What makes A.N.T. Audio so very special?

Alex Nikitin who for 9 years worked as Chief Engineer for Creek Audio explains: 

Good sounding circuits can be developed in many different ways. Sometimes a new circuit idea appears, sometimes fine tuning and a careful selection of components for a well known circuit can produce great results, sometimes a particular device, like the famous 300B valve, shapes a whole range of designs.

The Kora 3T phono stage is a combination of rarely used but generally known topology with a particular type of a field-effect transistor (FET). The topology itself is known from valve electronics and I've used it successfully in many of my previous solid-state designs, with both bipolar transistors and FETs, starting from about 1980. However I was taken by surprise when I tried a particular FET in my phono stage circuit in February 2008. To my knowledge nobody had used that device in phono stages before, probably not even in audio applications in general - at least I've never met an audio circuit with this particular FET. I came across a number of these devices by accident, as I bought them for a non-audio application.  One day, after measuring some of their parameters (not listed in the datasheet) I decided to try these in the FET-only phono stage circuit that I was developing.

I did not expect much - my main interest was just to see if it was at all possible to use these devices in the audio field. I hooked a crude bread-boarded circuit to my usual vinyl setup, in place of my then current design, which was already considerably better than the previous best and well-respected phonostage I had designed for Creek Audio around 1995-1996 - the Creek OBH-8SE.   I was completely unprepared to what happened next - this simple, only 3 FET per channel circuit easily bettered my best previous efforts. Pretty soon I discovered that the circuit can be precisely tuned for the best sound with a particular cartridge by changing a DC operating point of the FETs in a certain range by adjusting a simple rear panel pot.

I then built several prototypes and sent these out to few friends with good vinyl experience. After a while one of them, from the US, asked me if I could make another version for him, using the best premium components and the best building techniques available to me. I did that for him and his response was that he could not believe the quality of the sound and musical nature of that small box. In his opinion it sounded better that his previous best choice - a custom modified EAR no less!

The result of this development was the Kora 3T phonostage - produced in two versions the "Special Edition" and the "Limited Edition".  Both share exactly the same electrical circuit, the difference made only by component quality and the selection criteria of the FET's used.  Later in the year, at the request of some of my friends and customers, I started the development of the MC version. In September I met Dave Cawley at Heathrow Show and he encouraged me to put more effort into the MC design. So by November 2008 the Kora 3T MC was born, both in SE and LE variants. The higher gain required for MC forced me to add one more FET per channel but I've kept the "3T" in the name even though "4T" might be more appropriate.

I can add a few words about the circuit I've used - it is a single-ended class A voltage amplifying stage and an output follower, EQ is passive, there is no global feedback. But these are all technical terms and such techniques are used by many manufacturers. What makes the Kora 3T design unique is a marriage made in heaven - between a particular topology and a particular device, a rare combination of properties resulting in a top quality sound. And sorry, no, I am not going to tell you what device it is. There should be some mysteries in this world.

Hi Fi World July 2009

In a review of six phonostages, the most expensive being £2,000, they said "The first podium position goes to the A.N.T. Kora 3T Ltd.  I loved the sheer musicality of this unassuming little box, it entices the listener into the music in a totally unforced way that's as effortless as it is beguiling."  The review goes on and on.

The even better news?  The wallwart has been banished and we now supply a lovely desk top power supply with all versions.

Power supplies

The standard switch mode PSU for SE & Classic models.  Unlike a lot of SMPS this unit is built to our specification with extraordinarily low RFI and no EMI at all.  These sort of SMPS's are often used in medical applications.  With an input range of 90 - 253 volts 50/60Hz it will work from the low voltage areas of Japan to the high voltages in the UK, and everywhere else in fact!	For Ltd. models this fully fledged linear power supply has virtually no RFI or EMI.  It has been designed with the best available components:  Panasonic FC low ESR capacitors, National Semiconductor LM317HVT regulator in low noise configuration, schottky rectifiers and a 2 ounce plated through printed circuit board.  All this is hand made near Cambridge in the UK.	This interior photograph of our Ltd. linear power supply shows the Panasonic FC capacitors.  One way to get a very low output impedance is to use a large storage capacitor and  that is exactly what we do as you can see. There are two versions:  90-126V for 100/110/120 volt 50/60Hz and 216-253V for 220/230/240 volt 50/60Hz power.

David Price editor of Hi Fi World said of the Ltd. linear PSU " It's gorgeous.  Changes the sound surprisingly much actually. Makes it ..  more explicit.   Big difference through my system."