Starke Sound A2.640 Stereo Power Amplifier Review

Despite its 92-pound presence, the Starke Sound A2.640 power amplifier is the anthesis of slow and massive in its sound. Using fully balanced, differential circuitry, it is one of the most articulate and detailed amplifiers I’ve ever heard. Despite being a relative newcomer in the world of audio amplification, Starke Sound has clearly established their bona fides as a premiere maker of state-of-the-art power amplifiers. Whether or not you can afford one, should you ever get the chance, you should hear this amplifier!

I have an audio amigo who has always contended that, other things being more or less equal, more watts are ALWAYS better watts. I, however, have never been convinced. But maybe I’m going to have to rethink my position, at least in the case of the Starke Sound A2.640 power amplifier. Even though my (and your) typical listening level requires less than one watt, and even though almost all amplifiers have enough output bias to remain in Class A mode for that first watt, this Starke Sound A2.640 power amplifier offers control, detail, and sound staging beyond what I’ve heard before. Using a wide range of speakers on a wider range of music, I’ve concluded that this 640 WPC amplifier is the best I’ve heard.

And now for something completely different – the Starke Sound A2.640 power amplifier. One would expect a premiere product to provide outstanding performance, but the Starke Sound A2.640 is not just a premier product, but a pinnacle one! I had the pleasure of reviewing the Starke Sound AD.320 a while back and thought it was one of the best amplifiers I’d heard. A lot of readers accused me of hyperbole with that review, but the vast majority who actually auditioned that amplifier quickly and overwhelmingly agreed with me. In fact, many bought the AD.320 after hearing it. That amp is still my top recommendation for friends who ask for a power amplifier recommendation near the thousand-dollar range. I still wish I had it… So, if Starke Sound provides amazing performance at that price, what might they do for many times that design budget? Enquiring ears want to know…

• Starke Sound A8.350 Multichannel Power Amplifier Review
• Starke Sound AD4.320 Power Amplifier Review

Weighing but a trivial 92 pounds, the Starke Sound A2.640 power amplifier can be unpacked by one strong person. But due to this amplifier’s brutal size to density ratio, it is best handled by at least two people. Double-boxed, cushioned by full top and bottom Styrofoam plates, and wrapped in an elegant thick felt protector, the Starke A2.640 arrives with the full announcement of its premium product status.

WARNING: Most audio equipment racks, even a lot of expensive ones, are rated for no more than about 100 to 150 pounds. With most equipment, those limits are usually more than sufficient, but the Starke Sound A2.640 power amplifier is NOT “most equipment.” It will not be sufficiently ventilated by the normal 8-inch rack spacing, and its weight, alone, may cause some equipment racks to fail catastrophically. I wouldn’t try putting this amplifier on any glass-shelved equipment rack that I’ve seen. I’d also pause before trying to put a heavy flat-screen television on any equipment rack in conjunction with this amplifier. Do your research before putting this amplifier on any equipment rack. Please!

The Starke folks said that one of the design goals for this power amplifier was to provide top performance and power without the use of cooling fans. They have succeeded. Using the most massive aluminum heat sinks I’ve ever seen, the A2.640 not only lives up to my inherently high sonic expectations for a Starke Sound amplifier but does so without breaking a sweat. Using graphene as a heat-dissipation and conduction material, combined with the cast aluminum heat sinks, this amplifier runs coolly despite any load. To stress it, I tried wiring two pairs of four-ohm speakers in parallel, providing an approximately two-ohm load. The A2-640 didn’t even blink. In fact, the hottest temperature I ever recorded for the heat sinks, even at two ohms was 84˚F.

The interior of the Starke Sound A2.640 reveals the most robust construction I’ve ever seen in an audio component. This amp gets my vote as “most likely to survive Armageddon.” All components are of premium quality and the construction is robust, to put it mildly.

Starke Sound claims that the A2.640’s first 65 watts per channel are fully Class A. The definition of a Class A amplifier is one in which both output stages are constantly on at full power. Because of this, Class A is the least efficient design, with an average efficiency of about 20%, meaning the remaining 80% is lost to heat. The Starke Sound A2.640 power amplifier’s idle measurement, however, shows that the amplifier is consuming only 64-69 total watts at idle. This is not a true Class A amplifier.

The amplifier’s Class A operational envelope may be provided by a Class H style bias system. Class H amplifiers create a variable power supply rail, sometimes being referred to as rail trackers. This is done by modulating the supply rails so that the rails remain a few volts above the output signal, “tracking” it at any given time.

The Starke Sound’s bias system uses a two-level bias mode that increases bias current with signal demand. This is intended to provide the benefits of Class A operation but without the extra heat.

The output transistors (10 pairs of op-amps for close signal matching) can produce significantly more than 600 watts per channel with a peak output of 2,100 watts per channel! In standby, the A2.640’s 12-volt trigger circuitry consumes two watts.

Associated equipment used in this review:

• Mac mini running Roon with an external HDD music library
• Emotiva Big Ego DAC
• Alps Passive Volume Control / Emotiva PT-1 preamplifier / DAC digital volume
• Audioquest graphite interconnects
• RCA to XLR adapter interconnect cables used occasionally so that the balanced circuitry of the power amplifier could cancel hum and noise
• Straight Wire speaker cables (jumpered at the speaker terminals for speakers using bi-wire terminal sets)

Speakers used for audition included:

• Focal Aria K2 936 Special Edition
• Bowers & Wilkins 704 (original versions, not the S2 versions)
• Klipsch RP-600m bookshelf speakers with additional internal damping
• Harman-Kardon MKS bookshelf speakers with a subwoofer

To assess the bass performance of the Starke Sound A2.640 power amplifier, speakers were auditioned both with and without a subwoofer except for the HK bookshelf models. No bass management was used, so all speakers were run full range both with and without the subwoofer active.

The variety of speakers used displayed different aspects of the Starke Sound A2.640’s performance. Despite some humble origins, these speakers were selected for a specific reason – I’m intimately familiar with their sounds except for the Focals which have just arrived for review. That familiarity has been acquired in my room.

The differences due to the A2.640 were instantly audible. It should also be noted that I have a medium-sized listening room, and do not listen loudly. Although I wasn’t measuring, I’m confident that 90% of my auditioning was done at one watt or less. The peak levels of “turn it up” rock or bombastic classical scores might have consumed 10 watts.

The immediate question that will probably arise in the minds of readers is, “if you’re only using one to 10 watts, why would you even consider a 640-watt amplifier?” It’s a fair question and one that deserves to be answered.

If, for example, Starke Sound offered a 20 WPC amplifier voiced to sound like the A2.640, could I hear a difference? I actually think that I could, and the reason would have to do with the damping factor. Damping factor is defined as a ratio between the speaker’s impedance divided by the amplifier’s output impedance. As the number of amplifier output devices increases, the amplifier’s output impedance drops. Therefore, amplifiers with more output devices generally have higher damping factors.

Amplifiers with higher damping factors more tightly control a speaker’s drivers (particularly the woofer(s) where mass is higher, and ringing is more audible). Some amplifiers have low output impedances over only part of their frequency range, but the Starke Sound A2.640 power amplifier specifies its output impedance as <0.012 Ohms from 5 to 50kHz. This means that, even in the worst case, the A2.640 provides a damping factor of 333 for 4-ohm speaker impedances. This is excellent. In most cases, the damping factor will be significantly higher.

And is this audible? Oh my, yes! The Starke Sound A2.640 provided the tightest and most tuneful bass I’ve ever heard from my speakers. Cello music was visceral with the A2.640 and made the instruments more tactile sounding in my room than I’ve ever heard before. Would that all amplifiers could sound this great in the bass…

But the benefits of that damping factor don’t disappear once the music ascends from the lower octaves. In fact, if I had to describe the Starke Sound A2.640 in a single word, that word would be “articulate.” Now in some cases, “articulate” has been used by reviewers as a synonym for “forward,” or “bright.” That is NOT the case here. I heard no brightness or glare at all unless the speaker itself was inclined in that direction.

In fact, the Starke A2.640 is going to force me to use a cliché: I heard things in familiar recordings that I’ve not heard before. There – I said it. And in this case, it’s true. The midrange, where the music is, seemed more like real voices and instruments in real space than with any other amp I’ve heard. The amplifiers that I found to be the closest in verisimilitude is my pair of 12-watt Heathkit custom tube monoblocks. Of course, the Heathkits don’t compete in the bass or ultimate loudness, but in the midrange, they’re awfully close.

Don’t think that all this detail comes at the expense of harmonic information, either. The Starke Sound A2.640 is not a dry-sounding amplifier at all. The realistic detail allows the listener to hear deeper into the recording than I’ve experienced before. I think that this is an artifact of the excellent damping factor combined with exceptionally low inter-channel crosstalk, but that is speculation on my part.

With less than great recordings, that insight into the midrange hides no recording flaws at all. But even with poor recordings, the amplifier seems to make the best of whatever you feed it. Ultimately, and for whatever reason, the midrange of the A2.640 is ravishing, in my opinion.

The treble of the Starke A2.640 power amplifier is transparent enough to avoid calling attention to itself. There are no sibilance issues, and the high-frequency extension is outstanding. If the speaker can get the treble right, the amplifier will not stand in the way.

What about sound staging? The Starke Sound A2.640 excelled at both center depth and at presenting images not just outside the plane of the loudspeakers, but FAR outside the physical speaker locations.

Some prime examples would be “Soy Yo” by Bomba Estéreo and “Vogue” by Madonna (from the “Immaculate Collection” CD). In Soy Yo, there are drums that are out of phase and appear to come from both sides of the listener, and I mean truly at 90 degrees from the plane of the speakers. In Vogue, a spatially processed recording using Q-sound, voices, instruments, and other effects should be heard not only from the sides of the listener but almost, in some instances, from behind the listener. Now reproduction of these effects depends strongly on:

• The use of speakers that can create a smooth midrange frequency response
• A room environment that is symmetrical from side to side
• At least adequate reflection control and/or room damping

But if those conditions are met, the Starke Sound A2.640 vividly delivers a holographic sound stage that is one of the very best I’ve heard.

To tax the A2.640 power amplifier without exceeding the OSHA noise limit, I wired the outside and inside speakers in the photo below in parallel. I emphatically do not recommend you try this unless your amplifier is rated for 2-ohm loads and even then, with some trepidation. Nominal 4-ohm impedance speakers can sometimes dip to 3-ohms or less. Should such speakers be wired in parallel, the impedance could be as low as 1.5 ohms at some frequencies. The manufacturer of your amplifier will NOT honor the amplifier’s warranty if you burn it up from an excessively low impedance load.

I braved the experiment not only because the Starke Sound A2.640 power amplifier is rated for 2-ohm loads, but also because the speakers being wired in parallel were not identical makes and models (and thus, were highly unlikely to have impedance dips at the same frequencies).

The result, with the outer speakers, toed-in slightly and the inner speakers (surprise!) toed-out slightly, was the most realistic presentation of an orchestra that I’d ever heard in my listening room. Width, depth, and detail – it was all there. I was surprised. I was even more surprised to note that the A2.640 power amplifier when powering TWO four-ohm speakers per channel, neither ran any hotter nor drew any more wattage than when driving a single speaker.

My conclusion is that the Starke Sound A2.640 power amplifier was just loafing, even with a 2-ohm load on each channel. This speaks well of the amplifier’s ability to tolerate abuse, provide a long service life, and sound good while doing it.

The Focal signature K2 936 models are rated at 4-ohms and are a three-way tower speaker with three woofers, a Kevlar© sandwich midrange cone, and an aluminum/beryllium inverted tweeter (review to come). Their -3dB point in the bass is about 40Hz. This is the first time I’ve heard Focal speakers, and I must say that I’m impressed. Of all the speakers I used with the Starke Sound A2.640 power amplifier, these sounded the best.

The B&W 704 speakers are a two-and-a-half-way design with the yellow Kevlar© mid-bass cone handling both low and midrange frequencies. The -3dB point in the bass is about 40Hz. Although the Starke Sound A2.640 made these speakers sound better than I’ve heard them when using other amplifiers, the midrange clarity of the B&Ws still wasn’t quite what I was hoping for.

The B&W speakers, for some strange reason, were the least responsive to the Starke Sound amplifier’s charms. That said, the B&Ws sounded better with the Starke than they have with any other amplifier.

The two-way Klipsch is a bookshelf speaker with a horn-loaded tweeter. Mine were on about 30-inch stands. The -3dB point in the bass is around 40Hz. Despite being less expensive than the previous two speakers, the little Klipsches were the second-best sounding of the bunch, after the Focal Aria models. The Starke Sound A2.640 and the Klipsch speakers just happened to be a synergistic match.

In Haydn: Symphony in A major, Paris, Movement 1, Vivace, by Herbert von Karajan and the Boston Symphony Orchestra, the A2.640 power amplifier, even with the diminutive and somewhat forward little Klipsch bookshelf speakers managed to bring out a credible rendition of the orchestra. It certainly wasn’t front row center in Boston’s symphony hall, but it was better than I’ve heard from these speakers with any other amplifier (and by a large margin).

You won’t need $20,000 speakers to hear the superiority of the Starke Sound A2.640 power amplifier. The differences are clear even with budget gear. Do better speakers do a better job of highlighting the Starke’s virtues? Yes, they definitely do. But you won’t be disappointed even if your dream speakers aren’t the ones you actually have.

The Haydn came to life in my living room despite the modest transducers.

These tiny speakers were auditioned on the same stands as the Klipsch. The -3dB point in the bass is around 60Hz and a subwoofer brought up the bottom for these tiny tykes. Surprisingly, on some material, they imaged better than all the other speakers. But in other aspects, the HKs didn’t do as well. In fact most of the time, they sounded smooth but not as dynamic as the other speakers.

I compared in-room frequency response with other amplifiers on hand to that of the A2.640, and (as expected) found no differences. The differences that I hear from this amplifier are not frequency response related. Instead, detail, transparency, and bass control are audibly better with the A2.640, but these are measured with instruments that I do not have access to. I think that the A2.640’s excellent imaging is an artifact of an extremely low inter-channel crosstalk figure; again, this is speculation on my part. A bench test was planned for this amplifier, but due to scheduling considerations, became infeasible.

The STARKE SOUND A2.640 is the most articulate, dimensional, and powerful amplifier that I’ve heard and justifies its price with these virtues.

The Starke Sound A2.640 is the best amplifier that I’ve heard, period. Other amplifiers do come close, and for less money, but only in some respects. The Starke edges out its competition with outstanding performance in every sonic area.

Its articulate detail seems to bring out the best in most of the speakers that I used with it. The amplifier delivers stunning bass control without any loss of harmonics. Even at low output levels, the A2.640 exhibits control, definition, and dimensionality that are very rare. Those who read my reviews regularly know that I’m normally a fan of budget equipment, but in some cases, one really does get audible improvements when spending more money. The Starke Sound A2.640 power amplifier is an example.