A young South Korean brand discovered through its network servers, HiFi ROSE is launching its HIFI ROSE RA180 integrated amplifier, whose two main features – using class AD and enabling bi-amplification – provide real added value, as well as delivering considerable power to speakers, while creating a smooth, airy sound.
Among the most innovative manufacturers of the moment, HiFi ROSE stands out thanks to its network players, whose main distinguishing feature from the competition is their complementary nature, in particular the addition of HDMI inputs and the integration of YouTube, enabling the audio player to be linked to a video system. The brand’s engineers are now taking the same approach to amplification, with the idea of drawing on the best of all existing technologies to create a highly versatile device. And so the HIFI ROSE RA180 was born.
Class AD and bi-amplification
Starting out as a simple integrated amplifier, without a DAC, where we might have expected a full digital function from a specialist in the field such as HiFi ROSE, the RA180 develops a digital approach to amplification via class D, while using a hybrid mode to create a class AD, whose warm sound brings us much closer to the sonic atmospheres of class A than of class D. To achieve this, the main innovation is the use of gallium nitride (GaN) FETs, which have a dead time ten times lower than that of conventional FET semiconductors and therefore offer a much faster switching speed, with the result of developing the linearity of Class D to higher levels than those usually found. You therefore benefit from the linear power, speed and extremely low distortion associated with this digital class, combined with many Class A components.
The power supply is provided by Silicon FETs (SiC) implemented on a proprietary PFC circuit whose processing offers a damping factor close to 200 and an available output power of over 1,000 W.
In addition to these technologies, the RA180 also stands out for its structure, made up of four independent amplifier modules, which not only allow bi-amplification on two pairs of speakers (since there are two stages of eight terminals at the rear of the unit), but also take advantage of a BTL (Bridge Tied Load) mode, which creates a bridge to link the loads and then multiplies the supply voltage power by four. With this technology, the power of 200 W under 4 and 8 ohms for four channels is increased to 400 W for two channels. With an unrestricted frequency range, much higher than that supposed to be audible to humans, particularly in the high frequencies where it peaks at 90 kHz (compared with 20 kHz audible), the HiFi ROSE is ideal for adding a pair of super-tweeter speakers to your loudspeakers, like the Townshends covered in the previous issue (see VUmètre No. 41).
Old-modern design
Even more so in real life than in photographs, the ROSE RA180 looks like a big toy straight out of the great hi-fi years of the last half-century. It’s impossible not to mention the Nagra reference, particularly in the vumeters, but beyond this influence, the amplifier displays its own personality as well as a genuine quest for ergonomics. From right to left, multiple buttons and selectors enable standby, the choice of speakers A or B to use the high or low line of terminals, a pure direct switch, and the possibility of using a subsonic filter or an attenuator. Then a large knob, made of aluminium like the rest of the front panel, is used to vary the volume using a set of interlocking notched circles, the level of which is reflected on a graduated bar just above.
Two illuminated meters on a yellow background mark the end of the right half of the unit, which is still very busy on the left to adapt the type of sound desired. In addition to different levels of gain and frequencies on the RIAA curve when using the internal phono preamp, an active filter limits low frequencies in order to improve high frequencies and therefore produce a finer sound. Then the preamplifier section offers something rarely found on European products and almost always on Asian amplifiers: balance, treble and bass management. A final selector on the far left allows you to choose the input, which is of course connected to the rear panel: three pairs of RCA sockets, a pair of XLR sockets and a pair of RCA phono sockets.
Supported by three large, vibration-resistant aluminium feet, the RA180’s interior is topped by an attractive nameplate that adds to the retro style, and bears the name of the device as well as its main feature: the use of gallium nitride. The rear uses a Furutech mains connection and offers two grounds for connecting both the amplifier to earth and to the ground of a turntable. In addition to the five pairs of analogue inputs mentioned above, the amplifier’s most impressive feature is the four blocks of four terminals which, when BTL mode is activated, deliver an extraordinary sound by combining four mono amplifiers linked in pairs.
The set up
Weighing in at a hefty 16.7 kg, the ROSE RA180 cannot be placed on just any stand, and we recommend that you use a quality hi-fi cabinet to support it. It is easily connected to the mains, to sources – including a vinyl turntable – and to speakers. This last part is where its real specificity lies, because while conventional connection of the left and right speakers is perfectly possible, it is ultimately rendered obsolete by the BTL bridged mode, which consists of connecting both sides of each speaker to the right terminal block of each of the eight pairs. So, the already comfortable power of 2 x 200 W in the case of classic stereo use, or 4 x 200 W in the case of a four-speaker system, peaks at 2 x 400 W in BTL mode and greatly modifies the sound, even with loudspeakers, without the need for a large power load.
As well as trying out this mode at our leisure with several models, our tests also focused on the bi-amplification of two- and three-way speakers. However, we had already returned the super-tweeters tested in the previous magazine and were unable to retrieve them to measure the amplifier’s capabilities in the extreme high register to the maximum, which would have been all the more exciting to check as they are particularly well suited to the Zu loudspeakers in our possession.
Mainly connected to digital sources, the ROSE was also compared on its phono input to stand-alone preamps, themselves connected to our Linn LP12 turntable and to the Vertere MG-1 MkII, also tested in this issue.
The sound of the HIFI ROSE RA180
The scent of ROSE is what immediately springs to mind when listening to this amplifier, whose sound seems to permeate the room like incense. With a conventional connection, what strikes you immediately is the smoothness and naturalness of the amplification. If you didn’t know better, the HIFI ROSE RA180 could be perceived as a pure Class A product rather than a Class AD hybrid. Vigorous, the energy provided is never violent, but just comfortable enough to energise a large number of loudspeakers, even very demanding ones. Warm, the timbres emerge with clarity across the entire spectrum through a very airy soundstage, wider than it is deep, but with a well-balanced overall breadth, with no disparity in treatment between the different elements.
In BTL mode, all the aforementioned components gain even more, and the warmth described above becomes thicker, while the soundstage seems to gain even more space, the power now at 400 W per channel allowing a real gain in attacks, initially round and now more clearly defined. The typicality of the sound doesn’t change, but everything opens up and improves to move this amplifier into another category, from which the competition initially found in stereo mode in this price range now seems to be moving away with the addition of the BTL. The same is true of the internal phono preamp, which is widely competitive with products priced at around €1,000, and against which we had to connect the Aurorasound Vida MkII preamp – priced almost the same as the amplifier – to truly surpass the phono quality of the RA180.
In the case of bi-amplification, the sound attracts in the same way as in BTL mode, and with a two-way loudspeaker, the difference between these two types of connection didn’t seem so glaring to us, since BTL already contributes so much compared to the classic stereo connection. On the other hand, on a very top-of-the-range three-way speaker, the high-frequency range was further extended and, at the same time, the whole quality of the image was refined, not only in the purity of the timbre, but also in the depth of its definition.
Our conclusion
The HiFi ROSE RA180 is attractive not only for its looks and modularity, but also for its class AD sound, which has nothing to envy to the warmth of many class AB or even class A amplifiers. Warm and powerful, with already very high levels of noise reduction and damping factor, it displays all its superb qualities when used in BTL mode, where a single pair of speakers is carried away with almost no limit to the width of its frequency band and the breadth of its dynamics.
Having succeeded in breaking into high-fidelity with innovative sources, HiFi ROSE is continuing its pioneering work with amplification, giving pride of place to digital technology. So far, so good!
Author: Vincent Guillemin
Technical sheet: HIFI ROSE RA180
- Origin: South Korea
- Price: € 5.990
- Dimensions: 430 x 391 x 130 mm
- Weight: 16.7 kg
- Amplification type: Class A/D
- Power rating:
- 4 x 200 W at 4 ohms
- 4 x 200 W at 8 ohms
- 2 x 400 W in BTL mode
- Impedance: 44 kΩ (XLR) ; 47 kΩ (RCA ; Phono MM/MC)
- Harmonic distortion: 0,006 % (50 W)
- Signal-to-noise ratio: 108 dB (XLR) ; 106 dB (RCA) ; 79 dB (Phono MM)
- Frequency response: 10 Hz – 90 kHz
- Analogue inputs: 3 x RCA ; 1 x XLR ; 1 x RCA Phono
