 Rogue Audio is one of the few American companies manufacturing tube amplifiers, that apparently survived the Chinese invasion with full health and beauty, without outsourcing production outside the USA, where it comes from, to overseas sources of cheap work force – Taiwan or China. This is quite an achievement, especially, when we take into account, that Rogue was mostly known from their more expensive products, and now, in the form of the Atlas series, proposes a range of incredibly affordable, hand made in the US, devices. This is a sensation, but it shows that it can be done, when there is a will to do it. And when you have a conception. Because I have tested the products of that company – the integrated amplifier Cronus in Audio, and in HFOL the gramophone preamplifier Stealth, so I was more or less prepared for testing the M-150. Actually those power amplifiers were the company's icon for me, since I learned to know it. For some reason their shape just “fits” me, and I like them very much. Also the concept behind the mechanical construction, shared by Ongaku from Audio Note, as well as their proportions – all this appeals to my sense of aesthetics and technical subconsciousness. SOUND )
When one of the owners of an audio shop, knowing I am testing the M-150, asked me how they sound, and described the situation in a few military words, he was surprised: “It means it does not sound as a KT88? It is not quick and even chilly?” Then I was surprised. And so surprised we did separate (or rather we disconnected - I have just read the novel – my promoter did not like me to use the word “book”, as every piece of literature is a kind of book, a novel, an essay, a story – of Steven King “Cell”, so I try to keep my conversations as short as possible...). The KT88 tube never sounded chilly to me. Just the opposite – both in new as well as older McIntosh constructions (like the MC275 Commemorative Edition), earlier tested amplifier Melody SP9, and in other, expensive and cheap KT88 designs (like Unison Research) always sounded a bit warm – incredibly vivid, dynamic, but never cold. Different are constructions based on 6550 tubes. This “industry” version of the KT88 is cleaner, more precise, but does not have the midrange appeal of the latter. That is why I was surprised. Especially as i was after first listening sessions of the M-150 and it clearly belonged to the KT88 family. In case of this amplifier we have the ability to influence the sound to some extent, as we can choose between the triode and ultralinear setting. The distributor stated that he always listens to the M-150 in the first mode. My experience with the Manley devices, for example the powerful amplifiers Neo-Classic M-250, but also the smaller power amps Mahi, I tested for Audio (2/07) – bot have the ability to be switched from triode to pentode in their case – comes to the conclusion that in the triode mode the pentodes (like EL34) and tetrodes (like KT88) sound more pleasant, are characterized by better timbres on the midrange, but in the ultralinear mode are more precise and have better resolution. It is the same with the Rogue Audio M-150. This is obviously a question of personal preference, and the system, but with precise speakers, and the Marcus and Dobermann of Harpia Acoustics are just that, for me the ultralinear mode was the better choice. Not that I would not value timbre – in contrary, I am addicted to it, and when I meet a splendid device like DC-1 Audionemesis or JD1 MkII/JS1 MkIII Jadis, then even if those aren't masters of the resolution, I'm in. The basis is that the resolution must be at least very good – not brilliant, but just enough. The M-150 is part of this exclusive group.. )
It can be different with audio devices – some show their capabilities from the very beginning and pull us into their world, other make us wait, because when those are different from what we were listening to before them, then we have to “purify” ourselves before listening, get rid of any prejudice. There are of course also devices that don't “fit” us – due to not all to good sound, not matching our system, or due to one characteristic that annoys the listener and covers all other aspects of the sound. Starting with the first tact of the piece “Fancy Robot” from the discs Soft Rock - Justine Electra (City Slang/Sonic Records SLANG1037982-2, promo copy CD-R) and we know, that the Rogue Audio power amplifiers belong to the first described group. This recording confirms the previous diagnosis: the amplifier plays with a strong, juicy sound with low bass and a slightly tamed attack. Those characteristics are more pronounced in the triode mode, where a slight withdrawal of the upper midrange and rounding on the bass can be heard. This gives a nice, easily accepted sound, especially with the more commercial discs, just like the mentioned Soft Rock. Switching to ultralinear mode improves bass control and rises a little the level of the upper treble. And though maybe the timbre is not as vivid as in triode mode, but without question the sound is for me more correct. In this setting the resolution of the device is much better. The vocals in triode are slightly pushed to front, a bit larger and seemingly more articulated, but this is just an illusion, in reality their structure and texture is not very clear. For me, cooperating with the Lektor Prime Ancient Audio and Wadia 27ix (test in this issue of HFOL), in the ultralinear mode the M-150 sounded better, because they presented themselves as very thorough power amps with a very good timbre and a splendid bass control. )
From the side of even tonal balance the M-150 showed itself also on the, referential for me, disc of Adam Makowicz – Unit (Polskie Nagrania, PNCD 935, Polish Jazz vol.35, CD). The midrange in the moments, when the Fender piano is playing, is maybe not as resolved as from the Leben CS-300, but frankly speaking not many devices from this price range (if any) can reach to it in that aspect. But the treble, I'll be damned, was better in the M-150. The ability to display the details and edges was on comparable level, but the Rogue was able to show the differences in weights of the brass better, their “physicality”. This is probably the result of the mentioned earlier swing in showing the scale of instruments, here having the supplementation of very real brass. Also the other end of the frequency scale, the bass is brilliant. In “War Song” from the Makowicz disc, with the strong base drum beat Rogue just run over the weak Leben. At least with the Dobermann. With the Marcus, a high effectiveness speaker (92dB) it was a bit different, but even there the extra bass control on the lower bass was helpful. This all was while connecting the M-150 input to a variable output (or better said integrated preamplifier) of the Prime player or the Wadia DAC output. When we connect a preamplifier, some of the instrument separation disappears. The midrange will be shown more dynamically, but the amplifier's transparency disappears somewhere. The M-150 will have to be adjusted for the given preamp. With the Manley Wave, the American amplifier sounded much better in triode mode, although the treble was laid back and not as accurate as earlier. So it seems that the M-150 should work without a preamp. And it is not always so, as you can recall the phenomenal power amplifier Accuphase A-45 without an external preamplifier, connected directly to the Prime, would not “sing” at all. Also the sound stage, earlier deep and clear, with a preamplifier was a bit shallower, with a stronger showing of the first plane. This, however, can be a very nice proposition – maybe not fully neutral, but very nice sounding, and when we search for relief in music, emotion or timbre, then maybe a preamplifier can be the best solution. But if we want to exploit all the abilities of the M-150, and those are really significant, the we should hook them up to a player with variable output, preferably Lektor Prime, with which it sounded terrific. DESCRIPTION )
The M-150 amplifiers are set up as mono blocks. Both present themselves splendidly, at least that is my opinion, mainly by keeping good proportions. If we take some measure as one unit then the amplifier will have 5 units of depth, two height units and three and a half width. Moreover the amplifier's body was split in a 3:2 ratio, where the three units is the front part, covered with iron plating, and the two are openwork covered tubes. The front panel is made from thick aluminum, with deeply carved (cut?) company logo. In the middle we have a round hollow with an aluminum power button and a blue LED. The high enclosure in the front covers the transformers – mains and output. Both are very large and additionally shielded with metal winding covers. Below the metal bars in the rear (the cage can be removed easily, but with it the device looks very well) the tubes were placed, together with a meter used for calibration. Due to that unusual arrangement of components, opposite to the usually used, the signal from the inputs runs by a short connection straight to the input valve. On the other hand the signal from the output transformer can run over a longer path, as it has a much higher level. The input tube is a double triode 12AX7, and the output tube drivers are also double triodes but the 12AU7. As standard equipment with the amplifier come Sovtek tubes (12AX7 are the very good NOS 12AX7LPS – Large Plate), but the distributor went lengths ahead and populates the amplifier with Mullard tubes. In the output stage four tetrodes KT88EH of Electro-Harmonics are employed, two pairs per channel in the push-pull setting. On the back plate we have a IEC power connector, unbalanced RCA and balanced XLR inputs, a switch to chose the output tube mode (ultralinear or triode) and two pairs of speaker terminals for 4 and 8Ω. )
After unscrewing the top cover it turns out, that the transformers are not only big, but they are screwed to a large and thick aluminum plate, and only that plate is screwed to the bottom of the enclosure. The circuit is locate on one big PCB. It seems to be a balanced setup, as we can distinguish a symmetrizing transformer Jensen JT-11P-1HPC with a wide frequency range (up to 80kHz) and low distortion, meant for the RCA input. Besides it, in the circuit splendid passive elements were used, like Dale resistors, for coupling the output tubes polypropylene capacitors Mcap from Mundorf. It is a pity, that the low power tubes are coupled by run of the mill foil capacitors.
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