SWISSONOR  AM

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What they say ...

 

 

Fidelity Online (Germany)

by ROLAND KRAFT | February 28, 2016

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The word "modular" (as in in Amplificateur Modulaire) is to be understood here as meaning that an amplifier set is put together in a customer-specific manner and built into a heavy non-magnetic cast frame. The AM6441 is - and this explains the cryptic name - made up of a power supply unit called AM1, two single-ended 300B power amplifiers called AM4, and a matching phono stage AM6, which has two phono MC and three high-level inputs. Instead of the phono stage, a module with a passive high-level pre-stage (AM5) could also be used. So, with the help of the preamp modules, the 300B and its power supply unit become an integrated amplifier.
 

Each of the modules is built on a five millimeter thick aluminum plate, which is resiliently decoupled and sits in the cast frame with rather massive screws ... sheer mass is the guarantee that neither transformer nor electrolytic capacitor vibrations can spread. Even the tube sockets are mounted with rubber bearings, which experience has shown to be one of the best recipes for combating microphonic problems. If you look very closely, you will also discover that the mains transformer and transformer are not simply screwed directly onto the chassis, but rather mounted in isolation, one of the many little secrets of hum-free design (transformers should only have ground or earth contact at one point or screw).

 

And because the topic is so important, especially when working in a team with "loud" speakers, let's stick with the "signal-to-noise ratio" - the so-called signal-to-noise ratio. In this regard, the Swissonor is awe-inspiring. Even with a 96 dB loudspeaker, not the slightest hum can be heard, not even with the level control fully turned up in Phono-MC mode ! In addition, there is extremely low residual noise. Wish everyone would imitate the Swiss !

 

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Pre-stage instead of Phono Stage

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Incidentally, the term “phono stage” doesn't quite apply to the AM6 : Rather, it is a complete preamplifier, the inputs of which are all switched via relays directly on the socket panel. Two pairs of phono sockets can also be selected via a switch, fine Hashimoto transformers are used in the MC version before a phono stage built in the style of the legendary Marantz 7 circuit takes over the RIAA equalization.

 

Obviously responsible for this are first-class double triodes ECC803S (JJ) and a 12AX7WS from Sovtek. The Hashimoto SUT is optionally available in three versions, one of which is ideally suited for low-resistance, "quiet" SPU-type cartridges. An MM input is of course also possible as an option. Below deck there is - perhaps contrary to the expectations of this machine - no point-to-point wiring, but rather circuit boards with zinc / gold conductor tracks, which are processed using Cardas silver solder. Stabilized anode voltage and regulated heating voltages are a matter of course, as are excellent components, such as lots of Mundorf capacities. The connection to the power amplifier wing is “underground”, which means that the input sockets of the two 300B modules remain idle.

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The Path to Full Music

 

The two mighty 300Bs immediately catch your eye - these are 300B / n by "Full Music" from TJ with mesh anodes and "pear" glass bulbs ... magnificent pieces that are controlled by a 12BZ7. And yes, admittedly, Western 300Bs cannot keep up with that in terms of purely aesthetic technology.

 

Urs Frei opted for a so-called "μ-follower" circuit for the 12BZ7 driver stage, which guarantees low distortion, high bandwidth and low output impedance. This technology is by no means found every day in mass-produced single-ended devices ... As far as the transformer is concerned, the Swiss relies on a nine-fold nested winding on an M102 core, consequently only equipped with a secondary winding. In plain language this means that only an eight-ohm tap is available on the loudspeaker side, other impedances can be ordered at no extra charge. This is consistent, because output transformers with several secondary taps are by no means better, but are subject to compromises.

 

The well-known critical direct heating of the 300B received a similar amount of attention. Here, a discretely constructed direct voltage heating regulated by Darlington transistors is used. The anode voltage for the driver section is also regulated, the heating voltage is also stabilized - electronically, this is a "modern" approach to a 300B amp, quite in contrast to the numerous retro concepts whose representatives, for example, outlaw voltage stabilization as pure blasphemy. Experience has shown, however, that one shouldn't make religion out of the different approaches straight away, but consider the individual case.

 

A largely undisputed audiophile commonality are of course whole batteries of high-quality polypropylene capacitors at critical points of the amplifier train, and in this regard the Swissonor tube amp is no exception. Incidentally, often unjustifiably highly praised retro components cannot be found in the amp. Except for the beautiful black "Chickenhead" knobs, yes! 

 

 

New Fashion?

 

Despite the newfangled control technology, the AM1 supply module contains a good old transformer with five secondary windings, a rectifier tube of the type 5U4G and a bulky, encapsulated 14 Henry sieve coil together with a Mundorf “tube cap” as a charging capacitor. The CLC filtering in the power supply unit (it consists of high-quality, temperature-resistant electrolytic capacitors with a long service life) is once again supported in the respective modules by film capacitors. To “fiddle” with the type 5U4G tube used “for subjective reasons” - as the Swiss put it - would not be a good idea; less powerful rectifiers might have problems supplying the powerful device. The "Ground Lift" switch on the back of the power supply module also serves to eliminate residual hum, but is not really used much in practice. 
 

 

Subjective impressions

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With regard to the Swissonor “construction quality”, let me perhaps add a few more subjective impressions ... no, not yet about the sound, but rather about the way in which this device - not only for me - was received. Here you have that seldom occurring feeling of correctness, of absolutely trustworthy solidity and a price-performance ratio that allows the work of art and the customer to go home satisfied with each other. The whole design of this extremely impressive amplifier speaks for itself. For example, the chassis is more reminiscent of mechanical engineering than of entertainment electronics.

 

And, by the way, a measurement, test and equipment protocol that is probably drawn up with typical Swiss meticulousness also contributes to the overall impression : The document “Control final and configuration de l'appareil SE 300B” is signed and enclosed with the “apparatus”.

 

However, one thing I have so far wrongly withheld from you : In the meantime, Swissonor also offers small cast chassis for individual (preamplifier) ​​modules. In addition to the amp, we also had the passive “transformer preamp” AM5 available, which is equipped with a set of relay-controlled high-level inputs, two step-up transformers and a level controller. With a choice of plus three or plus nine decibels gain factor on the transformers, I was immediately impressed by this little passive solution, because somehow the story "locked" in place immediately, when working as a team with an AcousticPlan DAC, the unbelievable Einstein phono preamp and various tubes - No eye stayed dry for power amplifiers. More is not yet revealed, because the Swissonor AM5 undoubtedly deserves its own story.

 

... Now, back to the 300B integrated amplifier, on which the loudspeaker connections still deserve a mention : Insulated banana sockets instead of fashionable fat pole terminals, is the understatement motto - with which I deeply agree. With proper banana plugs, perfect electrical contact is guaranteed, and the annoying terminal fiddling is no longer necessary. Sure, real tweaks like to choke monstrous welding clamps with the pliers (and finally off), but sound improvements are definitely not achievable in this way. That should put an end to the complaint, because I have nothing to criticize about the amplifier. Or maybe I do ... namely, the fact that this beautiful piece will be delivered to its new owner in the next few days ... and unfortunately it is not me.

 

Therefore, do not regard the following as judgmental - because a place on the winner's podium is already certain - but rather as simply descriptive : 

I like to roughly divide such amps into two categories :

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• Casual, rather muscular “gliders” who nonchalantly ignore one or the other tiny detail ...

• ... and more meticulous "gentlemen" who indulge in delicate, almost floating sound webs with relish (sorry, if I'm prosaic become).

 

The Swissonor is more of the latter, clearly pointing in the clear, slim direction, but without the skeleton becoming immediately visible. Its vocal presentation is opulent, colorful and wonderfully focused and devoted to the finest accents in front of a horizon-wide spatial background - so fascinating, so detached and so tangible, as one could wish.

 

This amplifier exhibits a thoroughly “audiophile” precision, which would normally not be ascribed to a 300B... a precision accompanied with unusual intensity and speed, with light-footed, springy dynamics ... instead of massive, large-caliber ones.

 

 

Magical potential

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This sound also has magical potential, appears completely natural, timeless, and it pulls the listener under its spell without immediately waving the candy bowl. The Swiss construction remains as supple as oiled silk. The performance comes across with a "perfectionistic" touch in places, has enough radiance and tension, and  does not lose - as is so often the case - intensity and speed.

 

Even with whisper-quiet passages, this amp can still play touchingly, the picture even gets wider and deeper, no definition is lost. The focused connoisseur learns to ultimately appreciate the silence more than the storm ...

 

But for all of this, you really need a "real" loudspeaker which reacts without delay to the slightest touch of electrical voltage ... the use of such a speakers with the Swissonor will negate any "old experiences and prejudices" one may have had.

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LP Magazin (Germany)

by HOLGER BARSKE | Issue # 3, 2011

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Who invented it? The Swiss, of course. In this specific case, Urs Frei from Swiss company Swissonor, a small but fine manufacturer located in Geneva region, not far from the French border. Initially active as supplier, they developed and produced a non magnetic cast iron platter for another ancient familiar Swiss product, the legendary friction-wheel driven Thorens TD124. To follow-up the sustained demand, a specific company for spare- and upgrade parts and other special equipment was founded.

 

Concept

 

This effort resulted in a worldwide unique amplifier concept in full tube design, the “AM System”. The base is a support frame receiving four modules, building an integrated amplifier tailored for individual needs. Actually, there are six modules available :

• The power block AM1 constitutes the basic operating element, available in power-amplifier-specific. There is a choice of four power amplifier modules : 

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• The component under test in this issue contains a pair of the most powerful module named AM-2, based on a 6V6 in push-pull, which provides 10 Watts per channel in an exclusive way.

• Alternatively, the customer can choose the single-ended AM-3 based on the 6B4G tube, a close cousin to the well known 2A3, and offering 3.6 Watts per channel.

• The third module named AM-4 is based on the “inevitable ”300B", with an output power or 8W.

• And finally, the AM-X which sports the PX25 tube delivering 6W.

 

As for the preamplifier module, there is some choice here as well.

• The AM-5 module is a purely passive transformer preamplifier for line sources exclusively ...

• And the AM-6 has a configurable full-tube MM phono stage with two phono and three line inputs. Optional Hashimoto SUT for MC are available.

 

 

The AM 6221

 

Our test component's name is the “AM6221”, the number indicates use of one power pack (1x AM-1), two push-pull 6V6 power amplifiers (2x AM-2) and the one MM/MC phono preamplifier (1x AM-6). Our phono preamp is configured with one MM input and a MC input using the optional Hashimoto HM-3 MC SUT transformers.

 

Adding all these modules and options to the "package", the final price adds uo to about 11’000 EUR. Not cheap, but this is real Swiss handcraft and is not available everywhere.

 

Let’s begin by looking at the chassis frame design : This is nothing less than a "complex casting" out of a non-magnetic cast iron alloy. The cost / investment parameters of this approach are very different from screwing together a number of metal sheets ... very ! On this "lead-like" heavy support, the modules are screwed whilst respecting careful decoupling requirements.

 

The power block module is basically situated on the right hand side of the chassis' frame. The solid power transformer, individually decoupled and damped, has five secondary windings delivering the raw voltages, where the high voltage is rectified by a tube (here a GZ34), is then filtered by a massive choke (the second heavy transformer-like block on the AM-1 plate), and by-passed by a special Mundorf foil capacitor. The power supply rails for driver and preamp are separately stabilised and filtered. Even the heater current supplies enjoy separate electronic "attention".

 

This is definitely a luxury concept, and can only in very few aspects be viewed as a Vintage design. Rather, this is a most modern amplifier solution.

 

The power amplifier is a feedback-free design based on the sturdy 6V6 tube, a tube that is less demanding on loudspeaker performance than the three single-ended designs. The manufacturer recommends the use of loudspeakers with an efficiency of 92 dB (1W) and higher, but our experience proved that far lower efficiencies are possible too. Notably, such efficient loudspeakers can be found in Swissonor's product portfolio (Swissonor B.A.C.H. Series).

 

Thanks to the highly sensitive power tube, the amplifier is electrically “short”, needing only one ECC81 double triode type as phase splitter and driver. An alternative variant uses the ECC88S (with 4 dB less gain).

 

The output stage works in ultra-linear mode, and the output transformer with its 14 windings is a real piece of splendour. As with all other modules, a gold-plated PCB constitutes the base of the electrical circuit. The AM-6 RIAA module hosts a phono preamplifier based on the good old Marantz Model 7 circuit, making use of three ECC83 double triode tubes. The phono section’s 43 dB gain is comfortable for all moving magnet cartridges, while a pair of Hashimoto step-up transformers bring the additional gain required for low output cartridges. Swissonor offers a choice of three SUTs : HM-3, HM-X and HM-7.

 

Genuine chicken-head knobs serve as input switch and volume control on the module’s top plate. The placement of all input sockets on the top is a fine choice and facilitates largely the setup’s cabling. As partners for this system setup, we selected a pair of loudspeakers which promised a trouble-free match for the amplifier. The “Coco 15” employs a coaxial driver issued from professional public address market and allows an efficiency of about 96 dB. As safe value for use with the HM step-uptransformers, a Miyabi-based MFSL C3.5 delivered the input signal.

 

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Sonic Palette

 

Both choices proved to be a perfect match, and the result was totally in a class of its own. Paul Wilbur Klipsch (the famous loudspeaker designer) once said : “The midrange is where we live”, and he was completely right. The Swissonor amplifier delivers an incredibly clear, clean, free flowing midrange that dominates the action in such an energetically and sovereign manner that the rest of the spectrum apparently takes a rear seat.

 

I recommend an audition with Nina Simone’s fantastic Carnegie Hall Concert. Thanks to this setup, the listener is involved in such an intense manner, that he gets shivers. Fortunately, there is no absolute need for such extreme speakers to get that incredibly vivid and emotional sound. The Swissonor amp -- as a temporary replacement for The Quad II Classic integrated amp -- drove the Progressive Audio Diablo ... and lo and behold - this combo works, too. The Quad acts somewhat larger and more eased-up at the extremities of the spectrum, but does not offer the same measure of unique clarity and expression.

 

Additionally, the Swissonor amplifier throws an extremely well structured and clean image ... and its low noise level does the rest. Even at full-tilt volume, there’s only a slightly perceptible noise level – a quality much appreciated when using the MC phono input. This is certainly not an amplifier for heavy metal freaks ... if you favor this genre, please stay away ... but for voice, instrumental aficionados who primarily enjoy Classical, Jazz, 70's Rock and Folk, there’s hardly a more impressive solution.