26
Jun
11

AMR PH77 Phono Stage

An LP Collector’s best friend

For an audiophile who is into vinyl, half the fun is finding that illusive LP in second hand record shops, the other half of the fun is getting that LP to sound great. Here I won’t dwell on the first half but on the second. After 80 years of the LP record, there exists billions, yes billions of LPs out there somewhere – some long forgotten in some mushy storeroom collecting dust and fungus. Thanks to some audio publications back in the eighties, it has brought to the attention of collectors many ‘classic’ stereo (and some notable monos) LPs, which went from obscurity to notoriety.

The golden age of the LP is not today, where you have remastered 180gm virgin vinyl of some of these much-vaunted ‘classics’ but back sometime in the fifties to the early sixties – many are monos and some are early stereo recordings. Invariably, they are recorded using tube equipment, mixed using simple tube equipment and mastered using cutters driven by tube amplifiers. As a result, these records have a sense of liveliness and vibrancy in its sound, which was lost when studios went solid state. For real collectors, an original classic Decca, RCA or Columbia in near mint condition is worth many times that of a sealed and unplayed remastered 180 gm virgin vinyl replica.

In the early days of RIAA (1954), the standard used for equalization of the LPs, differs from one company to another. It was not until much later the industry adopted the ‘correct’ standard. As a result, when some of these old LPs are played back on a modern ‘correct’ RIAA curve, it sounds anything but correct. The dilemma for collectors is to find a phono stage that has all the equalization curves needed to bring these valuable vinyls back to life.

The British Library Sound Archive, the BBC, Germany’s Institute fur Rundfunktechnik GmbH (broadcast research) and various other organizations are in the process of archiving these records into digital music files for future use – Abbingdon Music Research has spent many years collaborating with these organizations to build the ultimate Phono Stage – the AMR PH-77.

The key element of the PH-77 is its extensive library of equalization curves offered – AMR claims it has 23 different curves! In addition to the ‘classic’ era curves, the PH-77 also offers ‘modern’ curves – to my knowledge, I have not come across any phono stage with such an extensive suite of features. How does a ‘DMM’ (Direct Metal Mastering) curve sound to you? It does a lot for me. For many years, most of the LPs hailed from Germany are DMM only and they don’t sound good – harsh and peaky sounding with lean bass. I am glad to report, for the first time, I hear DMM for what its worth – only through the AMR PH-77 phono stage and no other. But I am getting a little ahead of myself.

The PH-77 phono stage is one of the latest products from this UK based company. At S$17,500 it is not a cheap, value for money phono stage like the Lehmann Black Cube in any of its incarnation but a serious component in its own right. AMR claims the PH-77 will equalize and play every LP correctly. It is a full Class A, zero feedback, full tube design housed in a full sized chassis with what AMR calls a ‘virtual battery power supply’, fully dual mono with two independent power supplies, full valve rectification, C-core transformers and so on. In line with its intended professional applications – archiving old LPs, it comes with a built-in analogue to digital converter, which outputs the digital signal via USB output. In ‘normal’ use, the Analogue to Digital converter is powered off so there will be no electronic noise to corrupt the signal. AMR give very detailed instructions as to the process of transferring the music from your LP to your computer in their manual. The data stream should be both PC and Mac compatible but you will need to get some music recording software for your computer. I foresee the appearance of ‘audiophile’ grade USB cable soon!

AMR is famed for its ‘Optitrans’ power transformer design and here in the PH-77, it is a hand wound unit with low leakage – hence suitable for use in low level audio circuits. In a phono stage, this aspect becomes more important than ever. By being able to place the power supply as near as possible to the circuits elicits the best audio performance without simultaneously having the downsides of electrical interference.

Housed in an identical chassis as the other AMR components, I am surprised how packed the innards are. High quality proprietary components, especially the use of film capacitors ensures the unit performs beyond ‘Best in its Class’ performance. Electronic switching enables the unit to switch between the various equalization curves. Further customization is allowed with 32 steps resistive and capacitative loading for MC and MM cartridges. Interestingly, among some of the more unique feature is the selector switching between elliptical or spherical stylus, pivoted vs parallel tracking arms and mono or stereo cartridge. For more information on this, there is a sidebar somewhere within this feature.

Externally, the front mounted ‘power’ switch actually puts the unit in ‘standby’. The real power switch is behind the unit, just above the power cord. AMR suggest the unit be left on standby to enable for a quick warm up before a listening session. The unit offers a ‘direct’ non-switching input (bypasses the selector switch – for best results if you have just one source) with an additional 3 switching inputs so if you have a turntable that can mount more than one arm, this might just be one of your options. Both balanced and single ended outputs are offered.

I am sure among the readers here we would have skeptics as to what AMR claims really works. I must confess I am not a collector of those classic LPs, most of my music hails in the last four decades. So is the extensive feature set of the PH-77 would be of limited value to me? Or put it another way, apart from being one of the finest sounding phono stage I have laid my ears on, is there something the PH-77 offers that no other does?

Apart from the ‘standard’ RIAA stage, the PH-77 offers the aforementioned RIAA DMM stage and also an interesting ‘eRIAA’ for ‘enhanced RIAA’. The latter corrects for phase shifts – I am not sure if it means it corrects for the phase shifts that occurs within the recording itself or even correct for the playback system.

What I do know is the difference between RIAA and eRIAA is blatantly obvious and recording dependant – at the same time. Having both enable the user to switch between the two effortlessly, using the supplied remote, for the best sounding option. Using the standard RIAA as a reference, the PH-77 sounded involving, harmonically rich and full bodied. On eRIAA applied to the ‘right’ recording, all the elements suddenly snaps into place – the voice is more focused, enunciations more coherent, definition increases which helps to define the character of the individual instruments. On the ‘wrong’ recordings, the sound becomes drier and less involving. You would really have to suck it and see it if which is the right setting for you! Perhaps after which you may even mark on the LPs that needs either one setting or the other!

RIAA DMM setting is, to me, a god send! Having lived through many years of suffering through German DMM records, the PH-77 finally gets it ‘right’. I always wondered what’s the fuss about DMM – they sound dry, with peaky highs and light bass. Through a ‘normal’ phono stage, I think CD sounds better than these crummy DMM LPs! That is until the PH-77 comes along. I concede that for many who feel that seventeen grand buys a respectable music system and not just a phono stage, it seems like using a sledgehammer to pound a quarter inch long nail. The truth is unless someone else makes a phono stage with a RIAA DMM setting, the AMR PH-77 is the only option available for now.

So how does the RIAA DMM sound like? In short, very musical, very believable and certainly very listenable. A total transformation! The bass end is now weighty and had a powerful character instead of the weenie sound I am used to. At long last, the ‘correct’ equalization brought out the virtues of DMM recordings – a strong sense of space and perhaps in today’s context, even a little 3D. It has a vivid presence which makes non-DMM sounds muffled and congested in comparison. I am utterly spellbound! I won’t vouch for every DMM pressing will have this effect but I can certainly say I never heard DMM pressings sounded any better!

Now all that remains is some kind soul willing to loan me a couple of LPs from Decca, RCA and Columbia from that ‘golden era’ to complete my assessment of the PH-77? Till then, I would suggest even if you cannot afford the PH-77, you should give this remarkable device a listen, especially with a bunch of DMM LPs and hear what you have missed for the last 20 years.

Sidebar 1
Selector switching

This is a complex topic. To give a minimal overview…

Most audiophiles appear to believe that there is such a thing as “the ultimate cartridge” and “the ultimate arm” that always gets the best from all records. In reality this is not the case.

Originally LP’s (mono & early stereo) were cut with linear tracking systems and using “line contact” cutting methods (out of necessity).

They were played back using pickups with spherical needles and using pivoted (rotating) arms.

The difference between these methods of producing and reproducing the signal generated a range of distortions, which were early targets for improving the reproduction of music. One of the solutions, widely employed since the mid to late 1960’s was to pre-distort the signal cut into the LP so the distortions were compensated by an equal level opposite pre-distortion, the technique being called tracing compensator or tracing simulator.

Such LP’s (most from the late 60’s to the late 80’s) cut using a tracing (distortion) compensator will require a spherical stylus to play correctly, they sound distorted when played using line contact styli.

Line contact styli are in theory the best choice to play LP’s that ante- and postdate the use of tracing compensation, however using cartridges with such styli in conventional pivoted tone arms produce large amounts of distortion especially in the inner grooves where many classical pieces have the highest levels.

For LP’s that ante- or postdates the use of tracing compensation and for the use of pivoted arms it is probably best to use mild elliptical styli. If a linear tracking arm is available line contact styli can be used, however great care must be taken to adjust the vertical tracking for individual LP’s.

So it may be reasonable to have a turntable using a pair of pivoted tone arms fitted with suitable cartridges featuring (respectively) spherical and mild elliptical styli and a further linear tracking arm with a line contact stylus.

Armed with the knowledge behind the cutting history of LPs, one is now able to understand the need for different arms and cartridges, to correctly replay each and every record.

Sidebar 2
Analogue to Digital Converter
The signal undergoes RIAA equalization in the analogue domain before converted to digital via a 24/96 A to D and output through the USB.

Sidebar 3
RIAA DMM

In the mid-1970’s Neumann and Teldec developed a new cutting system called Direct Metal mastering (DMM) where the grove was cut directly into a metal foil, not into a lacquer layer.

This eliminated several plating steps in the manufacturing process, allowed for tighter groove spacing and more high frequency level. These differences in the manufacturing process and the different mechanical resonance behaviour of media the groove is cut into (hard metal vs. soft plastic lacquer) give DMM records a very different tonality to traditionally manufactured records.

Sonic differences exist even though almost all DMM records have been, to the best of our knowledge, equalised to RIAA standards (excluding East German Amiga/Eterna DMM records and occasional accidents in the East German cutting rooms when undertaking contract work for the West).

The sound from DMM records is often perceived as overly bright and forward. While this is not directly a result of the equalisation employed, the tonality of overly bright DMM records can made more well-balanced or even handed by gently attenuating the upper midrange and lower treble. The RIAA (DMM) curve implemented in the PH-77 is such an implementation.

It is strictly speaking not an international standard (such as RIAA & CCIR) nor a de-facto standard (the Enhanced RIAA curve is an example of a de-facto standard due to the equalisation built into the Neumann Cutting lathes), but rather, a replay adjustment to ameliorate this common sonic shortcoming of DMM records.

Sidebar 4
eRIAA

The frequency response of any record cutting lathe will fall at a higher frequency and become less efficient, hence a lower level of high frequency detail was cut into the LP at the time of manufacture.

The Enhanced RIAA EQ is an amendment of the standard RIAA that approximates closely the actual frequency response of the cutting system and compensates for this particular roll-off; bringing the missing level of high frequency detail back into the recording.

Sidebar 5
What happens when I listen to the ‘wrong’ equalization?

Of course, no damage will result. However, the true quality of the LP recording will not be fully realised.

For example, when played back using RIAA equalisation:

A Decca Stereo LP (UK mastered or pressed – correct equalisation: Decca EQ) or Deutsche Gramophon LP (Germany mastered or pressed – correct equalisation: Decca EQ), will typically sound bright and edgy with a recessed midrange.

A Columbia Stereo LP (correct equalisation: Columbia EQ) will typically sound boomy in the bass, lacking in warmth and body and overly bright at higher frequencies.

A European LP (correct equalisation: CCIR EQ) will sound dull, lifeless and lacking in detail.

Armed with this understanding of how equalisation affects playback, given the considerable investment in an LP collection and an audio system, AMR believes that at the outset, the correct equalisation for each and every LP should not be overlooked as it is just as important as the rest of the playback chain.

This article is contributed by Terence Wong from MOD AV magazine.

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