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Power supply DC


Producent: HEM
Price (when reviewed): 995 EUR (with VAT)

Contact: Al. Jerozolimskie 475
05-800 Pruszków | POLSKA



Provided for test by: HEM


Images: Ferrum | Wojciech Pacuła

No 200

January 1, 2021


FERRUM is the newest Polish audio brand that has just been established. But behind it there is HEM, one of the most experienced audio companies, that has been designing and manufacturing devices for the MYTEK brand for 20 years. Ferrum's first product is the HYPSOS power supply, one of the most advanced DC power supplies on the market. We are the first in the world to test it.

HEN I SAW THE FIRST HYPSOS DESIGNS, I was very impressed. These were the so-called "Renders", i.e. computer 3D drawings, but they already gave me an idea of what the power supply was to become. However, nothing prepares you for how this device looks in real life and what it can do. And it looks amazing, both thanks to the fragment of the front panel made of Corten and the color display, and it is also the most functional and user-friendly product of its type I know.

Let me introduce its "guiding spirit" and patron, MARCIN HAMERLA. Let me also remind you that we have just published the first extensive interview with Marcin and PAWEŁ GORGON, the head of his designers, in which they talked about their cooperation with Mytek - see HERE http (HF | № 182 • June 2019).

| A few simple words…

Owner, director

⸤ MAKS MATUSZAK designing the Hypsos PS; there is the Mytek Brooklyn Bridge on the desk in front of him, and he uses Audeze headphones.

The idea to found a new brand was born about two years ago. It was related to the fact that, although the 20-years long cooperation with MYTEK was very successful, it made us feel that we would like to do many things differently than within it. How? - bolder and while having a full control over projects. A stable brand with traditions like Mytek requires a different approach to products than in the case of a new brand, where you can let your engineering imagination run wild and do things boldly, without looking at the past. It is important and must be kept in mind, but it also imposes some limitations that we have decided to discard.

An important aspect of our decision was my success in „bringing up” a very good, young designer team with a splash of collective genius, which I noticed while working on the last products we developed for Mytek. It sounds lofty and not modest at all, one could say - quite "not-Pole-like", but at the same time it is consistent with the facts.

Such a team needs challenges, new, ambitious goals. One such goal was to design a universal audio power supply that we called HYPSOS. Why the power supply? The reason is simple. Power is the backbone of any electronic system. In audio, it is the very foundation which the final result is built upon. Without an effective and well-thought-out power supply, there is no way that the D/A converter or preamplifier will sound as the designer intended. Therefore - Hypsos..

Hypsos is a result of a collective work. It is not the work of an acquainted inventor. Its project is the result of work of a group of involved, dedicated people, whose goal is to perfect the engineering craft and build advanced audio devices that move the quality of sound reproduction a step further up. Always a step further up - that's how progress is achieved after all.

Having said that, I would like to name the three people that are now representing the team. It is MAKS MATUSZAK, who designed the analog part of Hypsos, PAWEŁ GORGOŃ, head of the R&D office at HEM, whose talents allowed for efficient software development, and PRZEMYSŁAW GÓRNY, who cares about putting everything together.

HYPSOS IS A DC POWER SUPPLY and a hybrid linear-switching design; Company materials refer to it as "Hybrid Power System". In the company materials it reads that such a design ensures "low ripple and noise, as well as a fast transient response and high quality sound". The second advantage of this type of design is that the power supply is relatively small.

When we look at it, we will see that it is in a sense a twin product with the Mytek Brooklyn Bridge player. The Hypsos has similar dimensions (it is slightly higher), as well as the same distribution of elements on the front panel. In its center there is a display, or actually two of them, forming a whole, identical to those used by the company in Mytek. On the right side there is a knob which, when pressed, is also used to confirm the selected menu item.

An important property of the Hypsos is that it is up to the user to select the output voltage. The voltage ranges range from 5 to 30 V, so the power supply will work with almost all devices available on the market. It is characterized not only by a wide range of output voltage, but also by a very high current output. It guarantees 6 A for voltages below 10 V and output up to 60 W for higher voltages - so it can power any D/A converters and preamplifiers.


THE ELECTRONIC CIRCUIT OF THE HYPSOS POWER SUPPLY is entirely proprietary. As Marcin Hamerla told me in the telephone conversation, there are no "from the shelf" components in it, and the whole thing was designed by HEM. It is a hybrid system with a classic linear power supply with a transformer and capacitors to reduce ripple noise. They are followed by a converter, i.e. a switching mode power supply, which reduces the noise to even lower levels.

Instead of the industry's standard LDO (Low Drop Output) voltage stabilizers, a proprietary design was used - elements with trigger points digitally controlled by a microprocessor. Thanks to this solution, the output instead of 1A is 6 A, and even up to 9A, because then the limiter kicks in. The head of HEM said that the company declares an output of 60 W, but in reality it is even 80 W, with momentary peaks up to 200 W! Power supplies offering such a high output usually look like medium-sized integrated amplifiers.

TOGETHER WITH THE TESTED DEVICE one receives a short DC cable, terminated with 5 × 2.5 or 5 × 2.1 mm plugs. There aren't many different cables in the box, because we don't usually use them anyway, and this - as it reads in the press materials - has a negative impact on the environment. The company offers power cables with any DC plugs, but you will have to pay extra for it. Interesting fact - we can control the power supply, that is, navigate through the menu using the Apple remote control.

I mentioned two elements that constitute this product - the Corten and the display. KORTEN (corten), also known as rusting steel or Corten steel, is a steel of increased endurance, which when subjected to moisture is naturally covered with a characteristic coating resembling rust (from:, accessed on December 9, 2020).

Its appearance in the Ferrum device, as well as the name itself, are not accidental. As Marcin Hamerla, the founding boss of the HEM company, i.e. the manufacturer the Ferrum brand belongs to, told me, he wanted to refer to the place where the company has its headquarters, and where numerous bloomers with lumps of molten iron in them where found.

The DISPLAY I mentioned is indispensable in this case - the Hypsos is "only" a linear DC power supply, but its functionality resembles that of amplifiers. It features a microprocessor control, programmed by HEM team and thanks to it it was possible to “arm” the power supply with such extensive functionality. The display shows the selected output voltage, supply voltage, current consumption, power consumption, as well as the voltage polarity in the plug on the side of the powered device.

It will also display a list of devices that are powered, so we do not even need to know the voltage required for them, just select the product. If it is not on the list - we do it manually. However, this is only an introduction to the settings. The manufacturer enables us to do something more. The first of the possibilities of influencing the sound is related to the precise regulation of the supply voltage, indicated by the "bar" on the display. This function was named SWEET SPOT TUNING (SST), referring to the so-called "Sweet spot", which is used to define the ideal listening position in audio.

Sweet Spot Tuning offers:

Possibility to fine tune the output voltage for the best sound. The voltage level can be safely adjusted on the fly to allow easy comparison testing.

FERRUM.AUDIO, accessed: 09.12.2020

The company "glossary" also includes an abbreviation: 4TSD (4-TERMINAL SENSING DESIGN). It is a technique that allows you to maintain the exact voltage level exactly at the point of supply, not the "planned" voltage. The power cable has a special four-wire structure in which a pair of cables provide voltage and the other pair is part of a feedback loop that maintains the intended voltage at all times, regardless of the current draw. This technique - as it reads in the company materials - eliminates the harmful effects of cable resistance, effectively improving the transient response.

And finally, there is the SSM (SPREAD SPECTRUM MODE). This is a special mode in which the converter does not work like most converters, ie at a fixed frequency, but at a variable (by 20%)range of the nominal value. Thanks to this solution, the distortions do not arise in the system only at the frequency of the converter and its multiples, but they are "spread" over the whole band, so their total level is much lower.

Thus, there are much less harmonics in the supply voltage that could penetrate the audio signal from the supply via modulation. As Marcin Hamerla says, it is due to the SST mode and the use of another linear power stage, that it was possible to eliminate the disadvantages resulting from the operation of the converters, while preserving the advantages of both supply topologies, i.e. very fast response to impulse current, small dimensions and high efficiency.

Can you see it? - Just compare the Ferrum Hypsos power supply with any one you get with your DAC or preamplifier (also routers and LAN switches), and even against any other, advanced power supply from one of the specialist companies, and you should know what I am talking about. Because there is no doubt, this is an absolutely unique product on a global scale, a pioneering top shelf product.


HOW WE TESTED IT The tested power supply was listened to with the Mytek Brooklyn Bridge file player. Mytek worked as both an integrated audio files player and as a digital-to-analog converter, with the signal sent from the Lector Digidrive TL-3 CD transport. I separately compared it to the Nordost QSource, which is connected to QPoint generators in my system. Both the player and the power supply were powered using the Acrolink 8N-PC8100 PERFORMANTE NERO EDITION cable.

Recordings used for the test | a selection

⸜ CANNONBALL ADDERLEY, Somethin’ Else, Blue Note/Esoteric ESSB-90125, SACD/CD (1958/2015) w: 6 Great Jazz, „MasterSound Works”, Blue Note/Esoteric ESSB-90122/7, 6 x SACD/CD
⸜ FRANK SINATRA, Nice’N’Easy. 60th Anniversary Edition, Capitol Records/Universal Music LLC (Japan) UICY-15883, CD (1960/2020)
⸜ NORAH JONES, Pick Me Up Off The Floor, Blue Note Records B003179801, Compact Disc (2020); ⸜ EDDIE HIGGINGS QUARTET, My Foolish Heart, Venus Records TKCV-35532, gold-CD (2005)
⸜ JAROSŁAW ŚMIETANA, Sounds & Colours, Polskie Nagrania „Muza”/ Polskie Nagrania | Warner Music Poland 9 51609 6, „Polish Jazz” vol. 73, CD (1987/2020)

⸜ ELLA FITZGERALD & LOUIS ARMSTRONG, Ella and Louis, Verve, FLAC 24/96 (1956/2000).
⸜ LARS DANIELSSON & LESZEK MOŻDŻER, Pasodoble, ACT Music, FLAC 24/88,2 (2007)
⸜ LEONARD COHEN, Popular Problems, Sony Music Labels SICP-4329, CD (2014); ⸜ METALLICA, Metallica, Electra | Warner Brothers Records, FLAC 24/96 (2006)
⸜ NAKANO MAYO PIANO TRIO, Sentimental Reasons, Briphonic BRPN-7006, Master DSD64 (2017);

DESCRIPTION OF THE SOUND of the tested device I would like to start with the description of the IMPRESSION that remained after listening to the Mytek Brooklyn Bridge with and without the Ferrum Hypsos power supply. 'An impression' is defined by PWN Polish Dictionary as "a mental state, mental reaction caused by a stimulus", "experience, especially strong one" or "conscious reaction of the sensory organ to an external stimulus". In a word - it is a mental reaction caused by an external stimulus. This time it would be about how I "responded" to this new sound.

I am starting with it, because regardless of what I "discovered" during the listening sessions, what "turned out", or what conclusions I drew from these volitional, i.e. initiated by me, actions, the most important thing was what happened outside of my will, to some extent - against me and my plans. And the impression was based on the abrupt change in the pleasure level I listened to music with with the files player connected to the tested power supply, as well as the equally significant increase in interest I listened to it with.

The thing is that the power supply transforms the sound of Mytek. It does not even 'change' or 'modify', but does something more thorough, more comprehensive and simply more important. In short - it makes this incredibly correct sounding, incredibly reliable and simply in every way good sounding file player to start sounding like a much more expensive device. Not just twice as expensive, but much more expensive one. Perhaps it is not that important that it sounds more expensive, although it is true, but - that is sounds better, much more refined.

The power supply does something with the sound of the Mytek, which makes the presentation on the one hand softer, more natural, and on the other hand more resolving. I could clearly hear it when listening to recordings in which the vocal is slightly brightened and quite heavily compressed, like Leonard Cohen's voice on the Popular Problems, or Norah Jones’ in the Pick Me Up Off The Floor (Jones has been nominated for the 2020 Grammy Award!). These are very good productions, but this particular element was prepared with car radio listening in mind.

Anyway, the Ferrum power supply makes the sound much nicer. Both vocals were moved back by half a meter, which was good for them. Recorded up close, they can "pop" out of the mix, making it seem as if the vocalist is standing in front of the band. And there would be nothing wrong with that, if his/her image was not so flattened and angular. Ferrum caused both Cohen and Jones being better integrated into the band, and at the same time their „bodies” were bigger and more three-dimensional.

The albums listened to in this way were much more interesting. Several times I noticed that after plugging in the power supply - and I tried to compare individual tracks to remember their sound - I was sitting up on the couch (I was listening sitting on the couch) and "looking for" the sound. The sound with the power supply was deeper, denser, but also better differentiated. As I said, it seems darker then, because the upper treble is no longer as “present”.

However, the treble is not actually withdrawn, because the sound of the cymbals from the Jones disc, or wind instruments, as from Cannonball Adderley’s Somethin ’Else, was stronger, there were more details and subtleties in it. So - darker - but clearer, further away - but more precise, more vivid - but also more dynamic. I recall pairs of sonic features, which should look exactly the opposite, because 'darker' should mean 'less detailed', right? - Well, it’s not, at least not in this class of devices - Mytek connected to Ferrum moves up to a completely different category.

However, the Polish power supply does not impose its own sound. I noticed that some recordings sounded less smooth and less rounded with the Ferrum than without it. This was the case with recordings from the Ella Fitzgerald & Louis Armstrong album entitled Ella and Louis, which I played from FLAC 24/96 files prepared by the Verve label, as well as with Frank Sinatra's album Nice'N'Easy. 60th Anniversary Edition, played from a CD.

The point is that their voices were recorded with a slight "excess" in treble, somewhere around the 10-12 kHz range. It manifests itself with a certain brightness, but also better clarity. Mytek itself played these albums in a very pleasant, dynamic way, with a wide panorama in the case of Sinatra and with a nice volume on the axis in the case of the monophonic album of the Fitzgerald & Armstrong duo. But it also rounded the treble that I am talking about, as if it could not recreate it so accurately. Ferrum extracted much more information from the recordings and cleaned the voices enough to make this element clearer than before.

The curiosity I mentioned at the beginning comes from the level of the presentation’s saturation with information, and thus from a more natural sound. Natural, i.e. deeper, less "square" and rough, but also with more information. It is also quite clear when we compare the spaciousness of the Mytek with and without the power supply. Without it, the converter shows the instruments in a very cool way, differentiating both their individual spatial aspects and the way these micro-worlds make up the whole performance. Hypsos is changing the rules of the game. It broadens the scene, deepens it, also around us.

⸜ TUNNING The manufacturer of the Hypsos power supply offers its users ab option to influence the sound of the devices connected to it. These include: changing the output voltage (Sweet Spot Tuning), the Spread Spectrum Mode system, and the ability to disable the 4TSD (4-Terminal Sensing Design) system. Each of these settings changes the sound, but the first of them affects the sound the most.

The adjustment of the output voltage can take place within a safe range, which the HEM company has set at 8-13.5 V for the nominal output voltage of 12 V. In fact, this range is different for each device, as specified by its manufacturer or, if not specified, it should be within ± 5% of the nominal value. The company did it this way to maintain a compromise between security and tuning ability.

As far as I can hear it, the changes work similarly to the tone control. They are not that big, but they can be important. Generally, the voltage above the nominal one thickens and lowers the sound, and below it - the other way round. For me, Hypsos worked best with Mytek at 13-13.5V, but you may like a different setting, there are no rules here.

Both the Spread Spectrum and the 4TSD, i.e. the inclusion of power cord feedback, have a much smaller effect on the sound, just underlining a bit what we selected by adjusting the voltage. But they emphasize the benefits of regulating the voltage nicely, so for me, both should be active.

| Summary

I DON'T KNOW ANY OTHER POWER SUPPLY, which would be equally versatile, equally functional and easy to use and also - for me this is an important aspect - good looking and made to last. Behind Hypsos there is real engineering, as well as proprietary solutions that you will not find anywhere else. And sound wise - now I can't imagine playing music using Mytek without Hypsos. All owners of this device should already start saving money. And not only them - the Ferrum power supply takes the sound to a much higher level and once heard it is hard to forget.

I would not buy a Ferrum without trying it out first, there are other power supplies on the market, also very good ones, such as the great OPTIMO 3 DUO by JCAT (also Polish product, review HERE), which will power two devices separately. It may turn out that it will get along better with your D/A converter, router, preamplifier or headphone amplifier. However, the Ferrum Hypsos is such an amazing product that it cannot be overlooked, regardless of the price of the product to be powered up.


ALL THE BASIC INFORMATION about the appearance and functionality of the Ferrum Hypsos power supply have been already presented above. Now let me add that the chassis of the device is made of thick steel sheets, and the front panel - with the exception of the Corten fragment - of aluminum. The company logo is laser-cut in the Corten and illuminated in white. The brightness of the logo and display can be adjusted in the menu. The device features small, rubber feet and this is the only component that could be easily improved.

On the back there is an AC power socket integrated with a fuse and a on/off switch, as well as a DC socket to which we plug the DC power cable. Both the socket and plug are of excellent quality. They were selected from the top shelf of industrial technology - they come from WEiPU (Series 12). I will add that the socket has a bayonet latch. The plug on the other side is also very good which can be a challenge, because there are only a few companies that manufacture high quality ones. Unusually for an "engineering" company, the DC cable is also a very good one - it is a Canare cable, manufactured in Japan.

Inside, the Hypsos looks as if it were a D/A converter with a linear power supply. Half of the interior is occupied by a large toroidal transformer with a resin flooded center, preceded by a two-stage EMI filter. The PCB hosts four large network ripple smoothing capacitors and many surface-mounted operating circuits that are part of voltage regulating circuits. In the front there is a large microprocessor circuit that controls the operation of the device. Input and output voltage are switched by relays.

It's a professional, minimalist design based on proprietary solutions that I've never seen before. And this wonderful Corten piece - fantastic!

Technical specifications (according to the manufacturer)

Power input: 100-240Vac/50-60Hz (EU/US Version) 90 – 110Vac/50-60Hz (JP Version)
Output Voltage Range: 5-30 [V]
Max Continuous Output Current (for V_out below 10V): 6 [A]
Max Continuous Output Current (for V_out higher than 10V): l_out= 60[W] / DCout[V]
Max Continuous Output Power (for V_out below 10V): P_out = V_out[V] * 6[A]
Max Continuous Output Power (for V_out higher than 10V): 60W
Dimensions (without knob, feet and connectors) (W x D x H , mm / inches): 217.5 x 206.5 x 50.0 / 8.6 x 8.1 x 2.0
Net weight (kg): ~ 2,8


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