⌈ Slovenia, officially the Republic of Slovenia (Slovenija [slɔˈʋèːnija], Republika Slovenija) – is a country located in Central and Southeastern Europe at Adriatic See (…). The capital and largest city is Ljubljana. Slovenia is the wealthiest and most developed, especially in economic terms, state of former Yugoslavia and at the same time one of the most prosperous and developed countries of Central and Eastern Europe. (source: Wikipedia) ⌋

RCHUS AUDIO is a brand owned by archus.si, a Slovenian audio distributor, which offers products of brands such as: Music hall, DLS, ASSUS, Phonar and several video brands. EGON ZONTA is the owner and a man who also wanted to offer his own audio devices. It just so happens that his friend is Saša Burian, owner of Alto Audio. Both gentlemen are Slovene and we got the PRIMUS, the basic amplifier in the Archus Audio offer, from that country. By the way, both gentlemen will participate this year in the Audio Video Show 2019 in Warsaw, where they will present most of their products.

Primus is a small, slim tube amplifier. There is something soft and nice in its artistic design - my wife immediately qualified it for "I could live with it" type of audio devices. As for tube amplifiers standards, it is really small. It measures just 370 by 325 mm and is 129 mm high. In fact, it is even smaller, but its outline is enlarged by, made of MDF, upper panel, hiding a solid, metal chassis underneath. And the chassis itself is even smaller. The device weighs 7 kg.

Tubes | The tested amplifier is a tube device with a semiconductor power supply. There are only four tubes - despite the fact that this amplifier works in push-pull mode, i.e. with two power tubes in the output. The reduction of tubes number was possible because designer decided to use interesting tube model – the PCL86 (14GW8), that in fact features two tubes in one glass - a power pentode and a low power triode. Therefore, there are two pentodes and two triodes per each channel; one of the triodes works for the preamplifier stage, while the other reverses the phase. This circuit results in an output of 8 W.

There are three chrome knobs with blue LEDs indicating their position on the front panel of the amplifier – an input selector, volume control and power switch. The MDF board can be varnished or veneered with natural veneer. The inscriptions are applied in a professional manner and look nice. The manufacturer equips the amplifier with NOS type tubes,. The reviewed unit featured tubes from the Yugoslav company EI. They are protected by an acrylic cover mounted on magnets - a nice and functional solution.

To be Modular | Perhaps equally interesting is the fact that Primus is a modular amplifier. The basic version features only line inputs (you can specify how much you need - 1 to 5) and costs EUR 2.400. However, we can equip it with a MM/MC phono preamplifier, paying EUR 330 extra. There is also an offer for people using digital sources - a D/A converter module with optical and coaxial inputs (supporting signals up to 24/192), that will cost you 164 Euros. And you can also add a Bluetooth module with the apt-X codec support for another 125 Euros. I haven't seen such another tube amplifier with that many additional functions.

Design | In the user manual, the manufacturer extensively discusses the solutions he used, so you can appreciate the effort put into the creation of this device. It is known, therefore, that the power supply works with a toroidal transformer with a power of 80 W and electrolytic capacitors with low ESR. ESR, or Equivalent Series Resistance, depends on temperature, frequency, and changes over time. The smaller this parameter, the more stable the capacitor. The power supply features a delay system to extend the life of the tubes. It is estimated for 5000-6000 hours of usage, so one set should last years before user can notice any change in the performance (and most likely they won't even notice anything). These are inexpensive tubes, there are plenty of them on the market, so using this amplifier will not be expensive. Triodes work in class A, pentodes in class AB.

The amplifier features separate transformer outputs for 4 or 8 Ω loudspeakers. The output transformers are unusual - although we know them from the Polish Fezz Audio devices - because they are toroidal transformers. They were designed by Menno van der Veen. He is a Dutch designer, known in the tubes world, also for his activities promoting tube techniques among young adepts of this art. All capacitors in the signal track are polypropylene ones - these are Wima MKP4 and MKP10s. The manufacturer talks about wide frequency response - from 15 Hz to 45 kHz, with a decrease of 0.5 dB at 20 Hz and 40 kHz. The amplifier operates without global feedback.

Good job!

| HOW WE LISTENED TO IT

Since at the same time as Primus, I tested several other devices, including the SME Model 12 turntable, I didn't have space on my rack. So I had to place the amplifier on an improvised stand - on the Sonus faber speaker stand I placed the Acoustic Revive RST-38H anti-vibration platform, and the amplifier on top of it. I placed the stand with the amp in front of the rack with other devices.

I used three signal sources: Ayon Audio CD-35 HF Edition (№ 1/50) SACD Player, Mytek Brooklyn Bridge streamer and SME Model 12 turntable with MySonic Lab Eminent EX cartridge. The amplifier drove my Harbeth M40.1 speakers it was connected to using Western Electric NOS speaker cables.

The thing that surprised me right from the start was the scale of sound presented by the Primus amplifier. It's a firm, dense sound with proper momentum - that's what we expect from a tube device. But not really from an amplifier with such tiny tubes, not from an amplifier with only 8 W output! But it does deliver richness and density, which is usually associated with powerful amplifiers featuring KT88 tubes. Come Together from the new version of the Abbey Road album by The Beatles sounded so brilliant! Same as the delicate Because and the hypnotic I Want you (She’s So Heavy).

Along with the density and richness, I also got a wide panorama. It's an amplifier that draws a vast sound stage and shows quite a lot of its depth. Simply put - there is momentum. All this is well controlled. No smudging, no bass drag, no smearing. I heard the same thing when listening to the Sunshine Of Your Love by Cream from the Disraeli Gears album. The vocals of Eric Clapton and Jack Bruce were placed exactly in the middle and had good proportions with the instruments. Clapton's guitar bit into the room on the left, and Ginger Baker's drums came from behind the right speaker. It was a coherent, nice performance.

However, you don't need to play strong music to appreciate what the amplifier can do. I would even say that it is only with music, in which silence also matters, in which the dynamic shifts are high, we can hear something more. Namely, that it is an amplifier that casts a nice "black" background behind the instruments. This is not the level of some expensive 300B amplifiers, but it is really very good. There is something to such small tubes, because I had similar impressions when listening to Leben CS-300F (EL84) and Interference Research Model 6S (6C19П).

The Archus Audio amplifier played every music with class - both the Beatles as well as Dave Holland from his latest album Good Hope. This is a recording offering spatial, calm sound, which is well shown in Tidal, thanks to MQA Studio 24/96 encoding. The leader's double bass was great - low, strong and dense. It really rarely happens that a tube amplifier, regardless of the price, plays this instrument in an equally full and so well controlled way.

It is obvious that at the very bottom the sound is rounded, that the upper treble is rather warm and "golden". But this is a low power tube amplifier so it's what you have to expect. But it is done in a sensible, nice way. Because it is a highly enjoyable, pleasant presentation. This is the thing that I found repeating most often in my notes. The device is not a typical hi-fi product, because we do not pay attention to details, but rather to the presentation as a whole, we do not delve into technical differences between CD releases, but they rather share a common denominator, they are very pleasant.

However, you should know that Primus differs from both referenced amplifiers, i.e. the aforementioned Leben and Interference Research. The tightness of the sound brings it closer to the Polish amplifier. This is a similar approach to presenting recordings as energetic "pills" that attract attention. Its resolution, however, is not so good and more like what I know from Leben. So it's really good, although not above average. And finally the momentum - in this respect it is better the other two amplifiers. And it is better equipped than them.

DAC | To be honest, I didn't expect much from the D/A converter built into the amplifier. I assumed it would be OK, I know Saša products. As it turned out, this is a mature, good product, not just a “marketing” addition to attract customers, but an equivalent part of the device. It offers an open, resolving performance, which is complemented by the amplifier's density. So, both The Modern Jazz Quartet's The Sheriff (it's the one whose cover was designed by Stanisław Zagórski) and Michael Jackson Xscape were presented in a very good way.

RIAA | The phono preamplifier is also a nice addition. However, while the DAC is an equivalent component of this amplifier, the phono preamplifier is just that - an addition. Its sound is smooth, even, pleasant. The foreground is slightly withdrawn and the sound is relaxed. With all this, however, it is not particularly dynamic and resolving. It's just that if we want to have a small, versatile device, we won't complain.

| SUMMARY

The amplifier from Slovenia showed some 'balls'. It deliver a powerful, rich performance. Even such difficult loudspeakers as the Harbeth M40.1 fell under its spell. It is obvious that as some point we will overdrive it, but by then it will be really loud and the distortion will not be tiring. This is a dynamic, colorful device that delivers low and powerful bass with good control. It sounds very natural.

The most important thing is the midrange, including its lower part. Additional modules also perform very well, in particular the DAC, which is a full-fledged element of the amplifier. All you need is a good transport (CD, BD or files) and you will have a complete system in a small chassis. A very good device indeed.

Tubes | Primus is a low power tube amplifier with a modular design. Its creators wanted it to fit into any room without any problems. That is why it is so small and so good looking. In order to fit a tube amplifier into a small package, several specific solutions were used. First of all - tubes. These are PCL86 triode / pentode double tubes, originally featured in TV sets (its audio equivalent is ECL86). Due to this choice there are only four tubes instead of seven. They are protected by a nice plexiglass plate, mounted with magnets.

Chassis | Dimensions have also been reduced by selecting toroidal output transformers instead of the classic EI ones. This choice allowed the housings transformers are placed in to be quite small in size and make them inconspicuous. And the whole chassis is quite sleek. The metal chassis is made of stainless steel, but on top there is an element made of MDF, cut on CNC machines. It is both a decorative element and part of a mechanical system that dampens vibrations. The transformer “cans” look chromed. For the test I received a demo device, the first amplifier that was built, so I don't know what the standard device offered to customers will exactly look like. In the unit I received, the “cans” were not bolted to the chassis, only fixed using a double-sided tape. I think that should be changed.

There are three knobs with LEDs that show their position on the front panel. However, these LEDs only roughly indicate the position of a given knob as there is no scale of any sort describing given position. The sockets on the back are placed quite close to each other, so we won't be able to use large diameter RCA plugs. The loudspeaker sockets are also close together, so the best solution will be to use cables with banana plugs.

Inside | Virtually the whole amplifier circuit can be found on a single printed circuit board. Separate are additional modules, the phono preamplifier, DAC and a Bluetooth receiver. The input selector features relays, and the signal runs via long interconnects to the front, to a small Alps potentiometer. On the PCB I found several high quality passive elements, for example Vishay electrolytic capacitors, as well as an advanced power supply including four independent power supplies with capacitor banks and regulating circuits.

The phono preamplifier is based on the Analog Devices AD797 integrated circuits and Wima polypropylene capacitors. The AD797 chip is an ultra-low noise and low distortion one, designed to work in audio preamplifiers. To the PCB with the phono preamplifier, a smaller board with the "Wondom" inscription is screwed from top side. This is a class D amplifier with a Bluetooth receiver.

There is no remote control. ■

Technical specifications (according to the manufacturer)

Output: 2 x 8 Ω
Output impedance: 2 Ω
Input impedance: 220 kΩ
Input sensitivity: 500 mV
Dynamics: 95 dB
Frequency range:
15-45 000 Hz (-3 dB) | 20-40 000 Hz (-0.5 dB)
Dimensions (W x D x H): 370 x 325 x 129 mm
Weight: 7 kg