Test tube amp Westend Audio Monaco Mk2: delicate pleasure with plenty of power

Tube amplifiers are no longer what they used to be. And that’s a good thing. Tube amplifiers in the past: built like something out of a hobby store, operational reliability as good as hell, performance subterranean. Tube amplifiers today: built like a fortress, highly reliable and durable thanks to microprocessor control, decent performance even for notoriously demanding speakers. Just like the Westend Audio Monaco, the first edition of which was praised by LowBeats. And whose second edition, the Westend Audio Monaco Mk2, is now up for testing here: weighing in at a whopping 46 kilograms and with 47 centimeters from left to right, it is also suitably wide-legged. The test by LowBeats author Lothar Brandt.

Everything is so colorful here: the Westend Audio Monaco MK2 remains individual

Developed and manufactured in Germany – and with a correspondingly self-confident price tag. In powder-coated black, the price tag is 24,000 euros, in white with polished aluminum applications 25,000 euros, nickel-plated (definitely worth a look, cool) 27,000 euros. And if you’ve always had a slightly decadent penchant for oligarchic hi-fi, you can also order a version with 24-carat gold plating – for 40,000 euros. But that’s just by the way. Even the standard versions are of the finest build quality and have nothing to hide. For our Swiss readers: The well-stocked high-end dealers at Aug & Ohr in Zurich have spontaneously added the Westend Audio Monaco Mk2 to their portfolio and are offering it from 25,900 Swiss francs. And then all the customs fuss is taken care of.

2:1

The basic cabinet design with its multi-layer structure, round-tower reinforced transformers and upstream tube octet has not changed in the Mk2 compared to the Mk1. What has changed from the first to the second generation is the resonance optimization of the housing. The fact that this is not L’art pour L’art will be obvious to anyone who knows about the sensitivity of glass pistons to microphonics. The brains behind Westend Audio, managing director Stefan Trog and developer Günter Mania, put a lot of effort into keeping these and the other components from vibrating.

Even if it is not visible from the outside. All bolts in the housing are now braced with silicone rings. What is more visible from the outside: The thin intermediate ribs between the layers are no longer made of aluminum, but of wood. It’s not just Soulnote’s highly acclaimed components with their rattling lids that show just how big an impact the mechanics can have on the sound of the devices. And so Trog’s search for the best material for the intermediate ribs was not a short one. After lengthy trials, solid wood was ruled out, as was MDF – both took too much energy out of the sound. Only the special HDF now used provided the right mix of damping and energy

The rock-solid basis

The real dream came true with the Mk1. Günter Mania, a developer who is actually known in German high-end countries as a transistor maniac (please forgive the pun), helped realize it. Since the 1980s, he has launched a series of affordable, powerful-sounding and reliable transistor amps for the Baden-based company AVM. Even today, his development work is still firmly rooted in semiconductor technology. As a measurement engineer (AVM was originally shortened to audio-video measurement technology), he remained averse to tubes for decades. Until he discovered that they were equal or even superior in terms of sound quality – and developed a great deal of ambition to ensure that the glass bulbs also had adequate operational reliability.

Westend Audio has given its play leg the space it needs to program microprocessors, revise and refine the circuitry for the design of the oversized switching power supply. The highly efficient converters of mains voltage into useful voltage are no longer at a fundamental disadvantage compared to their linear competitors. We may be able to go into this in more detail in a later LowBeats test. Suffice it to say with a former chancellor: it’s what comes out the back that counts. And with the Westend Audio Monaco Mk2, that’s quite a lot. Speaking of going into more detail: Our colleague Holger Biermann has already explained a lot about the device in detail in his review of the Mk1 and backed it up with quotes. We don’t need to repeat all that here. This gives us the opportunity to go into a little more detail here.

A little tube lore

So let’s take a brief detour into the world of tubes: A tube of the simplest design, the diode, has two electrical parts (electrodes): The heatable cathode and the anode. If an electrical voltage is applied (negative to the cathode, positive to the anode), a current flows from the cathode to the anode. In the triode, the third electrode is the control grid, whose grid voltage can be used to regulate the anode current without power. In high fidelity, triodes have mostly made a career as double triodes such as the 6SN7, its quasi-successors ECC 81, ECC 83 or the ECC 82 used here in the Monaco Mk2 in the input and driver/phase shifter stages. The 300B is also famous as a power triode. In the tetrode, a fourth electrode, the screen grid, is added between the control grid and the anode. The name shielding grid comes from the fact that this positively charged grid shields the control grid from the anode. Tetrodes can achieve significantly higher gains than triodes. So-called secondary electrons can cause problems. Pentodes try to put a stop to these with the fifth electrode, the brake grid. For cost reasons, beam power tetrodes or beam pentodes use bent electron beam guide plates instead of brake grids. For audio applications, developers usually use the EL34 pentodes or the 6L6, 6550/KT88 beam pentodes/tetrodes as well as derivatives and significantly more powerful further developments of these. Like the KT 150 of the Octave RE 320 stereo tube power amplifier recently tested here.

The special end tube

The Monaco goes its own way here. Trog and Mania wanted power, i.e. voltage times current. And both stable and sufficient, even if the loudspeakers or their crossovers in relevant frequency ranges with outrageously low impedance or adventurous phase rotations challenge the current delivery capacity of the naturally rather voltage-friendly pistons. The two came up with a power tube that is rarely found in the high-fidelity environment, at least in this country. The E130L is a genuine pentode, in which the control and screen grids are designed as tension grids. Without going any deeper into the fascinating technology of the pistons: Tension grids are designed to minimize the dreaded series dispersion and ensure very linear amplification. Many, unfortunately all too many tubes, even those from recent production, exhibit extremely high scattering of their data. Employees of hi-fi manufacturers who “match” two tubes from normal series production for a particular amplifier to create suitable pairs know a thing or two about this.

Its linear amplification and the high steepness of its characteristic curve quickly paved the way for the E130L to be used in audio push-pull power amplifiers – in addition to applications in ultrasound diagnostics or for voltage stabilization in the power supply units of sensitive measuring devices. The E130L is said to be able to handle up to 1.5 amperes peak current. Which is simply phenomenal for a power tube of this size. Tight series tolerance, plenty of current, extremely linear: these are ideal conditions for power tubes in high fidelity, especially when they work in push-pull mode in pairs per channel, as in the Monaco. The only problem is that they are probably not so easy to manufacture and therefore very expensive – and scarce on the market. As far as the author knows, only Western Electric in the USA officially builds the 7534 – and only for the military. According to their own statement, Westend Audio are the only licensed users in the hi-fi sector.

Processing and operation: top

Let’s leave it at that. And let’s take a look at the periphery of the wonder bags. First of all, there are the sockets, which make an excellent impression. A look inside reveals a well thought-out architecture for a considerable amount of components, including the aforementioned processors in the form of integrated circuits. However, these automate numerous safety functions and sound enhancement measures such as automatic bias adjustment. And last but not least, the full-metal remote control, which sits comfortably in the hand, enables the transfer of commands.

To be honest, however, you also like to put your hand on the three control elements on the front, whose highly refined surfaces already give a haptic promise for the things that are coming acoustically. The central volume control with mute at the touch of a button is not a conventional motorized potentiometer, but functions as a so-called incremental encoder for an IC-based network. And that in two level steps, depending on how fast you turn it. You have to experience it. In any case, it feels fantastic. When you look at the back, you almost regret that the device normally only offers you the front view. You would also wish for such a quality of workmanship for all connections from some of the more expensive competitors. You wouldn’t necessarily have expected a USB socket: However, this is by no means used as an interface to a secretly internally installed DAC department (in the high-end, this should be connected to the source and not in the amplifier anyway), but for connecting an external display, for example. And of course – we are in the digital age after all – for updating the software used internally. Which, incidentally, can also control the color and brightness of its own front lighting.

The indication of the correct or incorrect phase when connecting to the mains deserves huge praise, because it is incomprehensibly still not a matter of course at the high-end. Here, the user immediately recognizes whether the mains plug has been plugged in “the right way round”. The operating instructions for the numerous functions in the main and sub-menus are exemplary. Some other tube amplifier manufacturers (and not only them) could take a leaf out of their book.

Sound and performance: also top

As a self-confessed vinyl lover, the author was briefly annoyed by the lack of a phono input, or rather the lack of an option for one. The slight resentment vanished immediately when the Monaco (Italian for Munich, by the way) Mk2 played in the LowBeats listening room in the aforementioned Munich. Then with exquisite digital material fed to it by the CD/SACD player or the in-house streamer. From the very beginning, there was a naturalness and ease at play that characterizes good tube amplifiers. And there was also a sovereignty and stability, even at really high volumes, that would have been more likely to be found in the transistor camp if eight glass bulbs had not glowed completely unmoved on the Monaco’s wing. The author, however, always starts his listening tests on quiet soles – his hearing, like all of ours, would quickly “close up” to the most delicate details if he were to listen at full blast. But no matter what kind of tender melodiousness he was looking for, the tester got his money’s worth with a string sextet by Brahms as well as with wondrous tunes by the Weather Station group. Without being overloaded with overly sweet sound calories, rather delicate nuances spun him in, so to speak. A few hours of listening later, April Wine drummer Jerry Mercer delivered the final blow. Sure, the accompanying record is called “Harder Faster”, but the Canadian band doesn’t just bludgeon away, it offers beautiful melodic rock. “Say Hello” is an exceptionally strong track where Mercer and co. lay down a fantastic groove. And the Monaco Mk2 added plenty of fire. Even when power-hungry transducers like a Fink Team Borg were connected to the speaker terminals. That had bite!

And how much better than the Mk1 version is the new one? Trog had kept back an earlier Monaco for us especially for this test before the complete overhaul. This gave us enough time to hear the differences. But we didn’t need it, because the differences were immediately obvious. In fact, the sonic gain over the Mk1 is astonishingly large. Fine details came more naturally and noticeably “lighter” with the Mk2 version. The new Monaco drew the individual instruments even more precisely, played with a bit more body and also opened up the room in all dimensions. No matter what measures the Trog/Mania team came up with for their Mk2 version: They all work and make the new model sound much more mature and open.

Conclusion

With the Mk2 edition of its Monaco integrated tube amplifier, Westend Audio has once again made significant progress. While the Mk1 was already no slouch in terms of power and power of design, the successor has stepped up a gear in terms of finesse and accuracy. In itself, the Westend Audio Monaco Mk2 is a superbly crafted, technically excellent and sonically inspiring integrated amplifier and thus remains LowBeat’s reference integrated amplifier. The fact that the Monaco has become 4,000 euros more expensive as a result of the upgrade and over the last four years naturally makes hi-fi fans swallow a little. But what you are buying here is not only an excellent-sounding 100 watts per channel, but also the good feeling of having made a good investment for life. By the way: For all those who want to see or hear the Monaco MK2, there may be a great opportunity at the HiFi Tage Darmstadt (October 19/20). Where? Room 3.08 Neon.

Westend Audio Monaco MK-2	2024/10
REFERENCE

Rating

Sound Quality Usability Workmanship Quality Rating

The rating always refers to the respective price category.

	Outstandingly lively and natural sound
	High precision, very good control
	2 x 100 watts and stability up to 2 ohms
	Outstanding workmanship, wide variety of surfaces

Distribution:
ATR Audio-Trade
Villa Belvedere
Walluferstr. 2
65343 Eltville am Rhein
www.audiotra.de

Price (manufacturer’s recommendation):
Westend Audio Monaco MK2: from 24,000 euros
Enclosure variants on request

Technical data

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