The Legacy Audio Powerbloc2 stereo amplifier is a dual-mono Class D power amplifier, quite arguably, the preferred design in a high definition power amplifier. With a dual-mono design, both of the amplifier channels are completely independent of each other including having independent power supplies. This eliminates any possibility of cross-talk between channels and even greater channel sensitivity tolerances for the most ideal stereo perception. If there is also any problem or failure in one of the channels, the other remains unaffected.
Owner and designer Bill Dudleston founded his company Legacy Audio in 1983 and is well recognized as a premier loudspeaker designer for many years. At this year’s AXPONA, he demonstrated four of his Legacy Audio systems; mixing and matching his speakers and latest amplifiers for each system.
As for the Legacy amplifiers he has designed, a few years ago, if anyone had mentioned Class D in the same breath as “audiophile amplifier,” you’d rightfully be laughed out of town. From the way Class D amplifiers sounded to their inability to handle low impedance loads, they weren’t close to approaching major league status.
Today, this is a completely different ballgame. I dare say that here at Sound Advocate, I have reviewed and recommended many great class D amplifiers, including models by Wyred4Sound and PS audio, not to mention one of the finest class D integrated designs by Peachtree Audio, using ICE, Hypex, and other Class D power plants. Most, if not all of these, are some, by all means, exquisitely designed and outstanding products in their own right!
Here, we feel that Class D designs have finally reached their pinnacle of performance success and this surely cannot be denied. Some of the venerable, high-end brands are seemingly in agreement. They too have started to roll out Class D technology in their amplifiers, the latest of which is Legacy Audio with their Powerblock2 Dual Mono Amplifier which is under review here.
While Legacy Audio is perhaps best known as a high-end speaker manufacturer, amplification has been an integral part of the company’s DNA since they have been building studio-grade powered speakers for years; the first active loudspeaker being the Helix, which utilized eight channels of digital processing.
However, they now offer active speakers and multi-channel amps, but also their Wavelet DAC , Preamp/Crossover and Wavelaunch Processor provide amazing digital wizardry for their higher-end speakers, and home theater applications, and in the Pro Audio world. The improvement of a stereo amp seems like it would be comparatively easy, largely constrained by the development of Class D modules by outside suppliers, ICE– on this occasion.
Numerous refinements to class D amplifiers in recent years have resulted in improvements that not only match the neutrality of the finest high-end designs but virtually exceed these typical performance parameters in several ways:
- High damping factor
- Low output impedance
- Wide bandwidth
- Huge dynamic range
- Cool running and lightweight
- Quality construction
- Powerful with a wide dynamic range
The Powerbloc2 achieves a supremely high output on its own and is exceptionally quiet. The compact unit is extremely stable even when driven hard, and this ultra-efficient amp features short circuit protection, thermal sensing, and 12VDC triggering. The Inputs are premium hand-soldered XLR balanced and gold-plated RCA inputs, as found only on the best top-notch audio gear.
The heart of the Powerblock2 utilizes two single-channel 700ASC modules (ICEpower now calls them the 700AS1) while the Legacy Powerbloc4, a four-channel model, utilizes dual 700ASC2’s. (700AS2). The 700ASC module integrates all the essential features, such as a comprehensive protection scheme against over-current or over-temperature.
Rated at a humongous 325 watts per channel into 8 ohms, its dual-mono design offers a separate dedicated power supply for each channel, giving it exceptional stereo reproduction and it has more than enough headroom to drive the most demanding speakers as we shall see further on.
The Powerblock2 setup was quite straightforward for this evaluation. The amplifier was connected to the Pass Labs XP-12-line stage preamp for digital playback and the Border Patrol SE-1 Dac and Audio Note CD3.1×2 digital sources. An Audio Technica LP-7 turntable and the ZYX Bloom 3 (review coming) moving coil cartridge with a Cambridge Audio step-up amp performed vinyl playback duties. Loudspeakers employed were the Living Voice R25A’s, Harbeth Compact 7 EXD (review coming), and The Spendor BC1. Interconnects were the Audience Studio One’s and their Studio 1 speaker cables. Backing them up were my standard Inakustik LS-400 speaker cables.
The amplifier immediately displayed a forceful and dynamic sound quality that permeated throughout the recorded sources and the listening room. Stereo separation was immaculate and all voices and instruments on the recordings tried were perfectly placed and clean sounding; what one might call “quite immaculate” throughout the evaluation sessions.
Impressive in its huge power reserves, transients were never restrained or muffled and the soundstage was wide and dispersive in integrity and fluidity of sound fulfillment. This amplifier handled all the test loudspeakers with ease and exported a robust musicality to them with tons of power to spare.
However, when re-inserting the Pass Labs Xa 30.8 power amplifier, things took a change in reproductive quality that was a little hard not to identify. Being quite familiar with this amplifier, the initial response was implicitly bringing more air and richness to the sound, particularly the midrange and its overall nuance and detail. It also exposed that slight bit of “leanness” in the midrange of the Power bloc that was heretofore not completely noticed until the Pass Labs did some heavy lifting for a short while.
On the other hand, the Powerbloc2 compared quite decently with the Pass within the full frequency spectrum except for that slightly lanky midrange response. The bass definition was definitely on par with the later amp offering huge slam and bold transients. As most of the music is in the midrange, however, this part of the Powerbloc 2’s response was a small departure from neutrality and can by no means be overlooked within its performance parameters.
Nevertheless, to say that this amplifier as a whole is surely a solid, well-built, and very powerful unit is quite an understatement. Its overall musicality is quite neutral throughout most if not all of the full audible gamut, notwithstanding that slightly svelte midrange response.
Alternatively, the Powerbloc2 is quite revealing of interconnects and speaker cables and a few should be tried to get the most balanced sound from this amplifier. You may want to move up to some higher quality interconnects, per se as this brought out more of an accurate midrange response that otherwise can be missed on the Power Bloc 2. Try the new Audience Studio One loom or the latest, Audio Note Lexus Speaker Cables (review next week) as while the latter may be a bit less expensive than the former, they can make this or any amplifier/speaker combination sing like a bluebird!
The Powerbloc2 pricing is simply fantastic as a Class D power amplifier— and at the end of the day, this unit does just about everything that it was set out to do. It is particularly worthy of loudspeakers that need a lot of reserve power and maybe a hard, low impedance load to drive. Although at times, it may need a bit more flesh in its mid-section, it is an expansive, full-powered amplifier that is of great value and worthy of the most dedicated high-end audiophile systems.
Currently, it would be hard to find too many amplifiers that match it in its fine construction and overall sound attributes. If you are in the market for a two-channel stereo power amplifier– give the Legacy Powerbloc2 a good listen within your preferred audio system. The Powerbloc2 may not disappoint!
Review system for this product: Loudspeakers: Living Voice R25A loudspeakers, Spendor BC1, Harbeth Compact 7 ESR/XD ~ Digital: Border Patrol DAC SE-I ~ Innuos Zenith Mk.3 server/streamer ~ Wyred4Sound 10th Anniversary DAC ~ Audio Note (UK) CD3.1x/2 Analog: Audio Technica LP-7/ZYX Bloom 3 Amplification: ~ Pass Lab XP- 12 preamp ~ Pass Labs XA30.8 power amp ~ Cambridge Duo MC/MM ~ PS. Audio M1200 monoblocks / Cables/ Conditioners: Inakustik AC-3500p power station & LS-4004 speaker cables, AC-2404 reference Air Power Cord ~ Audience Studio 1 interconnects, speaker cables, Wireworld Electra 7 digital SPDIF/ Audio Art 1 e” AC Power
Suggested retail price: $2199.00
3023 E Sangamon Ave
Springfield, IL 62702
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