Apr 102013

A few words before the review.

I am well aware this review is quite late – it should have been completed and published Dec 2012 and is also now out of sequence so to speak with the Wireworld USB cable reviews and the iFi Audio iDAC and iUSB Power reviews which should have followed it but I hope I am forgiven as a personal loss meant I shelved most of the reviewing I was doing around November last year and as such the AMR DP777 review was shelved – though I was about half way through doing it – until recently when I finished it off.

I will warn you before hand that this is probably the longest review I have written but the subject required it and so it is what it is part product review, part getting to grips with technology and part personal travelogue as attitudes changed and a mind opened. One thing this review has taught/reminded me, is it is wise to never say never as these can be famous last words.

I hope you enjoy it.


Those who know me well, know of my fondness for AMR both as a company and their products – I own a CD77 – and I have also known and respected Vincent Luke of AMR for quite a few years since I met him during one of the Heathrow Park Inn shows when Real HiFi were the UK distributors of AMR, so any opportunity to hear and review a new – well relatively new – product fills me with great excitement and in this case a little trepidation. How so you might ask?

Well because this particular review will by necessity take me somewhere I have no real desire to go either personally or professionally and that is into the world of computer audio. The cold hard facts are I am an analogue kind of guy in my thinking and in my day to day life, I have not embraced the virtual digital world to any great extent – in fact one could say I hold it at arms length much as one might hold a snake and I don’t really intend to do digital virtual re reading or listening to music until I have no choice. The world of downloaded books and music to me at least smacks of the Emperors new clothes in that you part with cold hard cash – in this day and age of austerity and increasing unemployment that cash is increasingly hard to come by – and many use it to buy nothing tangible, nothing physical, which to my mind is crazy.

In the good old analogue days one bought a paper book or music stored on a physical format and one had a real world relationship with it. You could hold it, feel it, smell it and one had to actively physically use it- oh yes and you actually owned it. One read one book at a time and one listened to an album – remember vinyl – the whole way through, not as a series of sound bites. To my way of thinking doing anything else leads to a shallower relationship with books and music, one in which the quality and art is lost to a base line commodity but there is sadly in fact no actual commodity as one – or so it has been revealed recently – only rent the books or music you download. These items you buy don’t belong to you, you can’t pass them on, lend them, and at any time – of their choosing – the company who supplied them might revoke your licence to read or listen. Truly to me we are seeing the greatest marketing con of the century getting people to pay for nothing.

However regardless of my thoughts and incredulity on this matter – I can stand like King Canute waving my arms all I like but the digital download waves will keep on coming – as many music consumers and enthusiasts are now downloading music onto their computers – MAC or PC – and are listening to music that way, feeding it via a USB cable into a DAC and then into their HiFi amplifier and this is where the AMR DP 777 digital to analogue converter comes in.

The AMR DP777

The DP 777 is very much a tale of two cities, on the one hand we have the old world charm of red book CD digital and in the other we have the bright brash and less substantial world of computer audio and its brightest star for quality HD audio. This DAC is in reality two in one with neither section being a compromise on the other.

The other trump card up its sleeve is that the DP777 is also an analogue and digital pre-amplifier with two RCA inputs to route analogue signals out to a power-amplifier. For my system and its level of complexity I would need more analogue inputs and at least one fixed level analogue output to feed my tape decks but for the modern audio enthusiast who does not use something as quaint and antiquated – their possible thoughts not mine – the DP777 will be more than all they will need with two BNC/XLR digital inputs, two RCA and fibre optic ones. The only obvious omission is a digital output to facilitate digital recording to a CDR or similar machine – also now viewed by many as quaint legacy technology.

The AMR DP777 DAC is broadly similar in look to all of AMR’s other products in the 777 range and build quality is to a very high standard with all parts fitting together well and all inputs and outputs solid and well mounted. The fascia is brushed aluminium with the AMR logo recessed on the left upper side and the model details on the lower left side.

The middle of the DAC’s fascia is taken up with a large display screen taking up about a 3rd of it and its easy to read from quite a distance away. Below the screen are 5 touch buttons controlling power on off (stand bye), next two input selection back and forward, and the last two volume up and down if you are using the DP777 as a pre-amplifier.

The DP777 comes with a beautifully made all metal remote that gives the user access to altering the display brightness through four steps to off (I thought the DP777 sounded slightly better with the display switched off), and the following functions:.kHz/SAMPLING: to cycle through the different output frequencies. ZERO JITTER: for the highest sound quality. When engaged, a small “J” will be displayed. When the GMT Clock System dynamically tracks a change in the clock frequency, the “J” will flash. INPUT selection: to select the previous/next input.MUTE: to mute the output. AMR: auto-selection of the optimal settings for the best sound quality. Signal Polarity: hold down the AMR button for 2-3 seconds to change the signal polarity. HD Dual DAC selection: to select: HD DAC (best with 24/88.2kHz-192kHz recordings) or Classic DAC (best with 16/44.1-48kHz recordings). FILTER: to select: HD DAC: Organic / MP Listen / Apodising 808 / Traditional. Classic DAC: Bit-Perfect I or Bit-Perfect II. VOLUME Up/Down: controls the analogue volume control. Auto-bypass at full volume (0dB).

All in all the DP777 is a very well equipped DAC with plenty of features to try. I found myself after a bit of playing around that for listening I preferred the Organic setting both with the HD DAC and Bit Perfect 2 with the Classic DAC which is a broadly similar setting to Studio Master 2 on the AMR CD77.

There is a lot of technology packed under the hood and we will look at that next.


I will let AMR speak for themselves re describing the DP777 DAC I quote from their website:

‘High-Definition (HD) digital audio is redefining the quality of recorded audio for the 21st Century. Having created some of the most natural and captivating music sources on the CD standard, AMR has turned its attention to High-Definition audio and in its own imitable way, taken the road less travelled.

Our first objective was to deliver the maximum quality of music from the existent libraries of CD standard audio (be it on silver disks or as ripped lossless files) equally balanced with the requirement to also deliver the maximum music quality from the new HD audio formats. We meticulously auditioned the full array of HD DAC chipsets and whittled the field down to one of the latest and most outstanding.

Again, the standard textbook implementation was shunned as we applied the same assiduous design and execution of the multi-award winning CD-77 to unleash the full, latent potential of the HD format. Each stage of the signal path is a technical magnum opus focused upon one objective: the most enchanting and pulsating performance. The result is the DP-777 Digital Processor.’

‘The DP-777 has the same, unparalleled DNA as every other AMR component; with extraordinary digital advancements never seen before in any converter:

Gemini Digital Engine (GDE)* Unlike any other converter, at the core of the Gemini Digital Engine, there is not one, but 2 distinct chipsets that define their generation; one latest generation High-Definition 32-Bit DAC to produce the best sound from HD recordings and one Classic Multibit 16-Bit DAC to produce the best sound from CD. These two “non-identical twins” deliver the best of both worlds in a way that is simply unmatched. Further, the Gemini Digital Engine pushes these chipsets beyond what is thought possible. Using Field Programmable Gate Array (FPGA) and Digital Signal Processing (DSP) to handle the core digital duties, including the memory buffer and the signal processing, the outcome are two specially-commissioned DAC chipsets that perform well beyond the textbook.

Zero Jitter Mode* The Zero Jitter Mode utilises AMR’s ingenious Global Master Timing (GMT)* and Intelligent Memory System (IMS) to totally eliminate jitter coming from the source. The Global Master Timing clock system intelligently actualises over 28 million different real-time clock frequencies to exactly match the dynamic input clock down to 0.001Hz (i.e. ~0.04ppm accuracy) of the source. With this new and completely jitterless clock coupled to the Intelligent Memory System (IMS), the GMT/IMS system lock out source jitter once and for all.

24/192kHz Asynchronous USB Input The DP-777’s 24/192kHz Asynchronous USB Audio Class 2.0 Input is a true asynchronous decoupling of the DAC system clock from the computer that is also fully future-proofed.’

‘HD Valve Digital input (HD-VDi)* This is AMR’s atypical brainchild of using a New Old Stock (NOS) 6N11 high-speed valve designed to operate into several 100Mhz to amplify and purify the high-definition SPDIF signal with zero feedback. Clearly visible on an oscilloscope, with HD-VDi, the signal changes from a blurred to clean and sharp SPDIF signal. Any deficiency in the incoming SPDIF is completely removed.

OptiValve Output Stage Two NOS valves perform the left and right channel analogue amplification and output buffering duties using the same demanding approach as the CD-77/CD-777; where one half amplifies and the other half buffers without any negative feedback loop. No solid-state devices are present in the signal path.

High-End Pre-Amplifier The DP-777’s direct-coupled/buffered analogue pre-amplifier stage is capable of accepting two analogue sources in addition to the signal internal to the DP-777. The exceptionally precise 71-step resistor matrix-based Analogue Volume Control system delivers unmatched transparency. To attain the highest sound quality, no digital volume control is anywhere to be found.’

*: World’s first, AMR exclusive.

DP777 Features

Once again I will let AMR tell you about this off their website.

‘Gemini Digital Engine(GDE)®

Sonically speaking, the textbook implementation of HD DACs leaves a lot to be desired. This justified the decision to continue with the same innovative and comprehensive digital approach as the CD-777 and the CD-77 before that.

AMR’s HD Gemini Digital Engine is an ingenious implementation of two separate DACs; a HD 32-Bit DAC and a Classic 16-Bit DAC with Field Programmable Gate Array (FPGA) and Digital Signal Processing (DSP) to handle all core digital duties, including the memory buffer and managing the signal processing. AMR has in reality, created custom-built DAC chipsets to its exacting specifications which is akin to programming many discrete logic IC’s worth of circuit boards onto one chip. This approach is technically arduous and time-consuming, but is soon justified upon listening to just the first few notes of music from the DP-777.

Organic Digital Algorithm incorporating SMART®

At the top of AMR’s unique Digital Filter Algorithms is the “Organic Algorithm” which incorporates SMART®: (S)oft roll-off, (M)inimum-phase, (A)podising, (R)ingless, (T)echnology. This is AMR’s technical expertise at its very best where it has developed an original and comprehensive digital algorithm to address the sources of “digital ringing”; pre-ringing & post-ring in the recordings and in the playback of the DAC. Being the only manufacturer in the world with the “Organic” filter, in conjunction with the rest of the far-reaching digital and analogue implementation, the DP-777 is the first High-Definition DAC in the world that truly makes music to stir the soul.


AMR appreciates that “no one sound fits all” and that the highest quality of music reproduction is to ensure the original signal bit/sample rate is maintained all the way through. Hence, AMR developed the DP-777 with OptiSample® via both its High Definition and Classic Multibit DACs to ensure the original recording is preserved end-to-end.

The DP-777’s High Definition DAC offers: Organic, MP Listen, Apodising 808, and Traditional digital algorithm modes.

Under the DP-777’s Classic Digital DAC, the DP-777 offers: Bit-Perfect I and Bit-Perfect II filter modes.

All are all user-selectable, via the remote control and offer different perspectives on the sound but most important of all, reproduce the original recording to the highest degree.

Global Master Timing®/Intelligent Memory System®

Before the arrival of the DP-777, the issue of solving jitter introduced via SPDIF using a Phase Locked Loop (PLL) Clock recovery was seen as sufficient. However, this analogue “solution” to a digital problem is woefully inadequate yet is not even commonplace.

AMR’s Global Master Timing (GMT)/Intelligent Memory System (IMS) represent a total “out of the box” systematic digital solution that solves the digital SPDIF jitter issue once and for all. The Intelligent Memory System holds a large number of complete audio samples, so it may completely absorb a large amount of variation (jitter and drift) in the incoming signal, while still sending out data at a fixed and precise clock rate, regardless of variations in the incoming clock.

Central to the GMT clock system is an ultra-low jitter, quartz-driven clock system capable of producing over 28 million different frequencies. When engaged, the GMT system intelligently and dynamically controls the clock that drives the DAC chips and takes the data out of the memory buffer. The GMT Clock is set to precisely match the principal frequency of the incoming clock with a precision of better than 0.001Hz. Hence, if the frequency shifts from 192,000.002Hz to 192,000.003Hz over a period of minutes (drift) which is the minimum to be meaningful, the GMT clock will intelligently and precisely track the change.

Once the GMT clock has correctly calculated the incoming clock, the rate of updating the DAC’s clock with the minimal 0.001Hz step (~0.004ppm accuracy) step is at most, once every few minutes or less. As a result, the DAC clock is completely decoupled from the source and completely stable.

With the GMT clock that drives the DAC Chips and to clock the data out of the memory buffer at the same exact frequency as the incoming clock, there is nil jitter in the source clock, as there is no physical PLL link between the source clock and the clock driving the DAC Chips.

The GMT System is not a secondary PLL as used in some cases and some DACs since the late 1990’s, but an entirely new concept. Instead, GMT is a system that will completely block jitter and only react to compensate any slow drift in the clock source or to adapt to a change in sample rate.

The GMT Zero Jitter mode is available for all digital inputs including the USB input and is the new clock standard reference for the digital audio world.

Asynchronous 24/192 USB Input

The DP-777’s Asynchronous USB 24/192 means native and future-proofed playback on OSX and Windows.

Asynchronous USB 24/192 uses USB Audio Class 2.0 in Asynchronous Mode and is fully compatible with USB 2.0 and USB 3.0. It should be keenly stressed that USB Audio Class 2.0 should not be confused with USB 2.0. USB Audio Class 2.0 is required to support sample rates above 96kHz (that is, high-definition music). AMR is one of a handful of companies to have brought such a standard to market following the industry definition of the USB Audio standard.

Most USB DACs do not follow the global USB Audio standard and hence will require drivers for all PCs (including Macs, Linux) which may be unavailable and must be supplied by the manufacturer into perpetuity, for each new operating system.

By comparison, USB Audio Class 2.0 is built into Mac OSX and many versions of Linux and supported by Microsoft on Windows and is set to be recognised as an industry-wide standard to achieve native “plug & play” support in all future operating systems.

Asynchronous mode means the clocks are on the DAC side and the PC is synchronised to that stable clock. Compare this to the common way of USB audio workings where the DAC attempts to synchronise to the PC using a jitter inducing PLL to follow all the PC’s clock changes, be they caused by software directly modulating the clock or indirect clock modulation due to the varying processor loads (this is called software-induced jitter).’

‘By combining our Asynchronous USB Audio Class 2.0 connection with the Global Master Timing/Intelligent Memory System we are not only delivering future-proof, cutting-edge computer connectivity with virtually nil jitter, but we also completely remove the jitter of the clocks.

Crucially, the USB signal is completely decoupled (i.e. isolated) from the DP-777. So any power supply noise, RFI and ground noise from the PC is not able to enter and contaminate neither the DP-777 nor its signal.

Bit Perfection®

Presently, virtually all CD players and DACs are NOT “Bit-Perfect”. Such machines are only “Bit-Perfect” at the input interface section. None are truly “Bit-Perfect” end-to-end because the use of traditional digital filters will artificially manipulate the signal and the sonically damaging artefacts that result is readily detected by the human hear. Any DAC using oversampling (to any frequency) or asynchronous upsampling is NOT Bit-Perfect.

The DP-777 is one of a select few able to deliver a true, “Bit-Perfect” signal all the way through to the output as it preserves the signal integrity from the input (SPDIF/USB) right through to the pure valve analogue output stage.

HD SPDIF Inputs with Valve Digital input technology

The Compact Disk standard was never conceived with the notion of distinctly separate transport and DAC sections but once this became so, SPDIF was adopted as the method to link the two together. However, SPDIF is an analogue transmission system that uses what was originally a video signal format to transmit a digital system. Clearly, this is not an elegant solution as the SPDIF clock and signal are transmitted together as if the red, blue and green signals for a television were cobbled into a single run.

At AMR, to overcome this set of essentially analogue problems we devised a completely analogue solution. AMR’s proprietary Valve Digital input technology (VDi) is a world’s first: it is the use of the NOS 6N11 (high-speed valve operating into the 100MHz region) in a zero feedback circuit derived from military radar technology to re-establish the clean waveform of the original incoming signal from the two HD SPDIF Inputs.

Firstly, this ensures that even if the input SPDIF signal has an incorrect output level or poor waveform, the SPDIF input receiver will have a clean and perfect SPDIF signal to lock onto.

Secondly, as all SPDIF receivers use Schmitt Trigger input circuitry, the receiver will create a glitch noise at the trigger point, this noise travels back into the SPDIF cable, returning to the source component. It is this errant noise that is at least in part responsible for the major differences between SPDIF cables and sources in the input system of common DACs. As the HD-VDi isolates the SPDIF receiver from the outside world, HD-VDi eliminates the detrimental effect caused by this noise once and for all.

The DP-777’s HD SPDIF inputs employ a NOS valve input circuit for everything all the way up to the 24/192 high-definition standard. The result is clearly visible on an oscilloscope as the SPDIF signal is restored back to its perfect wave form. This input ensures the “right note at the right time” to give the music the “life” that is missing from all other DACs.


AMR believes that having the ultimate in digital execution would count for little if the analogue section was not just as committed. Hence, the analogue section of the DP-777 utilises AMR’s OptiValve® analogue stage with zero negative feedback and NOS 6H1n-EV valves. The “EV” designation represents the premium version of this valve. Being a double triode per channel design; in the DP-777, one half amplifies and the other buffers. Rectification and filtering in the DP-777 uses zero-noise Schottky diodes with additional noise filtering, an electronic inductor and a virtual battery design. The analogue stage of the DP-777 is identical in concept and function to that of the CD-77. With no operational amplifiers or solid-state devices, this is a major factor behind the DP-777’s organic and “vinyl-like” sonic performance that will embarrass many a high-end DAC.

Direct-Coupled/Buffered Analogue Volume Control®

The DP-777’s Direct-Coupled, Buffered Analogue Volume Control (AVC) system is AMR’s ground up analogue volume control system that is both transparent yet dynamic across the whole 71-step range. The AVC gives a completely noiseless change of volume and virtually nil distortion but with more steps and finer resolution that betters even the best stepped attenuators. The AVC functions as a series of near perfect switches, with no ageing, no degradation and no wear. It is finely adjustable in 1dB steps but the beauty is the extreme transparency that is second only to the famous transformer volume control (TVC) approach first developed by Western Electric at the turn of the century. Partnered with a fitting power amplifier such as the AM-77 or AM-777 (in Power Amplifier mode), the signal path does not get any shorter, rendering the music virtually palpable.


AMR’s expertise in specialised transformer design for audio use has led to the development of transformers with individual windings that offer the sonic benefit of individual transformers without the space demands. Again, AMR has shunned the mainstream (and more cost-effective) approach to the use “off the shelf” transformers, preferring to have its own dedicated transformers, with multiple layers of shielding built-in, hand-wound and hand-made. Power supply is an integral part of circuit design and AMR’s steadfast approach has ensured the highest possible quality of music performance.

The Finest, Cherry-Picked Components

‘Underpinning the design of each and every AMR component is the use of premium components which were selected after careful evaluation and exhaustive listening. These include AMR silver leaf capacitors, Sanyo Oscon capacitors, precision wire wound resistors, 70um gold plated military-grade printed circuit boards, AMR’s own German-made premium film and foil capacitors, power supply polypropylene film Music Capacitors and zero-noise Schottky rectifiers. We positively encourage a closer inspection of the DP-777’s internal components.’

All fabulous looking and on paper sounding stuff but how does the DP777 DAC sound in reality? Let us see….

Review System and set up – a Journey of Discovery

For this review while my system didn’t change much I had to change my attitude about computer audio and thus throw away a lot of prejudice. Right from the off I decided to take the tiger by the tail and go for broke and thus review the DP777 both with a red book CD transport and a computer – in principal an easier thing to decide to do than it was in reality.

I am not the sharpest tool in the box re computing, I know enough html and the functionality of this site to run it with minimal help from my wonderful service provider but when it came to setting up a computer to act as a source for the DP777 that was a very different matter. I am however blessed with a very technical friend – thank you Lisa – and I am also very grateful for Vincent Luke of AMR and Simon Bennett of Absolute Analogue for their aid in preparing the computing infrastructure for this article.

However a number of issues confronted me right from the off and they were as follows: Which computer to use and would lower or higher specification make a difference re performance, environmental noise, USB cable lengths and quality? Which Media engine to use? To deal with the first issue I found rapidly that computer spec does indeed make a difference re the smooth running of the Media Engine used.

The two main ones that AMR recommend for use with the DP777 are J River 17 (now in 18 version for Windows8) and Winamp – they do also suggest I Tunes as well – and one Media Engine requires much more computing power to run smoothly over the other, or so it seemed.

J River is a wonderfully slick, very adjustable program that I found to be a joy to use once I had figured out it would only run smoothly on my fairly new Sony laptop (learning is a wonderful thing all will be revealed later on) as using J River with an older Acer notebook would after about an hours use result in drop-outs, some stuttering and eventually silence. When that occurred I had to go back into the control panel of the laptop and re set the AMR driver – ASIO based – to start the music again.

Using Winamp a much less complex Media Engine caused the Acer no issues but sadly Winamp for this application was less easily optimised in particular re ASIO set up – and yes I tried the Makio WASAPI ASIO plugin but alas it was infected with a virus so I was unable to try Winamp in full octane mode so to speak as the ASIO plugin they have available directly through them offers no adjustment at all – via my set up anyway – and would not play properly with 192 music.

Having spoken with Simon Bennett of Absoloute Analogue he explained to me that some laptop/desktop USB set ups can cause issues especially when using USB in from an external HD and USB out to the asynchronous USB input of the DAC. The issues he explained occurred as a result of the paralleling of the outputs and it would be better to break this chain by using say a Firewire output on the computer to the DAC (if equipped with such) or use a Firewire equipped HD drive and hook it to the Firewire input on an computer. Not being able to do this I decided to break the chain and try the SPDIF output on the Acer – not a coax but optical output – and after purchasing a suitable adaptor I gave this ago, and while the fibre optic method of data transfer won’t support 24/192 it did 24/96 quite happily.

I tried this configuration with Winamp first and there were no issues with sound break up, stuttering or silences and all in all this form of hook up sounded very good though not as good as J River had – when working – so I tried J River next.

Firstly I had to switch from the ASIO setting on Winamp – as this produced no sound – but switching to direct did. In direct comparison to Winamp J River was a bit louder but after compensating for that I felt that J River was the slightly more transparent, open, detailed and dimensional of the two media players, plus it played all the file types I had to hand whereas Winamp was unable to play some.

I still felt that the Acer laptop was perhaps still not quite up to spec enough to act as the middleman in this application, as a few stutters still occurred over several hours playback. As a left field thought I pressed into service an older Windows 7 Fujitsu laptop which shock horror played every type of file perfectly. I literally scratched my head and rubbed my beard in perplexity and wondered was something else screwing up the Acer’s play back ability.

However once a few issues where sorted out (see 1) I was able to use the Acer again with confidence, as no further issues for the whole review period arose – and it acted as middle man flawlessly – and I am still using it. I did briefly go back to using my Sony laptop but despite a slight improvement in sound quality obtained by linking the Freecom Hard Drive via an esata connection (I feel and others like the aforementioned Simon Bennett of Absolute Analogue feel that breaking the USB chain is a good thing if one can and the esata connection did that) with a Belkin lead I opted to stick with the Acer as the Sony is my day to day computer – I am writing this review on it – and I wanted to keep it free from being a music source.

Once stable playback was achieved consistently I could begin the review properly and that was the plan until a major life changing event occurred out of the blue.

A Pause

Just as I was beginning the more focussed listening sessions I feel ill with a very bad Flu that kicked the crap out of me and my Dad died suddenly from a massive heart attack – while he and I were talking on the phone and he was asking how I was – during my illness so the review and my life was paused for awhile and only resumed more recently. In the mean time I did do some more casual listening but it was half hearted and my review hat was well and truly locked away. The change in this came when a previously agreed review with a deadline (The Wireworld USB cables) really needed done (promised schedule) and so I began listening to the AMR DP777 more seriously again as part of that review and then the iFi Audio USB Power review which followed that one.

In reality the pause was a useful thing re the review as I learn’t more about optimising the Acer and the computer audio set up in general and thus a few additions and tweaks were made in the new year.

Further Optimisation

One of the main ways in getting the computer in my case the little Acer race tuned was to remove all surpfluous programs and as mentioned earlier removing a conflicting program and at Vincent of AMRs suggestion I downloaded Fidilizer (2) which can be used to suppress Windows functionality which is not focussed on music reproduction. I used this excellent freeware in audiophile mode as using it in its extreme form which shuts down some extra Windows functionality in the laptop that I found useful to have. Was there a difference in sound using extreme? Yes but only a slight one. I also found putting Bright Star Audio Isonodes isolation pucks under the laptop and the hard drive was also beneficial. The one big tweak I tried successfully was trying to improve the performance of the laptops PSU.

Now I am well aware that the quality of any PSU can have a big impact on overall performance in dedicated audio components but I was sceptical re laptop PSUs but I replace the mains cable to the Acer with a Mark Grant 2.5 into a clover leaf IEC adaptor which improved things but pressing an old EC Audio Pandora’s box mains filter into use brought about quite a marked improvement in sound quality. I plugged the cloverleaf adaptor directly into the Pandora’s box and the Acer’s PSU into it – with support below the PSU as other wise it would have been floating in mid air and possibly straining the cloverleaf adaptor by its weight. Replacing the stock PSU with a specialist custom linear one might have raised the bar more but not having one to hand I was still very happy with what the Pandora’s box brought to the party.

The next biggest improvement despite the DP777 not requiring any power for the USB digital input was adding the iFi Audio iUSB Power the full details of which you can read in the dedicated review of those items.

Doing all of this plus running the same USB cables from hard drive to laptop, then into the DAC directly or into the iFi Audio iUSB Power brought about further improvements.

The extra hours casual use on the DP777 was also valuable, as AMR and others feel this product like other AMR 777 series – like the 77 series also – need about 500 hours run in/use to reach their final stable sound.

Listening System Additions – further Evolution of a computer audio system

Normally the reviews I write take place over a three month period or less and the system equipment ancillaries are fairly fixed and stable coming from my own collection of equipment and accessories, I will however tweak add things to get the best out of the item in for review – though I do try to keep to the reference system when possible so as not to add too many variables to the review. However circumstances re this review were very different from normal so I hope dear reader you will forgive the somewhat evolutionary nature of this review. During this review I was very much doing on the job learning about computer audio as I went along and during the pause – mentioned above – a few extra items came along and as such – being beneficial to the review – were added to the review process and system.

Initially the ancillaries were a little more basic re digital cabling as I was using the supplied USB cable and then some Belkin Gold USB cables and despite the AMR DP777 still being new it was pretty obvious that the better over basic cables made a difference to the sound (3) After making the Wireworld Starlight cables my references I also reviewed the iFi Audio iUSB Power which also made a difference to the overall performance of the AMR DP777 so these items were made part of the review system.

Also added was a Mark Grant 8 way isolation mains distribution block which kept the computer items separate from the main system (4) which was also a worthwhile addition to the review system.

One other change of note was moving from a 2TB Iomega hard drive which was very noisy in use to a much quieter Freecom 2TB hard drive which had an esata output.

So during the main bulk of the review the system was as follows: Balanced Audio Technology VK300se integrated amplifier, Anthony Gallo Reference SA amplifier, Anthony Gallo Reference 3.1 speakers, Moon Andromeda CD player, Marantz SA7, Acer 1810TZ notebook, Freecom 2TB hard drive, HP 22 inch screen, Freecom 2TB hard drive, Ifi Audio iUSB Power USB power filter. Digital cabling: Wireworld Ultraviolet, Starlight Red, XLO. Analogue cabling: Atlas Mavros RCA to RCA, XLR to XLR, Atlas Mavros speaker cable, QED Genesis speaker cable. Mains: the computer aspect of the system was isolated via a Mark Grant 8 way distribution, EC Audio Pandora’s box hooked to the Acer. Main cables where Audience Au24, Analysis Plus Power Oval silver and Mark Grant 2.5. Equipment tables were Clearlight Audio Aspekt racks, SSC isolation platforms (I felt the DP777 sounded best on one of these in my system), Bright Star Audio Isonodes and Sound Mechanics M8 cones. I also used Telos caps to cover unused RCA and XLR inputs and outputs with some small improvement in sound but not as marked a one as was the case with the CD777.


Dead Can Dance – Into The Labyrinth

I used a fair bit of music during the course of the review but I used this album a lot both as a 24 bit 88.2 FLAC HD file and both the CD and SACD layers of the Mobile Fidelity album the file was derived from.

The Review Proper – at last!

There is a wonderful musical rightness to listening to music via the DP777. Tonally it sits to the slightly warmer side of neutral, but its not despite using valves overly warm, sweet or rich in a sickly way. Bass is tight and detailed and the mid and treble are open and detailed with just the right amount of detail and openness. The soundstage is wide and deep when its part of the recording but not much forward of the front plane of the speakers and rather than having an overly analytical presentation one could say the DP777 is very musical, rather than etched or harsh. As I grow older I much prefer the more musical approach than being riveted to my listening seat by a machine gun presentation or a mailed fist in a thread bare velvet glove. Etched, spotlit detail is not how I hear music, even live and therefore I just don’t understand how some prefer this type of sound – as its just that sound and not music.

Using the DP777 as a conventional Red Book DAC with the Moon Andromeda, Marantz SA7, Micromega Dialogue and briefly an AMR CD777 as transports was interesting as once again the various qualities of the transports and digital outputs revealed themselves with varying degrees of soundquality. None sounded bad but the Moon Andromeda and the AMR CD777 sounded best with the DP777 so despite the AMR DP777 digital input implementation the quality of transport used had a direct effect on the sound still.

I enjoyed the CD777, DP777 combination and I did wonder for a moment or two if AMR might bring out a transport only, but in this day and age of dwindling interest in the silver discs I guess not but it was fun to day dream about such a pairing.

Trying the USB input on the CD777 which I didn’t do when I had that player in for review – I had no facility at that stage to do so – was interesting and a very fine sound was to be had but the DP777 was vastly better with a wider, deeper soundstage, better instrument separation, greater weight and scale and a richer palette of tonality. However in saying that the CD777 used as a USB DAC was certainly very good it was just that the standalone DAC was better as it should be and was.

I spent a lot more time exploring High Definition 24 bit 88, 96 and 192 music than listening to red book CDs via the DAC and over the period of time I was formally reviewing the DAC I was as I have mentioned earlier also on a steep learning curve and I found a number of things that improved playback, so optimising your computer or MAC front end is vital to getting the best from any computer audio DAC and certainly the quality of music via the DP777 was much better at the end of the review than the beginning and this was not down to run in as removing or deactivating the things I had put in place reduced the listening experience.

No doubt a seasoned computer audiophile would have had all these things in place right from the get go but I didn’t and I found the process very interesting and rewarding re getting to where I am at now.

The Elephant in the room.

Many computer audio enthusiasts claim that CD is dead and that most computer audio set ups are better than most CD players. I left to last comparing the same track by Dead Can Dance on my Moon Andromeda, Marantz SA 7 against the fully optimised Acer, DP777 combination.

Using Dead Can Dance’s song The Carnival is Over both as an HD 24bit/88.2 track, SACD and CD – same source Mobile Fidelity (WPCB – 10076/SAD 2711) SACD of Into the Labyrinth – I listened to the DP777 DAC first and thoroughly enjoyed the track – one of my favourite pieces of Dead Can Dance music.

The DP777 reproduced the beautifully sensual ebb and flow of the track, with multi layered instruments occupying their own acoustic space with Brendan Perry’s voice front and centre possessing great strength, emotion and also well defined within its own acoustic as a three dimensional fully formed entity.

Behind and surrounding Brendan all the instruments were easy to hear and follow either as a whole or individually. Certainly as I had improved the cabling and rest of the computer set up this track had always demonstrated these improvements as layer upon layer of obscuring grudge was removed. I know the cleaned window is oft used as an analogy to describe these sorts of improvements but each stage of learning and tweaking brought about an improvement that resulted in the wonderful music I was hearing and very much enjoying.

However as track 4 slipped into track 5 I halted things to see just how much of the anti CD rhetoric I have been reading was valid so onto the Moon Andromeda went the SACD of Into the Labyrinth and the CD layer was played.

I guess those making sweeping claims for the irrelevance of CD as a format have not been able to compare their computer set ups to many CD players in the class of the Moon Andromeda as frankly the difference in sound quality was not subtle but these improvements might not suit all.

The Carnival is Over via the moon had greater weight, presence, air and space, instrument separation, dimensionality, texture, nuance and detail. The soundstage was wider deeper and slightly more forward and despite being a tad leaner tonally and louder once the level was adjusted to match the DP777 the Andromeda was still the better sounding source. However after a lot of comparison between the HD track and the CD I felt that the despite the obvious shortcomings – as there should be to my mind between a £3500 DAC and a £10000 CD player – there was a beautifully beguiling and musical presentation from the DP777 that despite not being as good in the hifi areas as the Moon more than held its own in the pure musical enjoyment stakes.

I next compared the Marantz SA7 playing the track as an SACD to the HD version of the track and the overall sound was much closer to the DP777 though the Marantz was still better and in similar areas to where the Moon had been. However the gap between the two was narrower and the Moon was still the more open and detailed device but truth be told the presentation in comparison to the AMR DP777 and Marantz SA7 was more the afore-mention mailed fist in a velvet glove – albeit a pretty thick velvet glove – to the more musical approach of the other two. I guess what one might prefer will depend on system matching and overall listener preferences plus how deep ones pockets are.

The bottom line though is I guess that the physical CD can sound better than the virtual digital music than some loudly proclaim to be better and the results of comparing CD to computer will depend on the CD player compared. I can see that many budget to mid priced CD players may be surpassed in sound quality by a computer audio source but the high end CD players I had to hand held their own and offered more but that more might not be to all tastes.

In theory the HD Studio Master I used of Into The Labyrinth should have sounded better than the CD and the SACD but it didn’t in the context of this set up but it did sound very musically enjoyable via the AMR DP777.

Trying the same trick for some albums I also had on 24 bit 192 (5) did result in a further narrowing of the differences between the Moon Andromeda and the DP777 computer setup but the Moon kept the lead still.


The AMR DP777 DAC is a wonderful piece of kit that has helped open my eyes, ears and mind to the possible quality future that HD computer audio music can offer and I loved my time with the DP777 so much so in fact that I bought the review sample of the DP777 and I think it a real testament to the quality of this product, in terms of functionality, build quality, design and sound quality that it was with the DP777 that I stepped into the future with it – a light to guide my steps.

I realise that some may feel a bit cheated that I didn’t review the preamplifier section of the DP777 but I felt it would offer too much of a change to the reference system and thus too much to be explored on this occasion but I will in the future explore this option, though for me in the context of my day to day system with its analogue sources and tape decks (no tape loop in the DP777 preamplifier section) the DP777 as a preamplifier would not work for me but for those more digital in their set ups it might well be a fantastic all round solution.

Its my personal view that the AMR DP777 is another landmark product from AMR (with the iFi Audio iDAC and iUSB Power they seem to be doing this a lot recently) and as such I strongly recommend it with the caveat of trying it in your own system before buying one.


Retail Price:£3500

Source of Loan: Manufacturer/distributor.

Manufacturer: Abbingdon Music Research http://www.amr-audio.co.uk/index.html

UK Distributor: Select Audio http://www.selectaudio.co.uk/

DP-777 Specifications:

Operation modes: High-Definition 32-Bit DAC • Organic: 44.1/48/88.2/96/176.4/192KHz • Apodising 808: 44.1/48kHz • MP Listen: 44.1/48/88.2/96/176.4/192KHz • Traditional: 44.1/48/88.2/96/176.4/192KHz

Classic 16-Bit Multibit DAC • Bit-Perfect I; no digital or analogue filter • Bit-Perfect II; no digital filter, sinc(x) analogue filter

Digital Audio Inputs:• 2 x XLR/BNC with HD Valve Digital Input technology • 2 x RCA/Toslink SPDIF Interface • 1 x 24/192 Asynchronous USB Input

Analogue Inputs:• 2 x RCA per channel

Analogue Outputs: • 1 x RCA/XLR per channel

Thermionic Electron Valves amplification stage:• 2 x 6H1n-EV / 1 x 6H11P fitted

Output voltage (Digital Full Scale): • >2V

Frequency Response:• 20Hz to 20 kHz +0.0, -0.5dB

Signal-to-noise ratio “A” Weighted:• >100 dB

Total Harmonic Dist. + Noise (THD+N):• <0.3%

Dynamic range:• >90 dB

Channel separation:• >90 dB

Power Transformer:• 32 VA Custom EI Transformer (Digital Section)

40 VA Custom EI Transformer (Analogue Section)

Power consumption:• Standby: < 1 W • Power on: < 60W

Rated voltage: :• 115/230V~ AC 50Hz – 60Hz

Colour:• Silver or Black

Dimensions:• 17.7 in W by 4.7 in H by 14.6 in D • 45 cm W by 12 cm H by 37 cm D • 57 cm W by 49 cm H by 25 cm D (shipped)

Weight:• DP-777: 25.4 lbs / 11.5 kg • Shipped: 34.2 lbs / 15.5 kg

(1) – In time using this combination I discovered that a program installed by the Acers original owner was creating a conflict re trying to decode audio codecs and thus was working against JRiver – thanks to Lisa for figuring this out. With this discovery I ended up stripping the Acer of all superfluous programs and to date it has as mentioned in the main body of the review run flawlessly but I still feel that using an esata connection between computer and external HD gives better sound (the Acer is USB only) so my main laptop the Sony sounds marginally better than the Acer but as its my main computer I have opted to keep the Acer in the music role until such time as I get a standalone dedicated audio only focussed computer custom built.

(2) http://www.windowsxlive.net/fidelizer/

(3) Full details re these revelations in the Wireworld Starlight and Ultraviolet review.

(4) Seperate review upcoming

(5) I am well aware that 192 does not guarantee anything re improved sound quality as is the case with other HD music, much depending on the mastering, transfer and source of the music but in the case of what I listened to the music being 24 192 narrowed the gap further between the AMR DP777 and the Moon Andromeda,

Further thoughts

Doing this review has been a real challenge to me personally as it has brought me face to face with a personal demon re the loss of physical playback media – a future I hated the idea of and indeed feared. The AMR DP777 review took me to the Rubicon and across it and I am now of the mind that a digital HD future is one I am no longer afraid of or indeed reticent about as its clear to me now that at least re sound quality HD 24 bit 88.2, 96, 192 music can compete with CD and may even be better (1).

Downloaded files can’t offer a tactile physical relationship as CDs, vinyl and tape can and do but at least there exists a possible future where sound quality is not a throw away lowest common denominator commodity but sadly that future will depend on record companies and increasingly artists feeling there is a market for high quality music and that can only come about if those that purchase mainstream music demand high quality full bandwidth recording.

There are a couple of sources for audiophile quality specialist music but sadly only one source for high quality downloadable mainstream and specialist music and that is HD Tracks in America (2). I say sadly because David Chesky for whatever reason some time ago decided to not permit any customers from the UK and possibly the rest of Europe access to downloads. Without this all UK computer audio enthusiasts can do is rip their CD collections and buy some of the audiophile music from Linn, Naim and B&W . Now I like quite a few of Naim’s and Linn’s artists but frankly it is the mainstream music that HD tracks sell – Van Halen, Yes, Genesis etc – that will help grow interest in high quality music and I don’t really include Apple in this as I suspect most users of Apples I tunes will not be that into HD soundquality and will be happy with MP3 quality.

This is the only cloud I see on my own personal horizon and the only thing that will keep me back from moving more into computer audio (I do intend on improving things for what HD music I do have) so I will be continuing to listen to physical media such as CDs, SACDs, vinyl etc until I can buy HD music easily – not entirely a bright future I feel but only time will tell where this journey ultimately takes me.


(1) I have since finishing the bulk of this review been made aware of the limitations of the laptop I was using (I did use a Sony VPCEB4E4E laptop too with broadly similar results) and suggestions have been made that getting more from the DP777 DAC is possible by using a music only focussed custom built computer, one that far outstrips the results I obtained via my fidelized laptops.

I await the opportunity to try that with great excitement as the suggestion has been made that the performance of my Moon Andromeda can be outstripped with such a set up. During this review I have learn’t that optimising the computer source can improve the sound so who knows what a custom music computer/server with an optimised USB output might achieve.

(2) https://www.hdtracks.com/

© Text and Photos Copyright 2012/2013 Adventures in High Fidelity Audio…..except for AMR, iFi Audio product photos and album cover. Copyright belongs with their original publishers.

NB No part or portion of this article may be reproduced or quoted without written permission or legal action may result.

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