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Advanced Design Features of the AMR-77 Series
The original Philips TDA1541A digital-to-analogue converter
There are many poignant examples of the exceptional design and engineering that has made the Philips DA1541A the "golden era" chipset for compact disk, such as its use in the legendary Marantz CD-12/DA-12 CD Replay system which is still used as personal reference by noted reviewer Ken Kessler.

The Philips TDA1541A uses external digital and analogue filters, allowing the designer the freedom to choose the optimum solution for digital and analogue filtering. This is in direct contrast to subsequent and even the latest generation of DAC chipsets, where the digital and analogue filters are located inside the chipset where it cannot be changed or improved.

In addition, onboard circuits will normally make heavy comprises due to the size constraints of the silicon die and inevitably generate higher noise and jitter levels due to the close proximity of the internal circuits.

Furthermore, the Philips TDA1541A's unique dynamic element matching offers exceptional performance and together with the fact that many of its parts are external to the chip or accessible externally, enable the competent designer to maximise each and every facet of this DAC's truly exceptional performance.

OptiSignal® conditioning circuit
The CD-77 is at the envelope of the "Redbook" standard for compact disk audio reproduction due to extensive and exhaustive research and development by AMR into maximizing the sonic performance of the Philips TDA1541A.

AMR's research and development team's prior experience with the Philips TDA1541A in other compact disk players as well as with designs of their own, intimated that the full performance of this chipset had yet to be extracted.

As a result, a considerable amount of time and resources was therefore devoted into understanding the silicon die of the Philips TDA1541A. The result is the OptiSignal®; conditioning circuit which has been designed to optimise every single operating parameter of the Philips TDA1541A including off as well as onboard circuits. The resulting sonic performance has been extended close to the theoretical limit.

AMR is confident that the CD-77 compared to other compact disk sources past and present (even those that similarly employ the Philips TDA1541A), is able not only to compete, but excel and re-define a new standard in the ability of the Redbook compact disk medium to bring music to life. Put simply, the CD-77 has recovered much of the ground lost by compact disk to well-implemented vinyl front-end systems.

OptiSample® digital engine

Earlier, it was explained that the digital and analogue filters of the Philips TDA1541A are externally placed. This has allowed AMR to uniquely combine the best of the classic with the latest, through the incorporation of the most advanced Digital Signal Processing (DSP) engine from Texas Instruments to perform the function of the digital filter.

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OptiClockLock® system

Conventional compact disk players use several generic clock crystals (such as one for each of the DAC, transport and micro controller). Looking more upmarket, even so called "super-clocks" are of a mediocre commercial grade that is not that much better than generic clocks when it comes to low jitter performance.

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OptiReg® digital power supply

As a rule, digital circuits require extensive regulation to reduce digital noise and phase noise, which if left unresolved, pollute the audio signal. They are also needed to meet the tight supply voltage tolerances required for optimum operation of digital circuits.

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OptiDrive® transport mechanism

Back in 2001, Philips Electronics ceased production of its own 'industrial standard' compact disk transports. Presently, new so-called "Philips transports" are quintessentially Asian-made clones constructed to much lesser standards and are of questionable reliability.

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OptiValve® analogue output stage
Typically, so-called valve equipped compact disk players only use thermionic electron valves as an add-on in the final buffer stage. For most, the preceding analogue stages use generic solid-state operational amplifiers (Op-Amps) drawn from textbook circuit designs. The valve sections often appear tacked on at the end seemingly as an afterthought as in "shouldn't there be some valves in this?"
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OptiBus® USB digital input
With the implementation of the OptiBus®USB digital input, all music content (including WAV, AAC, WMA, MP3 etc.) stored on the ever more ubiquitous personal computer can finally be played back through the CD-77 in their full glory. In addition, with the ever increasing storage capacity of the personal computer, it is now possible to turn a personal computer into an audiophile jukebox with storage capacity of hundred of CDs without any loss of sound quality.

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OptiGain® circuit
OptiGain®is AMR's amplification circuit of the audio signal to a desired level in the most optimal way. In order to interface signals, often some form of gain is needed. Audio equipment requires both voltage gain and power buffering - voltage gain, where levels need to be increased and power buffering where loads (like speakers) need to be driven.

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OptiLevel® direct volume control system

OptiLevel®is a patent-pending "direct path" precision volume control system. Conventional potentiometers use either carbon or conductive plastic tracks riveted to metal tags or pins with a "wiper" scraping over this track and a second contact. This arrangement significantly degrades the music signal.

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OptiOperation® modes
The AM-77 has not only exceptional form but also incomparable functionality. The operating sensitivity and impedance of mainstream speakers vary widely (typically from 80dB to 95dB and 4 ohm to 16 ohm). Add to this the popularity of bi- or even tri-amplification for suitably-equipped speakers, AMR has appreciated that there is no single system configuration that suits all or even most needs.

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OptiProtect® circuits
Throughout the AM-77, AMR has subtly and carefully integrated electrical safeguards to cater comprehensively for potential direct current, over-voltage, under-voltage, overload and over temperature situations. The only stipulation was that the integration of the protection devices had to be benign so as to result in no sonic degradation whatsoever while protection circuits are not engaged.

OptiCool® zero heat sink design
In testing heat sinks, while admirable in a cooling capacity, unwanted vibration and resonance was discovered to the point that it audibly impinged upon the sonic performance of the AM-77. This should be no surprise given that the traditional heatsinks is effectively a combination of many tuning forks. AMR resolved this issue through the "zero heat sink design" which as its name suggests, did away with conventional heat sinks but still managed to effect exceptional cooling performance without unwanted vibration and resonance.

OptiPower® supply
Any Audio Amplifier is only as good as its power supply. This old truism has been said often, but is actually true. An amplifier circuit of any kind does NOT really amplify the signal in the strictest sense of the word. Rather, it acts as a signal-controlled valve that lets more or less of the power supply current flow into the following device (hence the original English name of thermionic electron valve for the first "amplifying" device).

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OptiMains® power conditioning
In contrast to the "classic era" methods employed in the manufacture of its transformers, AMR is proud of its patent-pending and groundbreaking OptiMains®power conditioning circuit which is at the envelope of audio mains design. The specially designed intelligent electrical mains control circuit is comprised of several key technologies that combined, immunise the power supply in AMR equipment from just about all noise problems associated with modern mains systems.

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OptiTrans® hand-made, proprietary design transformers
The power transformer of the audio equipment is usually the most compromised due to its being the single most expensive component. Due to this fact, the downstream power supply and audio chain (remember, an amplifier is actually a valve to let more or less current flow from the power supply into the load) is ultimately compromised unless it has the highest quality mains transformer section at the outset.

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OptiSeal® Power Supply Circuit
Not all power supplies are the same. Often a minimum number of windings and transformers are employed to provide a minimal number of rectified voltages, which are then distributed throughout the device and regulated where needed, using a bunch of 10 pence each regulator chips.

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OptiChassis® design
Beyond the gorgeous extruded and machined outer aluminium chassis, less obvious key design variables resulted in sonic as well as aesthetic gains.

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OptiIsolate® supports
One of AMR's core philosophies is to ensure that its components have no single "weak link". For a long time many audio enthusiasts have been aware of the effects on the sound by the various supports equipment is placed upon, what kind of "feet" are used under equipment and so on and so forth. In fact, a significant subculture has sprung up around this. The aim was to isolate AMR equipment maximally from the resonances in the supporting stand or shelf, while keeping the principles of simplicity and utility in mind.

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Hand-selected, premium electronic components
With AMR components, unusually, the closer examination, the more significant is the appreciation of the degree of commitment to the product and the level of attention to the smallest details. Not only is there an exceptionally high quality of the fundamental design and of general implementation, but also the quality of components has been given the same, undivided attention.

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