music, and this is the pattern that sounds musically consistent and consonant to our ears.
The Plinius engineers realize that it is actually amusically counterproductive to only concentrate on reducing every kind of distortion individually, as most other solid state amplifiers do, since that leaves behind only higher odd order distortions, which make those other solid state amplifiers sound artificial. They realize that, instead, it's important to work on the whole distortion picture, not just individual parts, since it is the whole picture that determines the transfer characteristic, which in turn affects the amplifier's sonic personality, even at ordinary listening levels.
The Plinius engineers realize that, when negative feedback is employed to reduce total overall distortion, this feedback actually creates new greater levels of higher order distortion, even at ordinary listening levels. And here comes perhaps the most dramatic conceptual break (and breakthrough) of the Plinius engineers, contrasting them from their counterparts designing competing solid state amplifiers. The Plinius engineers realize that, if they are to obtain the natural musicality of a declining progression of the transfer characteristic (which gives an amplifier its sonic personality), then it is their responsibility to design the circuit transfer characteristic to actually retain judicious proportions of the low order byproducts, especially to counterbalance new higher order byproducts introduced by the feedback, even at quiet or ordinary listening levels.
The engineers designing most other solid state amplifiers are so single mindedly hell bent on reducing total overall distortion, and every individual kind of distortion (e.g. all even order), as much as possible (by whatever means) that they neglect to pay any attention to the progression of orders of byproducts that remain, the progression that indicates what the amplifier's true transfer characteristic is, and therefore what the amplifier's sonic personality is, as imposed on all the music, at all listening levels. So this progression in these other amplifiers is totally skewed, being dominated by higher odd orders, which sound artificially ugly and which are in complete opposition to the natural progression, wherein lower orders dominate, and wherein even order byproducts (especially the lower even orders: 2nd, 4th) are richly represented.
The Plinius engineers also realize that symmetrical solid state circuits don't truly work in eliminating even order distortions, and that for musical naturalness you don't even want to totally eliminate all even order distortions in the first place, so it would be counterproductive to employ symmetrical circuits. Therefore, they deliberately employ single ended, non-symmetrical topology. And for the push-pull output stages they deliberately don't employ supposedly symmetric PNP and NPN devices, instead relying entirely on NPN devices (which, by the way, are superior to PNP devices in speed and in other important ways).
Once the Plinius engineers made this decision to deliberately not employ symmetrical circuitry, the next step in their thinking became crucial and obvious--and ties in perfectly with their aforementioned conceptual realization that musical naturalness demands a transfer characteristic having a natural decline of progressive orders. You see, if a circuit is deliberately made asymmetrical, then its transfer characteristic naturally tends to be asymmetrical, and it is the even order byproducts that are asymmetrical. So it is a piece of cake to get a proper proportion of even order byproducts from an asymmetrical circuit, in order to mix in with the odd order byproducts, to obtain the desired overall amplifier transfer characteristic with a musically natural declining progression, a progression similar to that you hear with live music. And the design of a single ended asymmetrical circuit can be deliberately engineered to give a specific transfer characteristic, with a specific progressive decline of progressively ordered byproducts, including both even and odd ordered byproducts. Thus, the Plinius engineers could tweak the design of their asymmetric circuit to yield a transfer characteristic having a composition with precisely that progressive decline which sounds most musically natural, which best emulates the progressive decline we hear with live music. In particular, they could engineer the transfer characteristic to have a composition that is predominantly 2nd order, with somewhat less 3rd order, and then progressively smaller amounts of progressively higher orders. Working with single ended asymmetrical circuits, they could even design the 3rd order (and other odd orders) to be compressive rather than expansive, thereby giving their solid state circuit a musically natural softness (similar to what happens to live music heard at a distance), rather than the artificial hardness that the expansive odd order distortion of other solid state designs adds to music.
After the Plinius engineers had achieved the naturally declining progression for the circuit's transfer characteristic, they could still then employ means to reduce total overall distortion to miniscule levels, while still retaining that desirable naturally declining composition for that miniscule residual distortion. Thus, the Plinius electronics have miniscule distortion levels that are comparable to other solid state products (the Odeon's THD, even at full power, measures less than .05 percent). But the composition of the Plinius' miniscule distortion, the composition of its transfer characteristic that gives a Plinius amplifier its naturally musical sonic personality, is very different from (and much better than) the composition of the miniscule distortion in most other solid state products, the composition of their transfer characteristic that gives them their artificial sounding sonic personalities, even at ordinary listening levels. Incidentally, the circuit of a tube amplifier (especially a triode amplifier) intrinsically can also have a natural progression for its transfer characteristic, which is why these amplifiers can sound so musically natural as well (and why the Plinius solid state products sound so similar to good tube electronics).
Note that this musically natural progression includes the even orders as full (indeed naturally dominant) members, in contrast to most other solid state designs that virtually eliminate even order byproducts, leaving an artificial sounding transfer characteristic consisting of only odd orders. Note also that this progression emphasizes the lower orders over the higher orders, in contrast to most other solid state designs in which high feedback creates a predominance of artificial sounding high order byproducts.
The Plinius engineers surely tweaked their circuit design until its transfer characteristic had the composition that sounded the most musically natural, the most like their experience of live music in a concert hall, heard of course from a distance, just as you would hear it (note that emulating live music heard up close would require a subtly different amplifier transfer characteristic, mimicking less air distance nonlinearity, but more ear mechanism nonlinearity due to the higher SPL). Thus, it is no accident that the Plinius sound emulates so well the sound of live music as you know it from your concert hall audience seat, even when playing recordings that are typically miked much too close up. It has been suggested that even order harmonics (especially lower order ones) help the rich warmth that you hear from live music heard from a distance. The Plinius sound gives that same rich bloom to music's warmth region, probably because the Plinius circuits were tweaked to emulate live music, and thus retain in their transfer characteristic a rich proportion of lower even order harmonic byproducts (in diametric opposition to most other solid state circuits, which starve out all the even order byproducts completely, leaving the music artificially bleached and lean). Likewise, the Plinius sound's polite upper midrange and the sweet softness in the trebles, which also emulate so well what you hear from live music in the concert hall, were no doubt achieved by tweaking the parameters of the circuit so that its transfer characteristic would have a musically natural sound to its composition.
And that, dear friends, is how Plinius is able to give you the rugged practicality of solid state combined with the natural musical sound you can hear from tubes and from live music itself.
Perfectionist Features In A Home Theatre/Surround Music Amplifier
The virtues of the Plinius sound have already been well established for a number of years, in Plinius' lineup of stereo power amplifiers, line sections, phono preamplifiers, and integrated amplifiers, all two channel units intended for music systems. The highest end power amplifiers in today's Plinius lineup include the mighty SA-250, a monster (156 pounds) 200-watt-per-channel class A stereo amplifier, and the more recent SA-102, which, although rated at only 100-watts per channel class A, incorporates Plinius' latest design refinements, and therefore reputedly offers even better sonics (more refined upper frequencies) within its power capability than the older SA-250. These two premium power amplifiers exemplify the Plinius sound at its best.
Now, the challenge for Plinius, as it is for every manufacturer developing a premium quality home theatre power amplifier from their best stereo power amplifiers, is to try to shoehorn five or six channels into the same general type of single chassis that in their stereo amplifier only had to support two channels, while sacrificing as little as possible of the premium sonics that make the two channel model sound so great, all within constraints of reasonable package size, weight, and cost. And thus, the key question for us to ask at this point is, how well does the Odeon, the multichannel home theatre package, deliver the best possible approximation to the Plinius sound heard so impressively from Plinius' best two channel amplifiers?
The answer is that the Odeon can do very well sonically in delivering the Plinius sound to high-end surround music and home theatre systems. Plinius has succeeded very well in achieving their design goal, delivering the sonics of their premium stereo music amplifiers to a surround music system (where premium, musically natural sound is, of course, crucial), as well as to home theatre systems for mature film connoisseurs, who also want natural reproduction of soundtrack music, voice, and atmospheric effects. Thanks to Plinius' intelligent engineering, the Odeon is as close to a no compromise home theatre power amplifier as you can get.
You can tell that the Odeon is a no compromise home theatre effort even before you listen to its sound. The impressive bulk of this amplifier (23 inches deep x 18 inches wide x 10 inches high), housed in a handsomely sculpted case, already tells you that the Odeon means serious business. Its 120 pound weight, about as heavy as they could make it without breaking your back, testifies to the massiveness of the innards that are needed to make a great sounding power amplifier (two crucial keys to mighty sound, the power supply and the output stage heat sinks, are both heavy, so the weight of a power amplifier tells you that the manufacturer has not skimped on these key factors). The Odeon is not inexpensive, which again tells you that the manufacturer has not skimped on the insides. Even the specs tell you that the Odeon is a heavyweight assault on premium home theatre sound. The rated power of 200 watts per channel matches that of Plinius' most powerful two-channel amplifier, the SA-250. Note that the Odeon puts six of these 200-watt channels on one chassis, and gives you these six channels of Plinius sound at a relative bargain price ($10,995, far less than three SA-250's would cost you at $9,995 apiece).
The Odeon also boasts no-compromise perfectionist features that are not so obvious to the casual observer. The humongous power supply, available to any and all channels as the signal demands warrant, has its huge capacitor filter bank supplemented by local filter reservoir caps within each channel module. These local supplementary caps do provide additional reservoir storage, but their most important function is in the service of perfectionist sonics. They provide a fast, nearby, low impedance source of energy for each module, so that music's fast transient demands can be met quickly and accurately. And they also provide benefits in dynamic crosstalk isolation among channels, which can improve stereo imaging, improve the quiet blackness of background noise and haze (thus improving intertransient silence), and even lower cross modulation distortions.
Another hidden perfectionist feature concerns grounding. Grounding paths are crucial in every piece of electronics, because the ground provides the reference baseline that literally defines the music signal in the circuit. If a poor grounding path in an amplifier provides a sloppy reference baseline, then the music signal itself will be sloppy and inaccurate in that amplifier, since the music signal is defined by that baseline. In perfectionist high-end stereo electronics, it is recognized that star grounding through one single point (and other similar techniques) give superior sonic results. But such perfectionism is usually abandoned for home theatre amplifiers, where instead all channel modules might well be grounded on several sides through many points, often via the metal cage's mechanical guide rails that conveniently allow module substitution. This can create a messy ground path, which can compromise sonics in other home theatre amplifiers. But not in the Odeon. In the Odeon, the perfectionism of pure single point ground paths is maintained, for each and every module. The ground reference for each amplifying module is supplied via a dedicated single wire, not via the metal cage. This means that, if a technician wants to substitute modules, he must take the trouble to desolder and resolder this wire. But this is a minor inconvenience, compared to the sonic benefits you receive from this perfectionist design integrity.
Yet another hidden perfectionist feature concerns the power supply. You can see the massive capacitor filter bank energy reservoir when you open the top lid, but you can't see the power transformers hidden underneath. That's a plural, not a typo. Instead of the usual single power transformer, the Odeon boasts four premium toroidal power transformers, all connected in parallel. Why four instead of one? Plinius put six modules in this amplifier, each capable of delivering 200 watts. That's a lot of power. But 200 watts times six indicates just the potential total power delivery of this home theatre amplifier. These modules couldn't actually deliver all this power simultaneously unless they could get all this energy simultaneously from the power supply. So the power supply has to be massive. In particular, it has to be able to deliver high current, throughout the musical spectrum, to all channels. Plinius measured the actual transient current requirements while playing real music samples loudly through real loudspeakers, and they found many transient peak current demands up around 30 amps, which is very high. So they designed the Odeon modules to be able to furnish 40 amp bursts from each channel, and they then also had to put this amount of muscle times six into the power supply (the Plinius stereo amplifiers feature similar high current capabilities).
It's worth noting that the Odeon design shares this massive energy resource among all channels in parallel, which gives the further advantage that all the power supply energy, sufficient for all six channels simultaneously, is available to just one channel (or just some channels) if there is a loud transient (say a thunderous sound effect) in just one channel (or in just some channels). The Odeon's massive capacitor filter bank provides an intermediate short term reservoir of current energy, but the ultimate energy source is of course your powerline (more about this below). And the high current refill from your powerline into the capacitor filter bank must come through the power transformer. So obviously a massive power transformer is called for, with very high current capability. Most other home theatre amplifiers employ only a single massive power transformer. But the Plinius engineers cleverly use a more perfectionist approach, by giving you four power transformers instead of just one. This has several advantages.
First is a question of real estate. The Odeon's footprint on your floor is already huge (its 23 inch depth is already much too deep for any conventional shelving unit), and the rear portion of the amplifier is occupied by the plug in channel modules, which leaves only the front of the amplifier for the massive power supply. Plinius virtually fills this area with power supply filter caps, in order to give you a perfectionist level of energy storage in the cap reservoir. Which leaves no real estate for the power transformer (unless they were to make the Odeon's footprint even larger and deeper). So they put the power transformer underneath the filter caps. But a single toroidal transformer of adequate current capability would be too tall. By employing four squat toroidal transformers instead of a single tall one, they can give you the high current capability without making the already huge footprint of the Odeon even bigger.
The second advantage of using four power transformers connected in parallel, instead of just a single power transformer, concerns power supply impedance. Every power supply has some series impedance when acting in its role as an energy source. This source impedance starves or chokes off a full flow of energy to the signal processing circuitry (the amplifying modules), and also to the output terminals, for which all the signal amplifying circuitry merely acts as a valve or gate (more on this below). For any amplifier to deliver full power, especially full current, as demanded by the audio signal, the power supply source impedance should be as low as possible. By connecting four transformers in parallel in the Odeon, the Plinius engineers cut the source impedance to one quarter of what it would be from one of these transformers alone (and lower than it would have been from using a single larger transformer). Of course it's expensive to employ four power transformers instead of one. Plinius could have saved themselves (and you) money by employing only one power transformer, as most other home theatre amplifiers do. But that's the price to pay for perfectionist design in a home theatre amplifier.
The third advantage of using four power transformers instead of one concerns spectral bandwidth. Most large, expensive power supplies, which try for low source impedance, still run into trouble at the upper frequencies of the music spectrum. Their source impedance rises at higher frequencies, which starves current delivery for musical attack transients (most of which contain abundant high frequency energy demands within their sharp, high current peaks). This also problematically gives an amplifier non-uniform sonic performance over the range of the musical spectrum, since high frequency transient demands are starved from getting adequate current (which is one reason why so many amplifiers sound great for lower frequencies but then run into sonic problems at upper frequencies, especially when the music transient demands get loud and complex).
Transformer design is a complex matter of engineering tradeoffs, and smaller transformers can often be designed with better high frequency performance than large transformers. Thus, by employing a large but not humongous toroidal transformer design in the Odeon, Plinius is able to use transformers that have better high frequency performance (maintaining a low source impedance out to higher frequencies). They can thereby give you better current delivery for music's higher frequency transient demands, which also maintains a more uniform low source impedance for the entire spectrum, thus maintaining more uniform sonic performance for the whole musical spectrum. And then, by employing four of these smaller transformers in parallel, Plinius can provide the Odeon with ample total current flow capability, giving you ample reserves of energy, and uniformly so for the whole musical spectrum.
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