Intro
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Ever heard of the French brand Kora? Neither did we until recently but we suspect that this will soon change enough. Dutch distributor Dimex has had Kora in its portfolio for a while now and we see the brand appearing more and more often. Kora has been around for a while but after 2014 it got a bit quiet until it relaunched in 2017 under the influence of Bruno Vander Elst. A brand where one man passionately tries to create something unique appeals to us. We like the underdog. Other brands that come to mind are Fredrik Lejonklou with his Baozu amplifier or Daniel Frauchiger’s Merason Frérot and DAC1 d/a converters, which we tested some time ago. But also products closer to home like the Driade loudspeakers by Arnold Heres, dacs and amplifiers by Cees Ruijtenberg or the cartridges made by A.J. Van den Hul belong in this category. All of them world class. We were allowed to play with the Kora TB140 integrated amplifier for some time and loved every minute of it!
Kora’s lineup includes two more integrated amplifiers (TB200 and TB400) and two power amplifiers (TA240 and TA480). A preamplifier and (surprisingly) a CD player are in the pipeline. All amplifiers come in black with grey accents. The combination of the black acrylic frontplate with the “mineral grey” aluminum housing is a good match. The oled display with yellow lights also works wonderfully. The volume and line input appear on the display. This information is, even at a great distance, perfectly readable. We like that.
With the volume knob you not only control the volume but you also use it to navigate the menu. This is done by pressing the volume knob briefly. A longer press turns the amp off. The menu is very straightforward and full of interesting functions. For example, you can control the gain of each, you can adjust the balance (a personal favorite), you can dim the screen or bypass the amplifier (input 4) should you want to. The small, plastic remote control works extremely well. We love the simple design because, as in the old days, the buttons rise above the remote. By the way, the more expensive TB200 and TB400 do come with a fancy, metal remote control.
Square Tube Technology
The Kora TB140 delivers 2 x 70 watts in Class A/B and are sufficient for 95 percent of all speakers on the market. Our 8 Ohm Revels with an 86db sensitivity were driven without a problem. Even more, the combination with the Revel is outstanding. There are five unbalanced inputs, one of which with a phono stage. There is also a pre-out if you ever want to connect a heavier poweramp. There are no balanced inputs but we didn’t miss them at all.
Bruno Vander Elst developed a special technique to provide his amplifiers with the purest possible signal. He uses tubes but does not do this in the usual way. He does this via his patented Square Tube Technology in which four tubes are used to control the preamplification. These four tubes provide a symmetrical signal and voltage at the output. The tubes only provide voltage and no current which makes them very long lasting. However, these tubes do not provide the final amplification. Bruno uses transistors for the current. This is what Kora has to say about their Square Tube Technology:
Four tubes are used to make a single amplification stage, hence the name! The SQUARE TUBE ” outputs ” a symmetrical signal with respect to the reference ( earth ). In other words, the signal goes alternately in the field of positive voltages (to push the diaphragm of the loudspeaker) and in the field of negative voltages (to pull the diaphragm). This unique capacity with vacuum tubes makes it particularly suitable for the design of audio amplifiers.
In your Kora amplifier, the SQUARE TUBE provides all the functions of amplification and control of the audio signal. At the output stage of the SQUARE TUBE, the signal is identical to the one which is input to the speakers. Complementary power transistors, audio and hyper-linear will give the current required by the speakers, but without interfering in the amplification of the signal
We sometimes complain that there is little or no innovation in our industry but provided you do some research you can still find it. Just think of the Purifi amplifiers by Bruno Putzeys or the Grimm MU1 streamer by Eelco Grimm to name a few. Innovation is much needed because as the saying goes: to stand still is to go backwards
