Car analogies are not always the best choice when discussing audio equipment. But I can't help think that in a broad sense, owning a great solid-state amplifier is not unlike owning a high-performance sports car, in that you are intentionally paying for an excess of capability that you will not use on a daily basis. But, because of your enthusiast-level interest, you want that capability for those times when you are able to experience—and enjoy—the full measure of what the car, or in this case the amplifier offers. And in that context, reviewing the Classé Delta Stereo amplifier ($12,999) is very much like spending quality time with an exotic supercar, alternating between driving it on a test track and through twisty mountain roads.
This review is the result of the simple request, which is for an amplifier that is of suitable quality to accompany a pair of Bowers and Wilkins 805 D4 bookshelf speakers that are the subject of a forthcoming review. Don't let the "bookshelf" designation fool you, the speakers offer an anechoic response of 42 Hz to 20 kHz, +/-3 dB. The only catch is that like other bookshelf speakers, the 88 dB sensitivity rating is notably lower than you find with tower speakers (physics being a law and all that). Paradoxically, having plenty of power on tap for handling dynamic peaks is more important than would be the case with larger but more efficient speakers, as long as the bookshelf system can handle it, because you need more watts to get to the same output level.
Unquestionably, this review system is a top-tier amplifier and speaker combination delivering the audio equivalent of supercar performance. It's no surprise you'll find the combination of Bowers and Wilkins speakers and Classé amplification in Abbey Road studios, which may be famous for the music to come out of its various rooms, but these days is also creating some of the top soundtracks for blockbuster movies. You may not know it, but you have many times heard amazing sounding material that was mastered on a combination of Classé and Bower & Wilkins.
The 250 W/channel (8 ohms) / 500 W/channel (4 ohms) of power created by this amplifier is more than enough to drive many speakers to their full potential, but it doesn't hurt having reserves to handle transient peaks found in high dynamic range recordings, whether it's music or AV applications where speakers have to deal with sound effects like explosions and gunshots, effects that only sound realistic when reproduced with proper intensity.
Equally importantly, this amp operates in pure class A mode for the first 12.5 watts for each channel and provides VU meters, so you can see if you are exceeding that threshold—or with casual listening, how surprisingly far you are from even reaching it. You'd be surprised how much sound you get out of 12.5 watts, even with 88 dB sensitivity speakers.
Inside, you'll find a custom-made toroidal transformer, hand-laid 6-layer circuit boards that the company credits with lowering noise and shortening signal paths. Premium components include a total of 22 4-pole Mundorf capacitors that allow this amplifier to take "sips" of power from the outlet as needed while ensuring ample reserves in case things get serious quickly. It has custom Navcom vibration-absorbing feet, and rhodium-plated Furutech RCA terminals and speaker connectors. All this is contained in a 17.50" x 19.37" x 8.74" (W/D/H) chassis weighing in at 102.3 pounds.
Click here to see full specifications for the Delta Stereo amplifier.
I'm a bit of an opportunist when it comes to living the #audiophilelifestyle and writing reviews, so I used the amplifier with more than just the Bowers & Wilkins 805 D4 speakers. I also have a pair of Focal Aria K2 936 towers, just recently reviewed, which are rated to handle up to 300 W of power and which are a great match for this amplifier. But that's not all! As a matter of opportune timing, I happened to have a pair of the updated KLH Model 5 speakers in for review, a three-way acoustic suspension design with a 10-inch woofer and 200 W RMS power handling (800 W peak, says KLH) that's at once retro in looks and form factor, and up to date in terms of the drivers and crossover.
Three distinctly different speakers, one great amplifier. What more could I ask for! Well, a source or two and some sort of preamp, maybe a DAC? No problem, I've got all that: Check out our review of the Motu M4 4X4 USB audio interface to see how I solved connection issues and put together a minimalist system featuring all balanced XLR connections. I even included a CD player in the mix, because concurrent to the amp and speaker reviews, I also wrote up the new Rotel flagship RCD-1572MKII player.
If you sense an ongoing theme here, that the amp is the one constant in these reviews, let me tell you this... it's not out of vanity. While I love a piece of top-tier gear, the main reason I did not swap the amp out is the most basic of physics: I can't easily move it around on my own. So after my wife helped me get it into place after it arrived, that amp became my source of power for everything I listened to.
I suppose the only appropriate term for how the Classé Delta Stereo performed in my system is "perfectly." A perfect performance, like a perfect 10 in the Olympics. What else can I even say? Anything that would distort, diminish or detract from music, movies, or video game sound, is pushed so far away from the threshold of human perception, it's almost comical. The capability is such overkill, it's almost comical: The rated response of 1 Hz to 650,000 Hz encompasses everything from Elephant infrasound communication (12 Hz) to bat calls (up to 200 kHz), and beyond!
I spoke to Classé about the design philosophy behind the amp, which is designed to operate in pure class A mode up to 12.5W per channel, while providing huge class A/B power reserves—all wrapped up in a massive, rock-solid chassis that's designed for optimal fan-assisted cooling. A fan? Yes, we're going to talk about the fact there is a fan in this amplifier, and why that's a good thing! Because whether you are building an amplifier or a space telescope when it comes to getting exquisitely engineered electronics to perform at their peak, precise temperature regulation is the key to achieving maximum resolution.
With the Delta Stereo, Classé carefully modulates airflow to achieve a precise and stable internal temperature, that it then maintains regardless of output level. The entire amp remains temperature-stable through its operation, and the simple fact is this is not possible without active cooling.
Active cooling presents another distinct advantage for this Classé amp, it allows for rack mounting. If you put together a cost-no-object home theater you can use a stack of Delta Stereo amps in a rack and not have to worry about thermal issues.
In a typical audio review, this is the point where I would veer off into describing how various tracks sound. But first, let me qualify by saying that when I do that for this amplifier, what I'm really describing is everything else. The recording itself, the quality of the source, the speakers, and how my room interacts with the sound coming out of those speakers. Because in this equation, the amplifier itself is invisible. It doesn't exist. There is no character to describe other than its transparency, no warm or cool or smoothness or harshness. Those qualities would imply the amplifier is changing the signal, which it absolutely is not, it is keeping things ruler flat and free of audible distortion way beyond the limits of human hearing.
What impresses is the Delta Stereo's ability to drive any of the speakers that I connected to it—to their limits—without reaching its limits.
The payoff for this clarity and neutrality is the ability to get the maximum performance out of a given system. To achieve the sublime where the components effectively vanish, leaving the music hanging in the air before you. Each element is distinct and to proper scale, with vocals especially coming through photographically. It is a tangible illusion that is only contradicted by what your eyes see, which is that you are listening to a stereo system.
As I said in the review of the Focal Aria K2 936 tower speakers:
"It revealed every layer within the mix with a clarity that allows it to expand in three dimensions and render the system itself "invisible" the speakers are not localizable because the soundfield is 100% cohesive. And even in stereo, this system can place sounds seemingly anywhere, even behind your head, if the sound engineer knows how to manipulate phase to achieve the effect."
Close your eyes and the dissonance disappears. You are no longer listening to gear, you are listening to the artist, and the illusion of being in another space is the oldest form of virtual reality that AV technology provides, and it is now perfected to a point where a great system will transport you right to the location of the performance—or for a studio album, you can explore the layers of a sophisticated mix and discover new nuances even in familiar tracks. The point is, a great system's fidelity will lead to suspension of disbelief, and that profound feeling you get when you lose yourself in the music.
The Bowers and Wilkins 805 D4 speakers that are the very reason I have the Classé Delta Stereo in hand are thus far the finest bookshelf speakers I have had the pleasure to hear in my home, and what I got out of them is a textbook performance that transcends measurements and specifications and components. It is holistic synergy at work, like a great quarterback and receiver who work together to bring home multiple Super Bowl trophies, the amp passes the signal (ball) with utmost accuracy and power, and the speakers score the touchdowns. As I type this I'm playing the classic album Gorrilaz - Plastic Beach and it is absolutely bumpin' through this rig, and you can bet Snoop always uses a quality microphone in the studio, right? Just sayin'.
When I queue up albums that I know to possess excellent production value, the jaw-dropper is the absoluteness of separation between the physical presence of the speakers and the soundfield. With eyes open, I can try as hard as possible to outthink the illusion—to somehow localize the speaker—and it's simply not possible. Beautiful sound just flows out of this awesome amp, there's no other way to put it.
The KLH Model 5 speakers I reviewed are the most affordable pair I reviewed using the Delta Stereo amp, but no less deserving than the others. They are a 3-way acoustic suspension speaker with a "classic" cabinet design resembling giant bookshelf speakers, tilted upward on their stands. The sealed enclosure and large woofer appreciate some juice, and the drivers used in this model are robust modern components that appreciate a good amp. To quote from that review:
I fed them the Cowboy Junkies' cover of "Sweet Jane" from The Trinity Sessions, a track that impressed me back in the day when I was first getting serious about high-fidelity sound. It's a gorgeous recording made with a single microphone in a church, and I now have 30+ years of experience listening to with every system I've owned. And here's the contradiction… a "classic" speaker delivers one of the best renditions I've heard of the track, which depends so strongly on getting the basics right, vocals, drums, acoustic guitar, and the ambiance of the space captured in a live recording. Every time lead singer Margo Timmins says "sweet" a lesser speaker will cause a slight wince from sibilance, but the tuning of the KLH is such that it registers as it should, momentarily sharp in tone, with a clear emphasis not found in the pronunciation of letter s in other words in the track, but also not exaggerated or artificial.
The point is the speakers in these reviews are beneficiaries of the amplifier's generosity. I did not have to worry for one second about power. I'd need to find it much harder to drive speakers to possibly challenge its supremacy over the rest of my system. Simply put, Classé Delta Stereo is the boss.
In my listening room which is 17' x 26' x 11', I do not need all the power this amp provides to enjoy a spirited performance. Much of the time the meters stayed well below the 12.5-watt threshold where the amp switches to class A/B, and when it does quite frankly I cannot tell a difference, but I certainly understand on a technical level why class A is the preferred amplifier topology of audiophiles, since it follows the KISS principle coined in the U.S. Navy by aircraft engineer Kelly Johnson.
I don't need a space heater in my living room, which is the flaw of class A amps, they constantly eat up current and turn it into heat. The thing is class A amps consume power at a constant rate, which in turn means they run at a constant temperature, so that aspect of stability is inherent to their design (presuming adequate ventilation and typical room temperatures). The Delta Stereo consumes approximately 300 watts continuously—under most circumstances. If you push it, you'll start to see it gulp down the extra amperage it needs in chunks, quickly refilling its power reserves. That 300 watts on continuous draw provide enough current to warm things up inside the amp and give the active cooling something to work with, plus deliver the pure class A operation.
Of course, the speakers get credit for doing what they do, converting current into sound waves, but without the amplifier as a willing partner—one that is free of dynamic compression and distortion—you won't get the same degree of immersion.
If you put visuals up on a screen, you no longer need to close your eyes to forget where you are. Modern home theater plays in the big leaguers when it comes to audio, and quite frankly the demands on a home theater system playing back a movie with a dynamic soundtrack can exceed those of 2-channel sound. For one, the use of hi-res sound is practically a given with Ultra HD Blu-rays, and the dynamic range involved in reproducing an action sequence—one that includes gunshots and explosions—is enough to test the mettle of any amplifier.
Oh, speaking of studios and mastering, I like to dabble in music creation. Sometimes it's just soundtrack music for videos, but other times it's a creative exploration of digital music creation and I'm making real standalone compositions. Digital audio workstation (DAW) software is amazingly sophisticated—a sampled orchestra can take up a terabyte of space—and many have heard of ProTools due to its use in studios (like Abbey Road). But the heavy lifting is often done by plug-ins such as virtual synthesizers and sampled instruments.
The point is, you can put together studio-quality tracks and master them properly if you have a good system you can rely upon. And what's better than having the same sort of system that's used by the world's most famous studio? You already know the answer... there's nothing better. And the reason this matters is that during the creation process, you are dialing in levels and also dynamic compression and panning and reverb, echo, etc. You want to hear the subtle changes, how elements sit in the mix. It's an absolute trip to load up a virtual synthesizer and just start playing with presets, feeding 24-bit 192-kHz data directly to the Motu M4, which translates it directly into a balanced signal it sends to the amp.
There's practically nothing between the synth and the speakers, and the soundscape explorations are at times as much fun to "hear" as listening to fully composed music. Load up a drum machine and a bass synth, grab some hip-hop midi, and soon enough a groove is going... but it's pure hi-res, no dynamic compression, and tweakable. I'm not saying it's a drug, but it is addictive.
The Classé Delta Stereo amplifier exists in a rarefied realm of gear that is at once utterly excessive and yet not in any way frivolous. It is not afraid to do what it takes to achieve levels of performance that elude lesser amplifiers. It grabs the high-end by the horns and says: Hey, yes, there is a path forward in amplifier design wherein active cooling is used not merely to dissipate heat, but to keep electronics at an ideal temperature.
It is a cost-no-object purchase, I would not pretend otherwise. But, it is a wise cost-no-object purchase for anyone seeking a true endgame solid-state stereo amplifier and a definitive Editor's Choice winner for a high-end solid-state stereo amp that's perfectly suited for traditional stereo systems and use in a home theater context.