω, 2 x 100 W/4 Ω. Output power distribution made by four complementary highly linear – power transistors «MOTOROLA ®» (225 W/15 A each)
Inputs: Phono MM, internal impedance: 47 kΩ, sensibility: 4 mV, RIAA Correction. 4 entry lines, internal impedance: 15 kΩ, sensibility 1 V. Pre-out, impedance 2 kΩ, after volume adjustment
Passband: 20 Hz – 20 000 Hz ± 1 dB
Internal impedance: Output: < 0.08 Ω