Development of the now legendary and much copied NCC200 module has at last now reached its full potential. Originally published in an RCA manual in the 1970s, the circuit was used by Naim Audio in a succession of well regarded amplifiers still being made today. Les’s development of the circuit has been well received over many years with some 3000 NCC modules giving lasting pleasure in all corners of the audio enthusiasts world.
The RCA circuit, conceived during the 1960s, was limited by the choice of transistors of the day. Output transistors to carry more than around ten Amps just did not exist and then only in NPN versions. The architecture of the RCA circuit is what is known as ‘Quasi – Complementary’ where one of the output devices is installed reverse biased, or to the layman – facing backwards. This requires adding certain elements to the circuit to ‘fool’ the driving circuits into believing they are providing a signal to a fully complementary circuit. These extra bits of circuitry introduce a whole new set of problems in the amplifier’s performance and even more compensating bits and pieces have to be incorporated to ensure some semblance of a linear performance. Unfortunately, the perception is a slight artifice in the sound where a loss of detail along with a minor high frequency masking element is still evident.
In recognition of the drawbacks of the RCA system, Les decided some years ago to move away from the shortcomings by designing out the logjam of the quasi comp architecture and replacing it by a fully complementary output system – hence the Qudos modules now available. Utilising the best elements of the RCA circuit which have proved to be reliable over many years, Les added a conventional output pair of devices which enabled the removal of all the former compensation known to cause sonic aberration in the sound quality. An entirely new printed circuit board with plated through component pads enabled each part to be soldered on both sides of the PCB, something rare in the audio field. Eliminating largely the possibility of any future dry joints has to be a plus for any owner in the long term. Gold plating the PCB avoids the risk of corrosion causing faults again, reliability being the criteria here. With an expected service life of well over 30 years without the need for ritual visits to the manufacturer, the owners of these beautifully built and presented modules may sit back in confidence and enjoy the sounds.
Compliments on the sound quality of the Qudos just keep rolling in as the list of users grows by the week. Available, as customary, on a 60 day sale-or-return basis, these represent a simple plug-and-play module – a direct replacement for most Naim power amplifiers and as easily fitted as a 13A plug for most owners.