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Complete Catalogue of 23 Equalisations Curves

Contrary to common perception, the introduction of the RIAA Equalisation in 1954 did not result in all LP’s being cut using this standardised Equalisation Curve. Even as late as the 1980’s, several significant record labels (including USA ones) continued to use equalisation curves that differed from the RIAA suggestion. In addition, many original “all time classic” issues precede the widespread adoption of the RIAA Equalisation standard and so, require a particular equalisation curve.

All such LP’s cannot be reproduced correctly with a phono stage offering only RIAA Equalisation. The PH-77’s OptiEQ allows the selection of 23 different EQ curves in real-time via remote control. This covers all known LP vinyl ever pressed, a true first among reference phono amplifiers.

EQCurve

One may now finally listen to vinyl recordings the correct and original way such as:

  • The original Mercury Living Presence series (Decca FFSS, Decca FFRR EQ)
  • The original Deutsche Grammophon Classical records (Decca FFSS, Decca FFRR, CCIR EQ)
  • The original Miles Davis records (Columbia EQ)
  • Verve Jazz records, with performers like Charlie Parker, Count Basie, Ella Fitzgerald, Nina Simone and The Righteous Brothers etc. (Columbia & AES EQ)
  • The original Dave Brubeck Quartet records (Columbia EQ)
  • A significant number of the original stereo Decca (Europe) records (Decca FFSS, Decca FFRR EQ)
  • Rectify high frequency roll-off and excessive phase shift of all, including Neumann and Western Electric vinyl cutting lathes (Enhanced RIAA EQ)
This list* is far from comprehensive but sheds some light on how the magical musical performance of such coveted recordings has never been fully realised until now.

*: The labels on the list also issued many records based on the RIAA equalisation as well.

Unorthodox Signal Path Design and Bespoke Implementation

The PH-77 boasts only two gain stages that incorporate a total of 6 electron valves (3 per channel). It is a purist’s valve phono stage aimed at reproducing vinyl to the very highest level but with flexibility of adjustment of gain/load over a very wide range: The 1st Gain Stage is a hybrid comprised of one half which was adapted from "Advanced GAmma Tracking Array" (AGATA) pre-amplifiers designed in the UK. The other half is the NOS Mullard ECC81/12AT7 to form a fully direct-coupled stage with no negative feedback. Pure passive RC record equalisation2 (including the standard RIAA equalisation) is then performed using 26 silver foil coupling capacitors.

The 2nd Gain Stage uses the NOS Philips 5687WB electron valve for gain and to also provide a low output impedance for the PH-77 (<200Ohm). This stage has its cathode directly connected to the signal ground (no resistor or coupling capacitor). Bias is supplied by a fixed voltage. Following this, the signal is then passed through a directly coupled film & tin foil coupling capacitor of the highest quality to the output.

The PH-77 is a pure single-ended, class A, zero negative feedback design. All low level signal connections including the cartridge are coupled directly. Only two coupling capacitors are employed overall. One is a custom made silver leaf capacitor that follows the equalisation block. The output capacitor is the same German-made film and foil capacitor as used in the multiple award winning CD-77 CD-Processor. The circuit is designed to preserve absolute polarity at all gain levels and for all equalisation settings.

All valves used in the PH-77 are rare NOS valves, e.g. Mullard ECC81/12AT7(2 pcs), and Philips 5687WB(2 pcs), EZ80(2 pcs).

The EQ section (including RIAA) is made up of custom-made silver leaf capacitors selected to less than 1% tolerance. For the standard RIAA EQ, all parts are directly soldered into the circuit using silver solder. The parts adjusting the historical curves are then switched into the circuit by gold over solid silver contact relays to ensure the best possible analogue performance with all EQ curves.

In order to ensure that any remaining dielectric effects in the capacitors are minimised, all capacitors carry bias voltages many times that of the signal voltage applied. This unusual approach operates the capacitors in a mode that is similar to single-ended Class A operation for amplifiers, to attain maximum linearity at incredibly low signal levels.

The end result is a signal path that preserves the purity of the music that is second to none.

Dedication to Purity of the Power Supply

The PH-77 uses sonically superior valve based rectification with NOS EZ80 (2pcs) and 2 x double C-core 20H choke filtering implemented fully dual mono, for the absolutely best possible power supply quality.

Conventional power supply regulation, valve or solid-state based, invariably uses negative feedback, which frequently results in sonic degradation of the signal circuit.

Instead of traditional regulators, the PH-77 employs a far more elaborate set of 4 virtual battery supplies, which are characterised by zero negative feedback and lowest possible noise. These are followed by a further 28 stages of passive power supply filtering, 8 of them utilising very costly large value film capacitors for the highest sound quality.

The resultant power supply allows the delicate signal circuit to work unperturbed by any power supply issues, giving the PH-77 a supreme ability to convey the full dynamics and emotion of the music.

Finest Matching and Unparalleled Adjustability



In order to allow easy and precise matching of any cartridge, AMR has made the PH-77 adjustable using either the included aluminium remote control or via the front panel controls. The PH-77 offers:
  • levels of gain 72dB, 66dB, 60dB, 54dB, 48dB, 42dB, 36dB, 30dB for complete cartridge compatibility, optimally matching Cartridges with output levels from below 0.1mV to over 12mV.
  • 64 steps of load for pinpoint resistive and capacitive loading.
  • 3 switchable inputs to select the desired cartridges and tonearm combination, be it elliptical or spherical stylus cartridges, stereo or mono cartridges, fixed or flexible tonearms, linear tracking or pivoted with Moving Magnet or Moving Coil cartridges.
High-Resolution 24bit/96kHz Analogue-to-Digital Converter For Storing Vinyl to Computer

The PH-77 features a reference grade 24bit/96kHz Analogue-to-Digital Converter for the highest quality transfer/archiving of vinyl to computer. This is achieved through a direct USB connection to a personal computer for preserving the integrity of the signal. This feature means the PH-77 is one of the most powerful phono sources with which to transfer vinyl pressings into the digital domain.




Information and specifications subject to change without notice.

   
   
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