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Classic Audio's Design Philosophy

Returning to the objectivity of the 20th century

Glancing around at the marketing and review literature surrounding the vast majority of HiFi products on the market today, it may seem that it has always been the case that such items have been advertised by manufacturers and promoted by reviewers based upon highly flawed subjective testing. This trend has only appeared, and reach its current state of dominance, since the 1980s. Before this, consumers would choose products based upon their noise, distortion and frequency response characteristics, in addition to any other product specific parameters, and manufacturers would be in close and fierce competition to deliver the very best technical performance at the right price.

Technics SA200 Receiver

A 1979 receiver proudly proclaims a low THD among its contemporaries

Although some subjective review was given around this time, it was mainly provided as a supplement to the consumer, supporting that a measurable characteristic did indeed yield a palpable result (for example a loudspeaker with an independently verified flat frequency response would be described as 'delightfully uncoloured'). Subjective review alone in the modern fashion was unheard of and every year, spurred on by the markets demand for better specs, the objective performance of consumer audio equipment improved.

By the mid-1980s, that the CD - and with it digital audio - had been accepted as the way to go as far as high quality reproduction of sound went, especially in regards to classical music which required a dynamic range that vinyl records had more often than not failed to accommodate. This caused an inevitable shift away from the from products such as high end turntables, cartridges and various forms of apparel; towards a few very large manufacturers who had the advantage of a then proprietary technology and a very strong economy of scale on their side. Smaller manufacturers of turntable related equipment, along with once revered dispensers of advice regarding such equipment, came to realise that they were very much out in the cold when it came to continued demand for their products and services; they were desperate to convince the HiFi aficionado that they were still needed.

It was of course pointless to make an argument based on the measurable performance of these two forms of music consumption, so in order to work around the troublesome reality of their predicament, the promoters of these swiftly wilting products changed tactics and started to make claims that there were many things missing from the dry analysis of the day. As luck would have it, there were several other smaller parties who had managed to get their feet quite firmly into the door to promote inferior amplifiers and pre-amplifiers that they themselves had made of their own accord, referring to their over-simplified design as a virtue, as opposed to the Achilles heel that it really was. In addition to this, there were downright charlatans selling products which were impossible to manufacture without the full knowledge that they were quite useless, who saw an ever increasing opportunity to go mainstream.

Soon these groups were publishing articles that disseminated their quite heroically flawed new philosophy in reputable HiFi and electronics magazines. Those who had no knowledge of electronics, acoustics or any matter relating to audio engineering began to consider themselves to be ‘golden eared’, making various claims that they could hear differences between components, cabling, even the colour of CDs, that could not be measured by conventional means or even supported with sensible explanation. None of these listening tests were conducted using the sort of blind and double blind techniques required to weed out the biases needed for any successful psychological study; the preferred equipment was always in view of the listener and has always been every since.

The unsettling trend continued, and before long objectivity had faded into the background; replaced by colourful marketing language. The emperor had put on his new clothes, of such fine threads that only those with the most discriminating of senses could truly appreciate their majesty. Everyone who questioned the new status quo was told that they simply had not the refined perception that the perpetrators of the situation had. Experimenter expectancy biases combined with dishonest sales tactics quickly gave the impression that there was indeed some form of benefit to be had with all grades of snake oil, from bizarre cable lifters to special power conditioners that really did nothing but generate profit for the very shady individuals that made them.

Newcomers were quickly bombarded with the prevailing nonsense, and being in possession of no other source of information, accepted it without question, investing their money in products such as ‘audiophile power cables’ that yielded absolutely no audible benefits whatsoever. Many of those who had very good systems indeed quickly became infected with a sense of paranoia that perhaps they were suffering from some undefinable ills in ‘power quality’, ‘cable transparency’, and all manner of technical sounding explanations that in reality had as much credo as claims to the effect that flapping ones hands will generate enough lift for flight.

The current state of affairs at the present is much the same, and although some companies are moving in the right direction, they are outweighed by the many who are not. Classic Audio Ltd is strongly focussed returning to the objective and quantifiable approach to HiFi that produced some of the very best and now highly sought after units of the late 1970s and early 1980s. Many manufacturers try to throw the potential buyer off the scent of getting down to the real brass tacks with vague and whimsical references to 'sonic clarity', and the all time favourite 'musicality'; here no time is wasted in bombarding the customer with weasel words, flowery language, or technical sounding meaninglessness. Due to the strong degree of design competency required to effect an excellent specification, great pride is taken in showing an excellent specification straight off the bat without hiding it behind a wall of new age nonsense!

HiFi means high fidelity

HiFi is a word that is bandied about with seemingly gross abandon today with little regard to what it actually means. Most people associate HiFi with 'good sound' although what exactly makes the sound 'good' is a mystery to most people. Usually it means something on the order of sizzling treble and booming bass that can go nice and loud without too much in the way of audible distortion, although the latter is sometimes quite debatable. Most manufacturers, especially those who make loudspeakers, are well aware that a flat frequency response can sound 'dull' to prospective buyers in comparison to one that rises at both ends when they are auditioned side by side.

Poor frequency response

An expensive loudspeakers frequency response that might sound exciting, but is definitely not high fidelity

As a result of this phenomenon, and also due to the move away from objective measurement towards the easy - and unfortunately more relatable - subjective review, many manufacturers have been designing and selling electronics and loudspeakers fall far short of the mark. As can be seen in the above image, it seems that trifling matters such as frequency response, which should be as flat as possible, are being thoroughly neglected. It is unlikely that the consumer will have the opportunity to assess theses parameters properly before making an informed decision and a shop floor is certainly not the best place in the world to conduct already highly fallible listening tests, particularly if a salesperson is present.

Many phono pre-amplifiers in particular suffer very greatly here as overly simplistic circuit topologies that benefit the designers ease of implementation, in contrast to the performance that the buyer receives; result in a very unsatisfactory return on investment. Poor RIAA accuracy from inappropriate component choices that colours the sound, sometimes to the liking of the reviewer; excessive noise from choosing the wrong kind of input amplifier noise characteristics, which is usually then advertised as the latest-and-greatest; easy to design passive RIAA equalisation networks, that fatally limit headroom margins and guarantee excessive distortion and overload artefacts that will greatly increase the intrusiveness of what would otherwise be tolerable clicks and pops. Many of these things are a matter of personal preference for some listeners who like ‘grit’, ‘punch’, and ’sparkle’, but they are certainly not bringing the listener any closer to the original source. All of the above are present to an alarming degree in a great deal of phono pre-amplifiers on sale at any moment, and worst of all these horrors are made into selling points by the marketing teams that do all of the real heavy lifting.

Classic Audio Ltd does not seek to produce pre-amplifiers that ‘sound good’, only to sound as accurate as possible. This is done by ensuring that frequency response is kept as flat as possible within the range of human hearing, as little noise and distortion as possible are added to the audio signal, and finally that a plentiful reserve of headroom is available to ensure that grating clipping does not have a chance of occurring in normal use. HiFi means ‘high fidelity’, which means accurate reproduction of sound in a quantifiable and repeatable manner, and that is exactly what Classic Audio products are designed to deliver, and deliver in practice.

A scientific approach to high fidelity

Despite the claims of various parties of questionable interest, high fidelity audio design is not a ‘black art’ that can only be practiced in the evanescent cauldron of trial and error by the most elusive of wizards. There are no fickle winds of fortune – requiring the blessing of mystical sages - that blow in the most unpredictable of directions, that simply cannot be explained by any practical means other than the most vague of allusions. In essence, high fidelity audio is the offspring of two well-known sciences; psychoacoustics and electronic design.

The field of psychoacoustics is very well studied and in stark contrast to what is often overheard in the conversation of many enthusiasts of the subjective mind set, we are very much aware of what we can and cannot hear when it comes to all of the parameters in question. In relation to high fidelity audio, all of the questions were answered over 60 years ago. Claims to the contrary should not be met with the sensible argument that the purveyor of said claims should publish a study to prove them against the massive body of evidence in possession of the discipline of psychoacoustics. Unfortunately, for some reason unbeknown to the author, they are never successful in turning the status quo upside down with such theories of relativity overnight!

Once we know what is required to reproduce sound transparently to the human ear, it is a straightforward – but often not simple – task of designing circuitry that meets these criteria. Great care is taken to understand the less than ideal attributes of the components that we have at our disposal today and to marry them in such a manner as to mitigate flaws such as non-linearity with its alias distortion to the point where they are far below what we know the limits of our perception are.

Classic Audio Ltd is strongly focussed on designing its analogue circuitry to the highest standard of performance against what can be shown to be the characteristics of our perception of sound. A firm understanding of the characteristics of the components used, based on measurement and calculation, is put into practice in all Classic Audio products. No stone is left unturned and every part of the circuitry is optimised before being measured to confirm it is doing the very best that it can. By doing this, it is ensured that whenever compromises have to be made – which is always the case for analogue circuitry – a happy alignment is cast that should satisfy all the necessary requirements before all of the insignificant ones; yielding truly outstanding results in contrast with competition who might prefer the rather mediocre ones produced by wishful thinking.

Performance from topology, not magic components

Most of the time you never hear the end of what new, special, or somehow magical components have been put into an audio product to make it stand out from the competition, whether it be the latest op-amps, designed for use in submarine sonar systems - at a cost of 10+ times that of the professional audio industry-standard NE5532, or some sort of specially fabricated hand-made capacitors, cryogenically treated resistors, or silver wiring. These expensive and unnecessary additions, particularly the latter ones, do almost nothing to improve the actual performance of a piece of audio equipment, and in many cases actually cause measurable deterioration as they are shoehorned into a design without any consideration for whether or not they will do any good, in favour of simply being able to boast of their inclusion to potential customers. A lot of the time, the expensive op-amps that are chosen over the quite excellent NE5532 and NE5534 types - designed especially for high quality audio design and made inexpensive through an economy of scale brought about by their ubiquitous and well-informed adoption in professional audio - will be far less stable, noisier, and generate more distortion when put to the test in-situ.

What matters most, is not the actual components used, but the circuit topology used; how they are arranged together. This is where the high performance of any high quality design is truly crafted, once some basic requirements such as suitable op-amp characteristics, and good component tolerances have been chosen. The arrangement is just as important, if not more so, than the instruments themselves.

Volume control topologies

Two similar optimised volume control topologies with very different noise performance

The image above is an excellent example of the adage of the last paragraph in practice to hammer the point home with. They are both inverting volume control circuits of the kind that would be found in a position penultimate to the line outputs of many conventional line pre-amplifiers. Volume controls A and B appear very similar, both with identical potentiometers, op-amps, and maximum gain of 8 (18dB) with all component values optimised for the best possible performance in each topology. Volume control A is a very conventional circuit that has seen use in many commercial and DIY pre-amplifiers, while volume control B is a negative feedback active topology original to Classic Audio. With the control position set to allow the audio signal through, so that its amplitude is exactly the same going out as it is going in (unity gain), volume control A adds 3 times as much noise (-103dBV vs -113dBV) to the audio signal as volume control B, which further deteriorates to 10 times as much (-103dBV vs -123dBV) as the control approaches its minimum setting.

When connected to an amplifier and speakers, or active speakers, a slight but annoying hiss can be heard in proximity to the loudspeakers, while volume control B is whisper quiet. Even if an ideal, and therefore non-existent, op-amp with absolutely no noise at all is used, volume control A only gains a 30% (3dB) improvement. Using an expensive esoteric op-amp, in the style of certain competitors, may only yield a 20% (2dB) improvement at the very best, which still leaves it a good 8dB, or over 2.5 times as short as volume control B. Furthermore, Classic Audio's volume control B requires a lower value and less costly coupling capacitor (C3) of only a tenth of the value of that of volume control A (C1); a saving which can be passed onto the customer.

Best of all, once designed, a good topology costs absolutely nothing more to manufacture once designed; often even less as above, which allows Classic Audio to offer its customers superb value for money. All of Classic Audio's products are designed with this philosophy in mind which yields competition beating performance with what might seem to be very common-or-garden components indeed. That is not to say that high quality components are not used, they most certainly are with 1% metal film resistors, matched distortion free polypropylene equalisation capacitors, and Panasonic FM series aluminium capacitors; widely considered the very best made. However, extortionately priced parts that seem impressive on the datasheet, but in reality are unable to match the benefit of proper topology, are most thoroughly avoided.

Sold on real world performance

Classic Audio strongly believes in designing, measuring, and testing its products in accordance with the real-world situations in which they will be used. This means, however tempting it might be, refraining from publishing misleading figures regarding the performance of products. These include, but are not limited to; measuring frequency response wide-band with low cut-offs, to hide in-band variations that would be off-putting; only measuring distortion at low levels and not full scale, to mask things like capacitor non-linearities; or only publishing 'A-weighted' results in absence of unweighted ones, to muddy the waters and hide various gremlins at the lower end of the frequency spectrum. The list goes on and on, and there seem to be a limitless set of dirty tricks that unscrupulous companies can use against the consumer in this field.

Hiding input current noise by shorting inputs

This units specification is defined with the inputs shorted, hiding its input current noise

The image above, lamentably from one of the better companies, is a crystal clear demonstration of this unfortunate proclivity in action. The noise performance is only shown 'a-weighted' which is not very useful at all, and even worse with the inputs shorted. The author has knowledge that this unit uses an input amplifier IC that is completely unsuitable for moving magnet inputs, and not too great for moving coil ones either; a most depressing compromise. Notice that the input is shorted to hide the fact that the relatively high input current noise of this IC, which would otherwise severely degrade the noise performance when connected across a high impedance moving magnet cartridge.

Classic Audio's published specifications are all measured with real world loads on their inputs and outputs, with multiple or continuous measurement points to show that no cherry-picking has taken place whatsoever. No 'sampling', which essentially translates into picking the best performing unit made to represent the specification, is used. Customers can be certain that they'll be realising the advertised performance when they include Classic Audio products into their systems.

No secrets

None of the circuitry used in Classic Audio's products is shrouded in secrecy and confusing terminology. Most of the topologies used in Classic Audio products are, or will be, described in great detail in the articles section of this website; Classic Audio is happy to reveal and explain the careful design choices involved in the kind of circuitry that can be found in its products, for the purposes of education and - of course - self promotion.

The link above will take the reader to an ever-growing list of technical articles published on the Classic Audio site for educational, and - depending on ease of amusement - entertainment purposes. All the technical articles are written from a dry practical perspective, firmly rooted in provable real world results. There are no 'proprietary techniques' that are only vaguely alluded to and seem yield very uninspiring specifications, or preposterously patented re-hashes of tried-and-tossed-aside techniques for the implementation of RIAA equalisation, to name a few items floating on top of the pond at the moment. Classic Audio believes in describing its products with an equal level of transparency to that which they are able to deliver sonically. No bones will be made about explaining and describing the superior operation and design of its products with customers, and relishes the opportunity to discuss the gory details with anyone in possession of the stomach for them. There's no such thing as too much information here!

Product Quality

Built to specification, not cost

When most audio products are reviewed and marketed, there is usually some mention made to a product being within a pre-ordained price range, rather than a set of performance characteristics defined from the start. Classic Audio products are not designed and built in this manner; the objectives are set and once they are met, the price is then decided. This ensures that no compromises are made, to be hidden away in the fine detail as they often are for most other products and ensures that the customer receives exactly what they want, without any gnawing disappointments after the fact.

Built to last, and be repaired

So many things seem to be made to be thrown away, with the implication being that they will be replaced by fashion or obsolescence before they themselves fail. Analogue audio is very much a mature and stable technology, and as such should be built to last as long as possible. In order to accomplish this, Classic Audio only uses parts that are rated for tens of thousands of hours, such as the Panasonic FM series electrolytic capacitors used; by far the most mortal of components in audio electronics. High quality nickel plated connectors are used instead of the gold plated variety that just look awful once the economically mandated thin layer of gold wears off after a few connection cycles. Linear transformer based power supplies which, while contributing lower interference, have a practically unlimited longevity are included with all units sold to make certain that Classic Audio's products will never need to be discarded. High quality metal switches, rugged panel mounted headphone connectors, all through-hole technology, the list goes on-and-on...

Should a unit fail for any reason, the parts used are all readily available from all the major electronic component suppliers, and also can be foreseen to be available for a long time into the future. All IC op-amps are mounted in high quality turned DIP sockets, meaning that should one of these little devices receive a fatal blow from any murderously inclined piece of equipment it has been connected to, a repair can be easily effected without the need to even pick up a soldering iron.

Classic Audio products are designed and built to give more than a lifetime of reliable service if treated well, hopefully being passed down for generations to come. They are not designed to appeal to the whims of fashion, and instead take the route of a timeless, classic quality that can always be appreciated.

Carefully assembled in Kent

All Classic Audio products are hand assembled from component level with care in a state-of-the-art residential spare room facility by company owner Michael Fidler. This only allows for limited small-scale runs but makes certain that product quality is exactly as intended by the designer.