Product: Never-Connected power supply
Manufacturer: Never-Connected - UK
Reviewer: Nick Whetstone - TNT UK
Reviewed: June, 2007
If you are a TNT regular, and have even the smallest knowledge of hi-fi, then you most probably know how critical the power supply is to any piece of active hi-fi equipment. Often as much (or even more) work is put into designing and building the power supply than the circuit it powers. But no matter how well the power supply is designed and built, it is still at the mercy of the mains supply with all its noise, spikes, surges and dips. For that reason, many audiophiles have resorted to using various mains filters to counter the nasties. However, these filters often add their own problems by affecting the sound of the equipment, often making it sound softer, less dynamic etc.
One obvious alternative is to use battery power. But batteries are not ideal. For a start, they are really only suitable for lower powered devices like DACs, phono-stages, and pre amps etc. The arrival of the class-T amps running off a single 12 volt supply has made power amplification more practical with batteries, but (there is always a but in hi-fi) you can forget small batteries because they just don't provide the necessary 'clout'. They tend to sound slightly soft, and something the size of a car battery is really needed for optimal results. But a car battery should not be kept in a domestic room for reasons of safety, and long cables won't work optimally. And what if you want to power the whole system? You will need a stack of these large batteries and somewhere to locate them. Oh, and don't forget, you will need to work out a way of charging the batteries too such that they are charged when you want to listen! Oh, and did I mention the noise caused by chemical reactions within the battery? So batteries are not really the ideal solution.
What we want is a power supply with the (plug-and-play) convenience of mains connection, but one that is isolated from the mains problems in the way that a battery supply is. And that's what a Never-Connected power supply (hereafter N-C PSU) is. But how can it be connected to the mains supply, and yet keep the circuit it supplies isolated as well?
Well I am no electronics engineer, so this is only my take on it. The power comes from the rectifier bridge in pulses (that's why there is a big reservoir capacitor to smooth out the pulses and ensure a smooth supply). Now supposing some sort of timing device can detect when the rectifier is supplying power and when it is not, it should be possible to temporarily disconnect the power at those times. For obvious reasons, the supplier doesn't want to tell us exactly how it is done (at least not until the patent is granted) so it is one of those things in hi-fi that we just have to accept works 'somehow'!
The N-C PSU is one of several innovative products from a small company called Fenson and Co. They were good enough to let me have an evaluation board containing a regulated supply with a variable output. When it arrived, I connected it to a suitable transformer and put it all in a box with a switch and fuse etc. I adjusted the output voltage to 12 volts and added a suitable lead and plug to connect up my NOS Dacs and class-T amps.
Connecting the N-C PSU to a slightly modified Scott Nixon DacKit first, the results were very much as I expected. That is, the music had that slightly more relaxed presentation, as when using a battery supply. But there was none of the 'softness' that I had experienced when using batteries. I would say that the N-C PSU offered the best sound of the various supplies that I have used to date, ie linear regulated, battery, SMPS, and a modified linear supply originally designed to feed one of the Superclocks. I should say that I compared the N-C PSU with some good quality power supplies. If you should have one fitted to replace the typical PSU found in a lot of commercial hi-fi, you should expect to hear quite an improvement.
And surprise, surprise, the results were much the same when powering the class-T amps (Charlize and Autocostruire 2020). So the N-C PSU 'does what it says on the tin'. But it gets even better, because the advantages don't stop with the isolation of the mains supply. Because the N-C circuit can isolate each part of the equipment it supplies, it can prevent modulation of one supply by another. In plain English that means that one part of the circuit won't interfere with another. Take a typical CD player for instance. Ideally it should have separate supplies for the transport, DAC section, analogue output section, display, etc. Using N-C modules, it could still use a single transformer and yet keep the supply for each section totally isolated from the others. And the power supply for the display (well-known to 'pollute' the supply), won't feed back any 'nasties' to the rest of the CDP.
About now I can hear you saying where do I get hold of this wonderful new technology. Well, at present it is only available in the form of upgrades to existing equipment by specially appointed agents like Trichord . There is some new equipment that utilises the N-C technology including a pre amp from ECS, and integrated amplifier from Astintrew, phono stages from Trichord, and a motor-drive power supply from Michell. Sadly, the N-C PSU is not yet available to DIYers. However, with the quality of mains supplies becoming ever more dubious, it's good to know that there is a solution! For now, you will need to contact Trichord if you want N-C PSU technology in your own equipment.
© Copyright 2007 Nick Whetstone - www.tnt-audio.com