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Reviewer: Chris Redmond
Financial Interests: click here
Source: AMR CD771
Preamp: Music First silver TVC
Amplifier: E.A.R. 509 monos, Border Patrol WE300B
Speakers: Audio Note AN/E Silver Sig, Dynaudio Contour 1.3Mk2s
Cables: Kimber Select KS-1030 silver, Kimber Select KS-3035 silver/copper, Artisan Silver Dream, Kimber High Current, JPS Kaptovator
Stands: Single sand-filled column Atacama for Dynaudios, Finite Elemente Spider Rack for components, Townsend isolation platform for AMR CD77, Targer wall shelves for AN/E outboard crossovers
Power delivery: PS Audio P600 multi-wave, separate Kimber High Current mains spur
Sundry accessories: Acoustic System Resonators and sugar cubes
Room size: 70 cubic meters
Review Component Retail: $2.399/pr (300Bs extra)

Living with the Border Patrol WE 300B amps for many years, my encounter with the far more powerful Abbingdon Music Research tube hybrid integrated had suggested the need for more muscle in my crib. How to maintain the 300B sound but add power and control? This became the basis for some personal research into available options. It eventually landed me at DIY HiFi Supply, its founder Brian Cherry and certain technical insights and the design philosophy behind his Lux 91 monaural amplifiers. After looking for past 6moons reviews of DIY HiFi Supply products to avoid repeating previous company history and not finding any, I asked Brian to take time out from his busy schedule and explain the origins of DIY HiFi Supply, where they are now as a company and where they intend to be in the future on products:


"I am Canadian and my wife is from Hong Kong. I came to Hong Kong in 1997 and worked for a company qualifying Chinese factories to do business with a large office technology company in the USA. I was frankly surprised by how many had risen above the sweat shops and were employing leading-edge technology processes in modern industrial districts. That’s when I started thinking about opening my business and sourcing the main components from China. I had many fond memories of building many kits by Heathkit, Allied, Knight, Eico, Dynaco et al and often thought how nice it  would be to see a resurgence of that part of life from the 50s and 60s. Some informal surveys were positive in that direction.


"For the first five years, we focused on the value-priced sector and began with converting discontinued Chinese-made retail tube products into DIY kits. We reworked their circuits to improve performance and added parts options never found in their price range. Our tube-rectified 300B monoblocks for example sold for US $700 at the time. Then two things happened. In the space of about 24 months, Chinese manufacturing costs shot up x 1.5 to 3 depending on commodity; and high-end hifi resellers were dropping like flies. I decided to move our products upmarket by loading them with even more extreme quality parts and hardware and by using unique and advanced circuit topologies from leading designers. Features like all film-cap power supplies, VCS filament supplies, Teflon tube sockets and circuit details like the reactive interstage found in the Lux series became our baseline standard. On performance, this kick up the ladder put us head to head with some very expensive gear. On pricing however, it’s a different story. The multi layer hifi distribution channel (typically factory to distributor/rep to dealer) ends up with mark ups at 6 to 10 times the manufacturing cost. As we sell direct to the customer, our prices in most cases are half to one quarter of typical high-end stickers. The trade-off for us is flying below the radar and that there likely is no local agent to provide service. Although not the norm, this business model has worked well for us over the last 10 years."

"We are nine people and mostly sell over the Internet although we do have a brick and mortar address in Shatin/Hong Kong and a small group of specialist hobbyist dealers. We sell about 50% kits and custom builds and 50% parts and modules even though in the beginning it was kits exclusively. Our sales are pretty evenly scattered across most countries - USA, UK, Germany, France, Benelux, Spain, Canada, NZ, Australia, Russia, with a few sales to Korea, Japan, Thailand, Malaysia and China. Our business style is to source hardware components globally, then consolidate the designs here in Hong Kong. Until now, engineering and design resources came from the UK/US and China.


"Our direction now is to combine proven Golden Age designs with leading-edge technologies and parts. We recently released our Tram 2 OTL linestage using a simple 2A3/45 direct-heated triode circuit supported by our 'big L small C' all film-cap power supply and remote volume control all in one chassis which I believe is a world first. This was difficult to work out and involved several prototypes over many months. The next 'world first' will be our forthcoming Crescendo speaker system at 100dB in-room sensitivity all in a 30-liter box. This only became possible thanks to recently available large horn ribbons and specific carbon-fiber mid/woofers. I am also excited that we are finally able to shake off the crippling 16bit/44kHz Redbook CD standard we never wanted and can get on with 24-bit/192kHz or higher formats. This is the biggest step forward since vinyl LP. Our Cleo USB DAC does 24/192 with tubes because it sounds far better. There is more but I won't be the spoiler."

I next asked Brian for specifics on my new amplifiers: Described as DIY HiFi Supply's best amplifier ever, the Lux 91 SET Mono Max is a refinement of the Western Electric 91 circuit originally designed to power cinema speakers, typically horns with around 100dB sensitivity. What about this circuit made it a suitable starting point for earlier DIY HiFi Supply amps and now the new Mono Max amps?


"When Joe Roberts published an article titled "The 300B Amplifier: A Model 91 for 1992” in the Summer 1992 edition of the seminal and lamented Sound Practices magazine, the 91 amplifier design was nearly 60 years old already. Since the late 70s, It had also been rediscovered by enthusiasts in Japan, Germany and France. Just as Helen of Troy has been called the face that launched a thousand ships, the WE 91 article and amplifier it described could be said to have launched thousands of enthusiasts onto the seas of single-ended amplifiers and quite a few boutique manufacturers of SE amplifiers as well. It was the compelling musical and realistic presentation of this amplifier that reopened the general market to low-powered single-ended amplifiers.


"Over the years the magic spell of the WE 91 design has faded again and not just in America and England. The original 91 design had many limitations dictated by the concept of high fidelity for Cinema Sound in the 1930s. The low-frequency extension is not great and neither is the high-frequency response. The 91 magic for the original at least was strictly in the midrange.

"The other issue with the WE 91 is that its limitations in the treble are hard to overcome whilst it's easy to give the amplifier low-reaching bass. However, such an amplifier then no longer sounds balanced as the HF limit is not raised in line with deepening the bass. The WE 91 also has a major disadvantage in power. Its driver stage is very high impedance. Where a low-impedance triode driver circuit can get over 12 watts out of a 300B run with the same operating values as the WE 91, the latter only brings a measly 7 watts to the table. If it overloads, it does so not with the gentle compression many triode-driven designs show but clips as a hard straight line just like a transistor amplifier. One could thus describe the original WE 91 as a gentleman's amplifier. Its forté never was at the extremes but in the middle. This made it more suited to civilized small-scale music than large overly noisy pieces. So perhaps it no longer was an amplifier for the 90s, certainly not this Millenium."

"Nowadays many designers seem to take pleasure tacking complexity upon complexity atop something as simple as a 300B SET. The most extreme design in this direction may very well be Bob Hoekstra's Axiom which uses seven signal tubes and three rectifiers. Many such amplifiers of course may be described as beating the proverbial crap out of the WE 91 on bass, treble and power. Yet at the core they often lack the natural, immediate and delicate sound of the WE 91 design. Only a few manufacturers other than Western Electric ever dared to put the original 91 circuit in minimally changed form to market as a commercial product. The highly acclaimed Harmonix/Reimyo 300B amplifier is a modernized WE 91 and the Yamamoto range of SE amplifiers are at least spiritual heirs though implemented in more modernized form with more modern driver tubes.


"Of course we have offered a kit that closely follows the WE 91 circuit since 2006. Our upgrades extend low and high frequency response to something a little more in line with modern expectations. Yet while excelling in musicality, immediacy and dare one say SET magic, this amp is by no means a hell raiser or suited to speakers with efficiencies lower than ca. 97-100+dB/W/m. Still, used carefully within the limitations it imposes, the WE 91-based Lady Day 91 remained for a long time our best-sounding amplifier. Taking it as our new starting point now was not only natural but essential.  Any amp seeking to displace the Lady Day 91 on our catalogue's very top would have to do everything the Lady Day did well plus address what the Lady Day 91 didn’t (power, dynamic range and clipping/overload behavior)."
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