I am not a climate change zealot, nor a great fan of the Renewable Obligations imposed on power-generating companies by the previous Labour government. I am however alarmed by recent price hikes in electricity bills, partly the result of Renewable Obligations, and threats of more to come. During a lifetime spent fiddling with music systems I have owned two Class A amplifiers – a 20W integrated Sugden and a 25W Audio Innovations – both of which emitted serious amounts of heat – almost enough to warm my living room. That wasn’t a consideration in heady post flower-power days when electricity was cheap and nobody gave a damn about how much they consumed, but thirty years on all that has changed.
I was therefore intrigued to hear about the launch of Hypex ultra-efficient Class D UcD (universal class D) modules six years ago. I investigated and discovered that Hypex didn’t embark on UcD technology until 2005 when they hired Bruno Putzeys, inventor of UcD when chief engineer at Philips, as head of R&D. More surprising was that Hypex were then, and still are, offering UcD180ST modules at an extremely affordable €60 each. It dawned on me that it would be feasible and economical to build my own amplifier; then indolence struck and I did nothing about it for several months.
My interest in cracking on with this DIY project was reignited after reading a positive review in Stereophile of Channel Islands’ Audio D-100 class D monoblock amplifiers, which use identical Hypex UcD180 modules. At around $1,800 a pair, the diminutive Channel Islands cuboids are not particularly cheap, nor likely to be affordable to most folk in our new age of austerity. Just like when I was a lad being reared in the aftermath of World War 2, it’s time to mend and make do, or engage in DIY.
Car boot casework
As I had never listened to music played through a Class D amplifier, building a DIY prototype was an act of faith and it was perhaps foolish to have unerring trust in just one favourable review. Although adept at DIY, this project was to prove challenging, particularly when sourcing casework. I originally hoped to find a clapped out amplifier at a car boot sale and strip out its guts, but eventually realised that would take too much time and effort with no guarantee of success.
I therefore opted to build my own enclosure using an 18-gauge polished solid copper etching plate (sourced from a fine art materials supplier) for the chassis, which a friendly local sheet metalworker folded at minimal cost. Side cheeks are offcuts of solid English oak floorboards, cut and planed to size. Other hardware came from disparate sources: B&Q, useful for small aluminium framing angles; Orbital Fasteners, who stock a range of stainless steel Resistorx button-head security bolts and self-tapping screws; and a ship’s chandler, where I discovered some PTFE-sheathed marine-grade stranded copper cable for internal mains wiring at 60p a metre.
Unfortunately the Hypex modules went adrift for a few days in transit from Holland thanks to a courier service that claimed my address didn’t exist; other electronics and hardware were sourced from RS without mishap. At the time there were rumours that RS would only sell electronic components to business users but I found this wasn’t correct. I called RS to check, was given an account number, placed an order by ‘phone and a large box arrived the following morning – an excellent service. One thing to bear in mind is that RS has a minimum delivery charge, so components should be ordered in a single batch to avoid excessive transport costs.
Instead of a transformer-based linear power supply recommended at the time by Hypex, each module is fed by Lambda switch-mode power supply smoothed by a pair of 10,000uF BHC/Aerovox capacitors – in essence it’s a dual mono amplifier in a single enclosure. Module heatsinks and power supplies are bolted onto the copper chassis base to ensure good heat transfer and cooling, not that there’s much cooling to worry about; in sharp contrast to Class A amplifiers these modules barely get warm even when powered up for long periods.
Aside from the logistics of sourcing components from numerous sources and trying to synchronise deliveries, the final stage of assembly was simple and painless, the whole amplifier taking less than two days to complete. I was grateful to have my electronics whiz-kid nephew on hand to oversee the internal wiring and prevent the amplifier from bursting into flames when first switched on. One of the more interesting characteristics of Hypex modules is that they are >90% efficient and combined with the two power supplies draw a steady 44 watts in idle mode or under load – hardly a major contributor to global warming.
Before building the Hypex amplifier I had for many years been using a Leak Stereo 20 amplifier, which produced ethereal sounds when used with sensitive speakers. Five years ago I acquired some ex-BBC Harbeth Monitor 20 speakers, which the Leak struggled manfully to cope with due to their low sensitivity of 83 db/W. In contrast, a Hypex module-based amplifier is immune to whatever load is presented to it and doesn’t change any basic characteristics – a ruler-flat response and hefty power output of 180 watts into 4Ω or 105 watts into 8Ω – all from modules no larger than a pair of cigarette packets!
The technical specifications of Hypex modules seem beyond reproach, but what of sound quality? In a word staggering. Power and dynamics are effortless and able to drive my Harbeths with ease, showing no hint of strain or edginess, even at high volume. The soundstage is wide, deep and spacious on a par with a high-end valve amplifier. For instance, when listening to solo acoustic piano – in my view the best test of any system – I believed Keith Jarrett’s Steinway in The Carnegie Hall Concert was actually in my room.
I have proved beyond doubt that at a total cost of £375 an amplifier based on Hypex UcD180 modules is astonishingly good value for money and would recommend them to anyone who has limited financial resources but aspires to high quality sound. Another benefit of Hypex amplifiers is that they weigh no more than three or four kilos, so there’s no need to lug 30Kg behemoths around and manoeuvre them into place. So it’s a fine amp and not just for music lovers, but also for anyone who suffers from lower back pain.
The next step is another prototype with smaller switch-mode power supplies drip-charging soup-can sized capacitors; that’s on hold while I deal with a backlog of mundane domestic DIY projects, but it’s going to be an absorbing project during dark, dank winter evenings.
Hypex nowadays offer a wide range of high performance UcD modules with outputs from 180 watts to 700 watts, plus voltage regulators and high-efficiency switch-mode power supplies. Anyone wanting to discover more about these tiny modules should look at the Hypex website at https://www.hypex.nl/ and drool.