GMG Harmonic Hammer Exclusive

MJ08.05.2021

Power conditioners

The Exclusive version of Harmonic Hammer represents a thorough redesign of its predecessor, the model 3000P. Extra filtration stages have been added so now the sockets are filtered by a 10-stage noise removal cascade and the filtered spectrum broadened. The PowerCon inlet of the 3000P has been replaced by a 20A Furutech IEC and Furutech sockets have been used on the rear panel as well. Finally, the Exclusive version has a thicker and milled fascia that makes it look like a real flagship.

100% reference

Function and form

93%

Ease of use

96%

Sound

99%

Appearance

This Harmonic Hammer is a very heavy and a very sharp-edged piece of equipment. Dragging it upstairs was not an easy job and it made me recollect the same activity that I had carried out with two Stromtank conditioners a few months ago. Whereas the Stromtanks´ weight was result of heavy battery packs inside, the weight of the GMG owes to generously dimensioned isolation transformer, with the capacity of 3000VA.

Over the last two decades there was quite a few really good sounding audio products produced in Czech Republic, however, they often lacked flair and a visual appeal that are typical for in-a-garage production. The GMG Harmonic Hammer Exclusive is one of the rare exceptions: it is an exemplary designed and manufactured device with a lot of care to finish and technical detail.

There are two groups of sockets on the back panel of the Harmonic Hammer Exclusive, grouped by three. One group is 9A high-current for amplifiers and similar demanding components, the other group is rated 2A for source components and preamplfiers. Each group has its own low-impedance circuit breaker. On top of that, the back panel hosts the main power switch and a grounding post. The latter is of high quality, but because GMG chose to use a speaker terminal nut, it is isolated from 3 sides. If you need to ground a chassis of just one component it is fine. If you need that the grounding post accommodates more lugs (like me), then you have a problem. There is a workaround – connect all the grounding wires into one which is then terminated with a joint lug, but I would rather see more universal terminal, or terminals, on the GMG.

One control element is hidden from eyes – there is a miniature toggle switch from below the front panel that controls the brightness of the centrally placed voltmeter. The light is neutral white, dimmable in three levels, and pleasant for eyes. Apart from indicating power grid voltage, the voltmeter has dual function: in case the phase is reversed on the input of the GMG, it changes its colour to orange. And in case the voltage exceeds 255 V, the voltmeter displays red alert and shuts the outlets down. I like this type of protection; it makes me feel well cared for.

Bass management

Weight

Slam

Articulation

Recently we have seen big departure from isolation transformers in high-end audio power filtering. It has its reasons as the devices, despite providing enough wattage, were usually sluggish and were not capable of transient current delivery. On top of that, transformers tend to be noisy themselves. Therefore, it came as a surprise that GMG decided to revive the now obsolete principle. And they busted the myth. Not only has the Harmonic Hammer Exclusive watts enough (2100W of continuous output on HC sockets and 450W on LC sockets), but it does not restrain dynamics and is dead silent.

Tschaikovsky´s Symphony no.9 Pathetique with Berliner Philharmoniker conducted by Kirill Petrenko was in heavy rotation during my life with the GMG. The SACD disc is packed and presented like a piece of jewelry and the same can be said about its sound that is a demonstration of what the digital, in right hands, is capable of. It is brilliant, explosive, colorful, dynamic, detailed, and smooth at the same time. So, how did it sound ‘through’ the Harmonic Hammer Exclusive?

The filter proved that it was a non-limiting device that did not make any harm to the sound and music and can be compared with the very best power conditioners. For me, an unconditioned system was not the benchmark as I am using Shunyata Research and Stromtank products, as well as I lived with Synergistic Research’s and Ansuz’s top end power distributors. If your system is plugged directly into the wall, then the Harmonic Hammer Exclusive will be capable of lifting it up to much higher level. Dtto for the systems that use simple extension socket blocks like Nordost’s QB. So I spent my 3 weeks with the GMG filter endlessly comparing it my Shunyata Denali and Stromtank S-1000.

Clarity & delicacy

Detail

Air

Transparency

Let me take the Denali first. I was expecting quite a difference due to the completely design different principle of Shunyata and GMG and was surprised that they were pretty close to each other. Both the devices could push down the noise floor to negligible levels, so new details in the music come up. The Denali outperformed the Harmonic Hammer Exclusive in how these details were locked within the soundstage; the soundstage of the Denali was more accurate and more three-dimensional. For instance, an oboe solo had better vertical perspective against strings, as well as the distance from the strings to the oboe was clearly heard. Cellos were a section of individual instruments through the Denali, they remained a section through the GMG.

The GMG Harmonic Hammer Exclusive won over the Denali with richer sound that had better substance, perhaps it was also a smidgen more colorful. It took me quite a few recordings (and days) that I arrived at the following: the Harmonic Hammer Exclusive sounded more complex bottom up; it worked with a wider palette of blacks and it made the music thicker and more relaxed presentation. When switching to the Denali I missed this density of sound. On the contrary, the Denali was better in all the shades of silver; complicated percussive textures, harp strings and flutes were more natural and more alive through the Denali. Still, the differences were not profound, rather nuanced.

Tonal accuracy

Timbre

Dynamics

Temporal resolution

The Stromtank S-1000 was the challenger number two. The GMG Harmonic Hammer was a real powerhouse that energized connected components in quite an exciting way – it is as if there was more juice available than could be found in the power grid and the music had great slam. That is why well recorded pop music, electronic music like Yello and Front 242, soundtracks, and rock sounded so good through the Harmonic Hammer Exclusive. However, where the music asked for more finesse, the Stromtank ruled. It had a higher level of how the sound was organized and it sounded more composed, relaxed, and natural. One could hear it especially on acoustic instruments like pianos, acoustic guitars and violins, that were truer to the source with the battery based Stromtank. It was with the Stromtank when I started to realize a subtle signature of the Harmonic Hammer Exclusive, which always seated me a bit farther from the stage than competitors, its sound was embracing and grander. This was not a bad thing as I could stop listening for details and could enjoy the music as a whole.

Spatial resolution

Holography

Soundstage width

Soundstage depth

Even with the power amplifier the Harmonic Hammer Exclusive could provide enough juice and was one of the few that I could use for entire system. I am far from saying that you can connect any power amp to it, however, unless you have really hungry beasts, it will work with most. When I listened to Rachmaninov’s Sympohonic Dances (The Philadelphia Orchestra, Yannick Nézet-Séguin, DG) I did not miss dynamic swing, quite contrary. Compared to the Shunyata the GMG was hitting harder and provided me with the orchestral climaxes line anything else. Still, when I listened carefully, I could hear that the Shunyata had better control over contours of the timpani and - as described earlier - was better in imaging. Despite this nit-picking the GMG was big and smooth and a kind of addictive. I wished I could have a toggle switch between both conditioners to choose depending on my mood.

The power filtration must be seen in the context of the system, and therefore needs your personal experience. Also incoming and outcoming power cables will have big impact. I tried seven different cables from the wall to the GMG and got seven different sounds. Let me conclude like this: in the case of the GMG Harmonic Hammer Exclusive any discussion about whether to filter or not is useless. The Hammer is an incredible achievement with no ‘buts’ and can confidently challenge any reputable power filtering solution on the market. I am proud that it is designed and made in Czech Republic.

Price as reviewed:410 000,- Kč

Recommended resellers

GMG Power, Nedakonice, tel. +420 739 626 436

Manufacturer's website: http://www.gmgpower.cz/

Associated components

Sources: Accuphase DP-720
Amplifiers: TAD M-2500, Aavik I-280
Interconnects and speaker cables: AudioQuest Dragon Bass | Zero, Krautwire Numeric Digital, Krautwire MAX-S, Ansuz Signalz C2, Accuphase RCA
Loudspeakers: TAD Evolution One E1, Sonus Faber Gravis I
Power conditioning: Shunyata Research Denali, Stromtank S-1000, GMG Power Harmonic Hammer Exclusive, Synergistic Research Atmosphere Level 2, Ansuz Mainz C2, Ansuz Mainz D-TC, Authentic Audio Image Maestoso, Block Audio Snakeblock, Roth Audio prototypy, Nordost Qv2

Gallery

Sound

90%

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