My Audio Odyssey - NuPrime (NuForce) Reference 20 Mono Block Amplifiers


May 13, 2015

It’s All About the Ears

It took me decades of trial and error, thousands upon thousands of dollars and countless hours of research to realize that above and beyond everything else, when it came to building the optimal audio system, I need to trust my own ears. 

I had completely bought into the popularly held notion that the more money I spent the better sounding my home audio experience would be. In this way of thinking money equated to quality. I was tantalized by enthusiastic write-ups and reviews that said I ‘needed’ to buy more expensive components, with more expensive wiring as well as all the associated accessories, paraphernalia, and fashionable bling and baubles.

At the time, I felt I was being a responsibly studious audiophile by educating myself about these seemingly miraculous components that were routinely lauded by the audio press and opinion leaders. And being someone who was sometimes a little overly curious, with definite obsessive leanings, I delved into the minutiae and what seemed to me like the increasingly mysterious black arts of audio-philia: resonance control devices, marker pens, elevating cables, power conditioning systems would be transformative to my audio experience – at least that’s the line I was being fed by salespeople and the audio press.

Clearly, I had become a devotee of the ‘Audio Illuminati’ – and most likely in need of a 12-step program for audio-gear addicts. My wife just thought I suffered from a mild emotional disorder that would go away in time.

For twenty years or more, my ‘collection’ of audio equipment grew because I had bought into the other popular notion propagated by audio magazines, columnists and other ‘experts’ that my system could always get better and that by ‘better’ they meant newer and more revolutionary. First came some mid-priced, solid-state components, a special CD player with a unique disc clamping system and some wonderful interconnects and speaker wires that the audio press guaranteed would change my life forever. Copper wires, silver wires and those made of ‘unobtainium’ all made brief stays in my world, while amplifiers and pre-amps flowed like spawning salmon through my audio bunker: all manner of solid-state, triode OTL, single-ended triodes, high-wattage KT 88 amps and a plethora of 300B amps continue to spawn vivid acoustic memories.

It seemed that the sonic beast that I had become always needed feeding. Fortunately, all was not lost and I managed to drag myself out of the morass of advertising hoopla, boosterism and the incessant drive to get my hands on whatever the opinion leaders in the audiophile media universe celebrated. After great expense, I regained most of my discriminating objectivity and was able to reflect on some hard lessons learned from my exercise of rampant consumerism. Most significantly, I learned that one should never believe all the magazine reviews and advertising hype – that the number one thing for experienced audiophiles to do is to trust their own ears.

Here’s one example that taught me a lesson I won’t soon forget, and I hope that by you reading this, you won’t leap headlong into the same predicament that I found myself in. I once spent $10,000 on a ‘previously enjoyed’ SACD/CD player that originally retailed for $20,000. Needless to say, I thought I was getting a bargain. Several audio magazines had reviewed it and claimed that it produced the best SACD sound they had ever heard. I played it and concurred with the reviewers one hundred per cent.

Unfortunately it only played 80 per cent of my SACD collection – disappointing to say the least. The other discs were rejected. I was a little puzzled and rather annoyed that none of the reviewers had mentioned this problem, nor had they commented on the sound quality of regular CDs when played through this device. When I played my regular CDs, the sound was bleached, dry and was without doubt, inferior sounding to any other player I had ever heard. When I contacted the company, they blamed the rejection of discs on the disc manufacturers themselves, In terms of the brutal sound when playing regular CDs – well they had no idea what I was talking about. The unit was sold and out of my house within a matter of days.

To this day I steadfastly believe that there is a far too cozy, symbiotic relationship between audio manufacturers and the so-called audio press. These large corporate entities dump boatloads of advertising dollars into these various print and online media outlets, with the unspoken (although often it is spoken) expectation of a favorable review. The combination of the slick, attractive, attention grabbing ad, coupled with a positive review from an allegedly impartial publication gives the product credibility within the consumer market. The publications benefit from the increased revenue and other perks (free merchandise and swag) and everybody is happy – except for the poor purchaser of that product who is buying something that may indeed be good, but perhaps not as good as advertised. Negative reviews are rare and if they occur are usually full of qualifications.

That is why we have a ‘hobby’ where one might invest $50,000 on a turntable and interconnects, and then an additional $5,000 on speaker wires. The collusion between the product manufacturers, marketing hot shots, retailers and audio media means prices for ‘premium’ components stay high, and each year we are told we ‘need’ to have the latest and greatest ‘thingamajig’ or we’re cheating ourselves of the best possible sound.

What does all this mean? I feel we need to be more discriminating in terms of the information on which we base our purchasing decisions. There is always going to be some validity and informative aspects of the audio media and audiophile bloggers’ opinions on products, so don’t discount them entirely. But as with any significant capital investment, cast your net wider: talk to trusted friends. Honest pals (obviously ones who are also audiophiles) would never steer you wrong and would never allow you to do something stupid or wasteful. The final arbiter, after weighing all the evidence and opinion should still be two key parts of your body – your gut and your ears. Trust them both.

So based on my enthusiastic but somewhat checkered search for audio excellence, I managed to learn this lesson and take it to heart. Now I work diligently to pass it on to my fellow audiophiles.

What I also learned, again often the hard way, was that most of my sonic issues and challenges had more to do with my listening environment than with the components and gear I spent my retirement savings on. Changing speakers, the positioning of the speakers and my actual listening position within my music room were far more impactful. This was the ‘ah-ha’ moment in my journey as an obsessive audiophile. More often than not, it’s the room, not the gear that is the primary variable in achieving the optimal sound you seek.

Getting back to our pals writing for magazines, blogs and online audio media journals, they almost unanimously will encourage you to buy more ‘stuff’ and/or pump up the power. Rarely, if ever, do they advise you to do a frequency scan of your listening room and address the fundamentals of sound engineering and physics. That’s what I will talk about in my next blog posting, as I use my own journey to help others make the best sound decisions. All the high-end components and most technologically advanced systems won’t make up for a room that’s not built for sound.

A Room With A View For Sound

In this second installment of a three-part blog, I will talk about the experience in designing and building my dream listening room. The rationale as to why you should build a room may not seem apparent at first, but stay with me and you will see there is a method to my madness.

And it is not something to be entered into lightly - it is a formidable process, costs a good deal, and will give you a taste for all kinds of dust and dirt. Fortunately my wife was completely supportive of the idea and this support made the job a great deal easier.

As dedicated audiophiles, you need to ask yourself what you would do if you found yourself without a high-quality, dedicated room for your listening enjoyment. Of course you would continue to listen to music in your current environment, but you would be doing so in a room filled with undiagnosed sonic anomalies. Bass booms, frequency suck-outs, echoes, frequency spikes would all be present in one form or another and to varying degrees. The detail and beauty of the music would be obscured by all these sonic interactions. Your ears would tell you something is wrong.

You would probably then start testing various wires and components to change the sonic landscape in the hopes of arriving at a listenable experience that might correct some of these problems, while creating new ones at the same time – very much like the little Dutch boy sticking his fingers into an increasing number of holes in a dyke. That is exactly what I did for many years, and that is the foundation of audio consumerism. None of the components and wires you buy will deal with the underlying problems. Worse than all of this, your ears and your brain will get accustomed to the colorations and anomalies in the sound and think it is normal.

Lesson: Creating a good listening room – one that is the appropriate size and outfitted with the right treatments will deliver wonderful sound. It will also mean you become less inclined to continually tweak the sound of the system with expensive components and wires. It will also provide a platform to more accurately compare and evaluate the things you put into your audio system. 

In early 2012, my wife and I decided to leave the open spaces of the countryside and construct a home in a more urban setting. It was a 2,000-square-foot bungalow with a basement that had the same size of footprint. As well, the basement was built to be a little over nine feet high from concrete slab to rafters.

Size

    The design of any listening room is an exercise in the physics of sound, so I examined all the suggestions that I could find from audio experts in room design and treatments (with many thanks to acoustical engineer Chris Huston). In determining the size of the room, I wanted it to be large enough to comfortably host a listening group of up to six – friends and fellow audiophiles with whom I have shared music for more than 20 years.

    Room dimensions for premium audio listening have been scientifically examined at the Acoustics Department of Salford University in the United Kingdom. They’ve determined through mathematical analysis that a primary design parameter is to select a set of room dimensions that minimizes resonances (primary, oblique and tangential). The bright minds at Salford have published their findings in spreadsheet form that has made the job relatively easy for the hobbyist. If you go to the following URL you will find links to the “best room ratios” and “second best room ratios”: Salford University

    If you download the spreadsheets, you will notice that the ratios are grouped in tabs according to room volume. There are ratios for rooms with a volume of 50 cubic meters, 100 cubic meters and 200 cubic meters (which is humungous). One observation stands out clearly – the larger the room the more ratios there are. Conversely, the smaller the room the fewer good ratios there are. This is why moving a speaker location a few inches in a small room may have considerable sonic impact. Small rooms are inherently more difficult to tune. All of this eye-opening research reinforced my plan to build a reasonably large room.

    My feeling has always been that a larger room is able to host more listeners, is easier to tune (with treatments), and allows the audio output to go deeper into the bass frequencies. And on a less technical note, I wanted a big room because I love how large orchestral works sound in an environment such as this and find listening to them – and music in general - with a group is a rewarding social experience.

    In my case, I chose from the list of “second best room ratios” owing to a structural column that interfered in getting enough width to use the “best ratios.” In the end, the internal dimensions of the room are 8 feet 8 inches (height), 16 feet 5 ½ inches (width) and 28 feet 9 inches (length). I admit that the room is quite large. The actual volume of the room is 4112.8 cubic feet. That translates to 116.4 cubic meters.

    Lesson: Build as large a listening room as the space, your budget and common sense will allow.

    Construction

      The concrete floors were covered with a hard plastic membrane to drain away any condensation and create a vapor barrier between the finished floor and the concrete. A layer of 3/8” plywood was then screwed into the membrane and concrete. A very solid hardwood floor was then installed after the walls and ceilings were finished.

      All cavities behind the walls were filled with acoustic insulation. All pipes, beams and vents were covered with an acoustic film that absorbs vibrations. Wiring was direct to the home’s main electrical panel via dedicated lines, and the entire panel is surge protected. The first layer of drywall (plasterboard) was 5/8” thick, and was a dense concrete product: the kind normally used in bathrooms. It was covered with acoustic glue and a second layer of drywall at 3/8” was then attached to the first layer. All cavities around electric switches, and any other gaps, were then sealed with acoustic foam. 

      The ceilings were finished exactly like the walls, meaning the final structure of the room is very rigid. This rigidity is extremely helpful in ensuring there are firm delineated bass frequencies and wonderful decays. Walls that are not rigid will, under acoustic loading, reinforce a loose, woolly sounding bass and obscure detail in higher frequencies. I thought about de-coupling the wall structure and decided it was unnecessarily expensive and might interfere with bass management. I also gave consideration to building double walls with an air gap so that my wife would be completely undisturbed by any music. Unfortunately the cost and other practical construction issues nixed that idea. But I am still incredibly happy with the result.

      Lesson: Do not skimp on construction materials or design.  Make the room rigid. Try and stay within a budget. Get used to living in drywall and plaster dust for a while – the result will be worth it.

      Treatments

      All the treatments in my room were designed by Chris Huston and installed in the manner that he advised. Virtually all the treatments were acquired second hand from reliable used and after-market sources. I owe a debt of gratitude to Rick Hopkins who was my hook-up for these products as he had hired Chris to develop a new personal listening studio for himself at around the same time. 

      There is a pair of bass corner traps on the front wall. Each is a framed triangular structure with 3/8 inch plywood top and bottom and on two sides. The cavity facing the room is stuffed with acoustic material and covered with material from a roll of swimming pool liner. This material reflects high frequencies while allowing bass frequencies to pass into the trap. The pool liner is covered with an acoustic fabric.

      There are a total of 12 slotted, barrel-shaped diffusers on the side walls. These were installed as close as possible to the center of the room. The acoustic nodes are strongest in the center of the room. A small ceiling drop and small columns left and right in the center of the room also helps to break up any remaining standing waves. Acoustic absorption panels were installed in the very middle of the room and immediately after the diffusers. Absorption panels were additionally installed at the back of the room to remove traces of an echo. Finally, furniture was specifically ordered for the room and this provides additional absorption. These touches included six comfortable armchairs and a 10-foot by 12-foot Persian rug.

      I could have installed diffusing treatments over the listening position and I also could have installed a rounded front wall to serve as a barrel diffuser. Both are still possible and I may investigate these options in future. For now, the results have been hugely successful and the room sounds simply stunning.

      Lesson: Treatment applications should be done in a scientific manner and kept to a minimum, as over-treated rooms can sound dead. Careful, incremental additions over time work effectively at arriving at the perfect balance. Seek out used treatment products as they work as well as brand new ones. Above all else, if possible, ask an expert like Chris to help guide you trough the process. 

      I’ve told you about the room and in the next installment I will discuss the gear I have installed, why I chose the components and apparatus that I did, and my newly found love for the digital world.

      The Goods and The Gear

      This is third installment in my ‘Audio Odyssey,’ where I will discuss the equipment that I chose to evaluate and eventually use in my finished audio room retreat.

      The Speaker

      The most important piece of equipment in a room is the speaker. Its interaction with the room is the most significant part of the listening experience. I built a large room primarily because I like listening to recordings of large orchestral ensembles and I wanted a good sense of scale in my sonic environment. This choice would necessitate the acquisition of a full-range speaker.

      Over the years, at homes, audio shows and dealerships (a threatened species), I’ve heard a wide variety of full-range speakers. I’ve owned and listened to such transducers as the Coincident Total Eclipse, Super Eclipse, as well as their Total Victory. I’ve heard an assortment of speakers from Gallo, Harbeth and Sound Labs. At audio shows I have been very impressed with Magico products and horn speakers by Avant Garde. I’ve listened to Wilson speakers and those by B&W, MBL, Quad and a host of others too numerous to mention. So I can confidently say that I have done the rounds and paid my dues.

      Of course, the cost of speakers is an important consideration in this hobby. The unfortunate truth is that it seems one would need far in excess of $25,000 to put together a good sounding full-range audio system (speakers, electronics and wiring). For a so-called ‘statement’ product you could spend many multiples of that number on the speaker alone. For me, the question was how much system I can get for my hard-earned dollars. Having heard scores of speakers in my life I developed very specific criteria to determine my options.

      I wanted a speaker that was efficient, easy to drive, with a benign impedance curve and with a full-range frequency response.

      I’ve had many opportunities over the last 10 to15 years to listen to audio products in the home of a local audio manufacturer. His well-known line of expensive statement products includes mono block amps costing near $30,000 and a statement preamp in the vicinity of $8,000 (perhaps a bargain by audiophile standards). While he has changed speakers every now and then, one pair of speakers has been a constant - Canadian-made Tannoy Churchill. I believe about 50 pairs of the original model, with an external crossover, were made before production ceased (sometime after 2000).

      The Churchill’s woodwork is elegant and the sound is sumptuous. The design of the drivers is coincident with the tweeter inside the woofer. Listening to such a speaker is easier on the brain, as it does not have to integrate the sounds coming from many different arrays of drivers into music. The sound is coherent, impactful and richly detailed. It is 94db efficient, and its impedance curve is benign. Its 15 bass driver and large magnet structure can truly plumb the depths of the bottom frequencies. Fortunately for me, one pair came up for sale shortly after my room was finished, and as you can see they now grace my room. It’s great to get lucky!

      Lesson: The speaker is the most important element of your audio system. If you find out what the speaker of your dreams is, seek it out and purchase it. If your budget is tight, consider buying a used pair in very good condition.

      The Amplifiers

      As I stated in Part 1 of this article, over the past 25 years I have experimented with a variety of amplifiers – everything from solid state, OTL, push-pull designs and single-ended designs. Over the last decade, my reference design was a 50-watt, push/pull pair of 300B mono blocks. My ears were used to the sweet velvety mid-range with a roll off in both the high frequencies and the bass. It was a good compromise in an audio room that was by and large untreated.

      On my way to owning my current speakers, I picked up a pair of rather abused Tannoy Ardens. They too have a coincident design with a 15-inch woofer. I completely rebuilt and refinished them and was surprised how musical and coherent they sounded. Naturally there were some issues with cabinet resonances and their ancient crossover design. Given the 15-inch woofer, I thought a solid-state amplifier might prove beneficial with its high damping value (high current to control the movement of the woofer). A close friend, who had a 500-watt Class D amplifier, suggested I compare it against my 300B mono blocks. My 300B amps cost six times the price of this Class D amp. For my part, I expected a resounding tube amp victory over the solid-state design.

      Instead, to my complete amazement there ended up being no comparison. The Class D amp was very smooth in the high frequencies, yet its mid-range had greater detail and delicacy. The bass was impactful and well delineated and better extended. Yes, the digital switching amp, with its damping factor over 1000, was more capable of controlling the woofer than a 300B amp, with a damping factor of about six. The inability of the 300B amp to control the woofer created a number of artifacts that obscured mid-range details and bloated bass frequencies.

      After my room was built I eventually tried the NuForce* Reference 20 mono blocks. It is without doubt the most musical, detailed and impactful amplifier I have ever listened to. Its performance is absolutely statement level. Its control over the Tannoy woofer is astounding and I’ve yet to hear a better combination of speaker and amplifier. I’ve listened to countless amps these last 20 years and this one is simply the crème de la crème of amplifiers. But this shouldn’t have surprised me. A growing number of audio hobbyists and magazine reviewers had declared that its predecessor, the NuForce Reference 18, was a statement product and you should have a listen if you were interested in a true reference amplifier. For once I had to agree with the audio press, as confirmed by my own extended listening.

      A highly-regarded tube amp/preamp manufacturer, and the maker of equipment that had seen much positive press from The Absolute Sound, came by for a listen. His first response was, “Are you trying to put me out of business?” “Class D amps have finally arrived,” I replied, with a smile. I think his comment was really an acknowledgment of my well-designed listening room.

      Lesson: Class D amp technology has matured over the last decade, so you have to consider it. It offers incredible power, great musicality, and runs completely cool. It seems to offer the best attributes of solid state and tube technologies without any of the drawbacks. Several amp manufacturers are now moving into the design and production of these amplifiers.

      The CD Player

      The center of my digital system for about 10 years was a highly regarded, high-end SACD/CD universal player from an American company of some note. It cost me in excess of $6,000 new, and it was a recommended Class A component in Stereophile for many years. Prior to my room being built, I gave serious thought to replacing it with an Oppo 105 ($1,200). Don’t laugh! In a head-to-head comparison, everyone in my listening group preferred the Oppo. It had better pace, detail, and more realistic tonality. It sounded more musical. Furthermore its architecture made for a computer audio application (more on this later in this blog entry). This was something my legacy universal player could never do. Since then, several members of my listening groups have acquired the Oppo 105. Keeping an older high-end, expensive, legacy CD player makes little sense owing to the widespread use of the 32 bit Sabre chip in newer digital products. In the simplest of terms, older custom CD players have been rendered obsolete by improvements in chip technology.

      Lesson: Digital technologies develop and mature and make possible high-end performance at far reduced prices. Never discount a product because it doesn’t cost enough. Remember what I said back in Part one of this three-part blog – a higher price doesn’t necessarily equate to a better product. Trust your ears.

      The Pre-amp

      Throughout the twists and turns of my sonic journey I have used a number of pre-amplifiers, but in recent years I settled down with a fully balanced tube product. It cost a little more than $6,000. Again, it was Class A in the audio press and highly regarded. After my room was in operation with the Oppo 105, someone challenged me to use the volume control in the Oppo. He reasoned that as the Sabre chip is 32 bit, I could adjust volume over a 120db range without reducing resolution beyond 24 bits. That offered complete control with no loss of resolution, even on high-resolution computer files. Considering that no component, including my preamp, is perfect and eliminating interconnects could only be beneficial, I did the comparison. It took me one song lasting five minutes to determine that this was correct, and then two days to sell off my preamp. This relatively simple test has resulted in a system that sounds more musical, is more detailed, and has less artificial colorations.

      Computer Audio

      So I’ve now arrived at a music system that has a source component that plays discs of every kind. I had to ask myself whether I really wanted to spin discs at all. Computer audio offers the convenience of rapidly accessing your music and playing it with the ability to correct for any of the aforementioned residual system or room issues. I began collecting music on my iMac over a year ago. Auditioning computer audio through a friend’s system convinced me that was the path to further utility and simplicity. When I play a computer audio file with Amarra Symphony or Pure Music, I can make corrections to the digital data stream and obtain the ultimate in musicality, correcting for any residual room or equipment issues. One can optimize for a single listener or for a room full of people. I’ve stopped spinning discs. I’ve never enjoyed music more than this, and I’m listening every day. While I thoroughly enjoy the sound of Amarra, the facility and ease of Pure Music and its rich set of features (channel balance, phase inversion, mono blending) are very hard to resist. Both applications work seamlessly with iTunes.

      Wires

      Having simplified my system significantly in recent years, I decided to try inexpensive wires. Guess what? I now use a balanced Mogami interconnect between my Oppo 105 and my NuForce* Reference 20 amps. My Mac Mini is connected to my DAC with a Chord Company USB cable. My speaker wire is an inexpensive cable once made by NuForce*. All these wires together cost me less than $450. I’ve kept my audiophile reference power cords (Silent Source) because everything sounds more musical to my ears when they power my components. Why power cords can make such a difference is beyond me, but it is a distinction that is clearly audible to everyone who hears it.

      Lesson: If you build a good room and correct for all system and room issues, you don’t need to use expensive tone controls, which are what audio cables (interconnects and speaker wires) really are – especially the mega-expensive ones.

      Cost

      Naturally, all this gear was going to cost some hard earned dollars. So lets tally up the approximate costs ($USD) and balance that cost with money realized from the resale of the older equipment.

      As you can see from the table that follows, for a net cost of less than $4,600.00, I finally have an audio system that I don’t feel compelled to change. The room, of course, has a great deal to do with that state of finality and contentment. Most importantly, I explore a musical database and listen to music almost daily.

      Speakers Used Tannoy Churchills $6,000.00
      Amplifiers NuForce Reference 20 monoblocks $7,600.00
      Digital Oppo 105 $1,299.00
      Computer Mac Mini and screen $950.00
      Wiring USB, Mogami Interconnect, Nuforce speaker wire $450.00
      Software Amarra; Pure Music $775.00
      Total Cost New Audio Equipment $17,074.00 
      Less the sale of older audio equipment no longer required $12,500.00
      Net Cost $4,574.00

      Conclusion

      Now I’m at a point where I have the most minimal audio system I have ever owned. I am also proud to say that it’s also the most musical system I’ve ever had. The architecture is incredibly simple. My computer sends a corrected digital stream to a DAC, which converts the signal and transmits it to my digital amps that are connected to my Tannoys.

      Lesson: A pretty smart fellow named Albert Einstein once said this: “Make everything as simple as possible, but not simpler.”

      I couldn’t agree more, and I hope you will learn this yourself in your own audio odyssey.

      Please Note: *NuForce Reference is now owned by NuPrime Audio

      For more information on the NuForce Reference 20: Read

      - BILL KRAUSE


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