The Stromtank is the brainchild of Wolfgang Meletzky, whose name has carried weight in the hi-fi world for decades. The Berlin-based electrical engineer first gained recognition through his extraordinary loudspeaker designs, which shook up the industry and laid the foundation for one of Germany’s most renowned high-end brands.
With Stromtank, Meletzky wanted to return to his roots. His mission was to develop a product that would return high-end systems back to the sound quality they used to achieve. And this is in the past tense, because in the past power grids were far less contaminated by high-frequency interference. In turn, the market has responded to these problems for many years with power conditioners, isolation transformers, and numerous accessories. But in the end, they’re just Band-Aids, and Meletzky doesn’t believe in these temporary solutions. So he decided to completely rethink the problem. Rather than simply filtering or smoothing the signal, he wanted to rebuild it entirely from scratch, free from the public power grid.
When the S4000 ProPower MK II was delivered to us, we quickly realized that it demands more than just curiosity. The gross weight of 115 kilograms alone made unloading a challenge. Without the help of a few neighbors, I don’t think I could have gotten the crate up to my raised ground-floor apartment. However, after this feat of strength, the transport packaging quickly distracted from the exertion: a massive and yet precisely-crafted wooden crate with a deliberate and careful design. Simply open the side panel, which doubles as a ramp, and the Stromtank can be extracted surprisingly easily. Despite its net weight of around 80 kilograms, it glides across the floor on built-in sliding feet.
Immediately I was caught by the enclosure’s high-quality workmanship immediately. Every edge is perfectly finished, and every surface is precisely machined and painted. The slightly beveled front surfaces make it look less bulky than its substantial dimensions of 54 centimeters in height, 48 centimeters in width and 59 centimeters in depth. Stromtank’s unmistakable appearance is partially defined by the central porthole with its needle meter—I’m told that this instrument is inspired by the classic round gauges of German sports cars. And so the porthole exudes powerful elegance, remaining distinctly technical without any pretentiousness. The needle expresses just how much power the Stromtank is currently delivering or absorbing, while ten LEDs directly below visualize the state of charge. To the left and right of this LED strip are two buttons: One controls charging and discharging, as well as switching the unit on and off; the other controls the lighting in discharge mode, which can be dimmed or completely deactivated. Mine remains permanently on, because I fell that the green illumination generates a pleasantly technical, almost mysterious aura. These two buttons are also found on the extremely compact tabletop remote control. It is as minimalist as it is functional, and resembles a small technical sculpture. Its satin-finished aluminum housing means that it sits perfectly on the table. To summarize, down to the smallest details, the impression is, as is typical with German design, flawless.
The Stromtank is manufactured in a small Berlin workshop with just six employees. Each unit is handmade, with approximately one hundred units produced annually. And the concept is as ambitious as it is logical: the Stromtank completely disconnects the connected hi-fi system from the power grid and instead supplies it with energy from an integrated, extremely powerful battery system. Inside are lithium iron phosphate cells that are monitored by a computer-controlled management system. In conjunction, this creates a completely clean, stable, interference-free power supply, which is completely free from voltage fluctuations, RF interference, or other external influences. This energy storage system not only delivers more stable power than any wall outlet could, but also provides the system with an autonomous, controlled environment.
The storage capacity is 2,700 watt-hours, supplied by a 48-volt DC battery architecture. Inside, two inverters operate in parallel, delivering an output voltage of 100 to 130 volts or 200 to 245 volts in a pure sine wave. The transfer time between grid and battery operation is less than 15 milliseconds—below the threshold of perception. Continuous output power is 950 volt-amperes at 25 degrees Celsius. Furthermore, short-term peaks of 1,500 volt-amperes for three minutes and even 3,700 volt-amperes for three seconds are available. On the rear panel are four high-quality Furutech Schuko outlets (optionally also available as pure copper or rhodium-plated duplex sockets). This power reserve means that even power-hungry Class A amplifiers can be operated for hours without ever pushing the Stromtank near its limits or risking even the slightest voltage drop.
When connecting the unit, you immediately discover how well thought-out the system is. Even technophobes can find their way in from the start with the help of the clearly structured quick-start guide. For example, if the power plug is inserted with reversed polarity, then a green LED discreetly points this out. When everything is connected correctly, you first turn the key switch on the rear panel. Then, you switch on the main power switch, at which point the display in the porthole glows blue. Thus the charging process begins. After that, activate the separate circuit breaker for the output sockets, which are further protected. This multi-stage power-up concept ensures safety and clarity and reminds you that you’re operating a precisely controlled energy system.
As the fully charged Stromtank S4000 takes control of the system, the effect is instant. You don’t need to prick up your ears in search of differences—everything becomes clear. The entire frequency range feels tighter, more controlled, and yet calmer. The soundstage opens up in width and depth, while instruments and voices gain precision and localization. To be frank, the music sounds liberated, as if an invisible layer between system and listener had been removed. What’s particularly fascinating is what you don’t hear. The space between the notes becomes a pure vacuum in which every detail stands out with crisp definition. This true silence is utterly surreal—it’s as if you were sitting in a theater and the actors were standing in front of a deep black curtain instead of a restless, colorful backdrop. The ear focuses exclusively on what matters, and all distractions are gone. I had thought the effect would be most noticeable during the day, when the public power grid is more heavily loaded by many consumers. After all, many systems sound better in the evening when the line voltage is calmer and more stable. But even late at night, when hardly any interference is present, the Stromtank demonstrates a definitive improvement.
So it’s time, then, to listen to a few familiar pieces of music. I started with Pink Floyd’s “Shine On You Crazy Diamond.” From the very first bars, the sound was completely detached from the speakers. The atmosphere naturally unfolded into the room, transparent and three-dimensional. When the saxophone came in, the illusion was perfect. It floated tangibly in the space, with body, breath and warmth—so believable that, with eyes closed, I could swear a real musician was standing before me. This kind of authenticity is rarely achieved elsewhere, and here it came effortlessly. Next, I put on Gianna Nannini’s album Perle, specifically the track “Profumo.” Her distinctive voice sounded with a closeness and intimacy that was practically tangible, the cello beside her corporeal, full and true-to-life. No harshness, no exaggeration, just music in its purest form. Especially with such quiet, emotional recordings, it resounds how strongly this “black background” shapes the sound image. Every small nuance, every breath emerges more clearly, without ever sounding analytical.
Next, I was curious to see how the Stromtank would perform with more dynamic recordings. The distinctive harmonica intro of Supertramp’s “School” stretched out wide in the room, with each instrument firmly anchored in place. When the bass arrived, it sounded not only deep and powerful, but also precise and springy—just as it should be live. Sonic order was maintained even in the loudest passages. No collapse, no congestion, with the stage remaining open, stable and easy to follow. The drums cracked with authority and without harshness, while the piano and vocals effortlessly asserted presence. The Stromtank doesn’t just provide more calm, but also significantly better dynamics.
To conclude my listening, I put on Igor Stravinsky’s Le Sacre du Printemps. Few works offer as many contrasts, such extreme dynamic shifts and such a fascinatingly complex rhythmic structure. The Stromtank gave the orchestra space to blossom with tremendous ease. The massive tutti passages virtually exploded into the room, without ever sounding aggressive. At the same time, even the quietest woodwind detail retained pure clarity. The drama of this piece—its untamed energy and orchestral force—became fully tangible in all its depth. The system never once reached its limits. Instead, it engaged a sovereign control, as if every musical gesture were illuminated against a deep black, silent background.
After hours of listening, I realized that the Stromtank S4000 ProPower is not an accessory in the conventional sense, but rather a fundamental change to the entire power supply, and thus to the very foundation for any system. Of course, the price of around €33,000 is no small matter, and one might even consider it excessive. But anyone who has experienced the S4000 understands why it exists. Even the last skeptic will realize the decisive role that clear energy plays in the high-end realm. In short, anyone who truly wants to know what their hi-fi components are capable of should at least give the Stromtank a try. Many good dealers offer loan units, and I’m confident that, in most cases, the device will end up staying with the customer.
Power filter/battery Stromtank S4000 ProPower MK II
Concept: grid-independent energy system with high-performance battery operation | Batteries: computer-controlled lithium iron phosphate battery with dual inverters in parallel operation | Storage capacity: 2,700 Wh at 48 V DC system voltage | Output voltage: 100 to 130 V AC or 200 to 245 V AC, pure sine wave | Power: 950 VA continuous, 1,500 VA (3 min), 3,700 VA (3 s) | Transfer time (grid/battery operation): < 15 ms | Connections: 4 × Schuko (Furutech NFC) or 4 × Duplex (pure copper, rhodium plated) | Special features: handcrafted in Berlin, limited annual production of approx. 100 units, powers even high-performance Class A amplifiers for hours with absolutely clean electricity, remote controllable | Dimensions (W/H/D): 48/54/59 cm | Weight: 80 kg (shipping weight 115 kg) | Warranty: 3 years | Price: around €33,000
Stromtank
Rathenower Straße 45
10559 Berlin
Phone +49 30 52688330
info@stromtank.com