AMR DP-777 DAC

Abingdon Music Research's new DAC, the AMR DP-777 (Available May 2011 €3,150, approximately $5,000) is quite unique and clearly impressive. In fact, we have not seen a more impressive set of specs elsewhere.  AMR gear is all the rage now in the UK - check out Audio World Show and Audiograb's Axpona 2011 which features AMR digital front end in significant number of rooms.

The DP-777 sports two separate DACs inside, so you can choose to listen to 32-bit high-resolution or classic Philips 16-bit DAC one (selectable via remote control). AMR claims the world's most advanced patent-pending Global Master Timing clock lock technology which intelligently chooses over 28 million different real-time clocks to exactly match the dynamic input clock , the DP-777 decouples the DAC system clock completely from SPDIF/USB inputs to eliminate jitter. The USB input is 192kHz capable and asynchronous.


Several user selectable digital filters (via a DSP chip) including Apodising, Minimum Phase, Linear Phase, Soft-Knee and Brickwall Filters under: 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz; 192KHz.

The input stage has 2 x 'HD' Valve Driven Technology (world's first) XLR/BNC SPDIF inputs (24/192kHz) plus 2 x 'HD' RCA/Optical SPDIF inputs (24/192kHz). The output stage is ofcourse tube and its defeatable resister step volume control is in analog domain.  There are also two analog input so it can function as a preamp!

Detail from its press release:

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 managing all the signal processing, we have in effect, created own DAC chipsets that perform and function at the leading-edge.

Zero Jitter Mode The Zero Jitter Mode utilises our completely innovative Global Master Timing (GMT) and Intelligent Memory System (IMS) to totally eliminate jitter originating from the source. AMR’s Global Master Timing clock system intelligently actualises over 28 million different real-time clock frequencies to exactly match the dynamic input clock e.g. 192,000.001Hz or 192,000.002Hz of the source. Coupled to the Intelligent Memory System (IMS), the GMT/IMS system block out source jitter once and for all.

192kHz Asynchronous USB Input The DP-777’s true 192kHz Asynchronous USB Audio Class 2.0 Input effects a genuine asynchronous decoupling of the DAC system clock from the computer.

HD Valve Digital Input (HD-VDI) This is AMR’s unusual brainchild of using an New Old Stock (NOS) 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 square wave. As result, any deficiency in the incoming SPDIF is hereby totally 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 loop feedback. No solid-state devices are present in the signal path.

High-End, Direct-Coupled Pre-Amplifier The DP-777 is also a direct-coupled/buffered analogue pre-amplifier capable of accepting two analogue sources in addition to the signal internal to the DP-777. The DP-777 has an exceptionally precise 71-step resistor matrix-based Analogue Volume Control (AVC) system that delivers unmatched transparency. To attain the highest sound quality, no digital volume control is used whatsoever.

AMR CD-77 CD player / DAC

UK-based Abbingdon Music Research's CD-77 is probably the most advance and elaborate CD/DAC that is based on the vintage Philips TDA1541A chip, considered by some - the absolute best DAC chip ever made.  

The unit comes with several different sampling approaches from AMR's proprietary Digital Master non-over-sampling filter to oversampling to upsampling, which are user-selectable.  Digital Master I and Digital Master II were developed by AMR and are exclusive to the CD-77 and its brother CD-777.  

All internal clocks are synchronized to the exceptional military-grade temperature compensated master clock module to avoid the creation of unwanted beat frequencies, reduce overall digital noise and resultant jitter.  The CD-77's OptiReg® digital power supply circuit has 14 specifically designed regulators, most of which are two or three-stage. Its transport mechanism is an in-house design based on the high-precision, reliable Sony K-series laser pickup mated to the musical Phillips CD-18 servo system along with a proprietary high-torque direct-drive motor. This is all housed in a very substantial CNC machined aluminium CD well with an extra-stable CD spindle and a CNC machined aluminium CD clamp. 

CD-77's power supply transformers have been designed in-house and are individually hand-made. They are some of the most advanced double C-Core transformers available. AMR claims that they surpass even the impressive R-Core transformers used in many high-end components and comprehensively outclass traditional EI and toroidal transformers used in many peer group products. 

Other high quality parts including Ultra High Speed RF, military-grade design printed circuit boards, German-made premium film capacitors, AMR's own power supply polypropylene film Music Capacitors, zero noise schottky rectifiers and FEP Teflon insulated cable with silver-plate copper conductors for chassis wiring.

OptiBus® USB digital input accesses the vast library of music from a computer, allowing it to be enjoyed to a far higher level than conventional personal computer audio systems.  OptiValve® analogue stage is a thermionic electron valve circuit. Using no negative feedback, with high gain, very low distortion and low output impedance together with new old stock thermionic electron tubes.

Specifications

Operation modes: 

• Direct Master I; no digital or analogue filter
• Direct Master II; no digital filter, anti-sin(x)/(x) analogue filter
• Oversampling 2X, 4x
• Upsampling 96KHz, 192KHz ( I am at a loss to understand why, since TDA1541 only does 16-bit/44kHz TDA1541A can accept sampling rates of up to 192kHz - 8x oversampling from 48kHz base data - without problems, albeit at 16bits resolution)

Digital Audio Inputs: 

• 1 x USB interface, 1 X S/P-DIF Interface (optional)

Analog Outputs: 

• 1 x RCA; 1 x XLR per channel

Digital Outputs:: 

• 1 X S/P-DIF Interface (optional)

Thermionic Electron Valves: 

• ECC81/12AT7 (NOS): amplification stage
• 5687/6900 (NOS): output buffer stage
• EZ80/6CA4 (NOS): rectifier stage

How about the price? If you have to ask - you probably can't afford it.