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November 2011
The Boys from the West are back!!!
Pat has promised some enticing goods so we will be pleased to ogle what he brings.
Pat will be bringing a whole heap of electronics and presenting them in his usual great style. His company, WAR Audio, has a wide range of equipment (including the excellent Bakoon brand with some new products) and so we look forward to a terrific meet
Thank you Pat in advance for the great effort you put in each and every year.
“Everything old is new again ?”
Introduction:
At the October meeting we had a veritable audio smorgasbord.
Warren Marshall presented: Once Analog Reference Turntable by Vince Hamilton, Audio Origami PU7 pickup arm, a true classic cartridge hand-made by the owner/designer of ZYX – the Alpha-Genesis 1000, and pre-amps by Jasmin, JLTi (both solid state), and the Minimax Tube Phono Stage by Eastern Electric.
Digital source was the highly acclaimed Oppo BD95, taken to new heights by Joe Rasmussen’s JLTi Terra Firma upgrades. Amplification was a JLTi KT88 MkII Tube amp delivering 2 x 30 Watts.
Speakers were Orpheus Aurora Gen IV Standmounts and Orpheus Aurora Maximus Floorstanders – prototypes, developed by Brad Serhan and Joe Rasmussen. And the club’s KEF Q900 floorstanders.
The Orpheus speakers are notable in that the design approach taken by Joe in developing the crossovers pays close attention to the relationships between voltage and current feeding the drivers. This has resulted in a speaker that can be current driven.
Kids! Don’t try this at home!
It should be noted that driving a conventional speaker system from a current amplifier, or any high impedance, can render operation of the crossover almost useless. At the least, it causes a shift in the crossover frequencies that can result in driver damage – especially tweeters. This, and the lack of electrical damping, means the speakers will probably sound terrible.
Note: In the above context, a current amplifier is one where the output current through the load follows the input signal (usually a voltage). In a conventional amplifier, the output is a voltage also. However, the term current amplifier is often used in the hi-fi press and in sales brochures, erroneously, to describe an amplifier in which the feedback is applied at the amplifier’s input in the form of a current, injected into a low impedance, which has a number of benefits including wider bandwidth and lower transient distortion. Note further that this is still a voltage amplifier, because the feedback signal is derived from the output voltage.
The Meeting: Listening - Session 1:
Vinyl, JLTi preamp, JLTi KT88 MkII integrated amp, Maximus speakers.
Santana – Abraxas – Singing Winds, Crying Beasts
ELP – Works (I) – Keith Emerson’s Piano Concerto
Don McClean – American Pie – Crossroads
Ricardo Muti – Philadelphia Philharmonic Orch. – Musorgsky’s Pictures at an Exhibition – Hut of Baba Gaya, Gate of Kiev
4) cont. Infernal Dance of King Kastchei
Session 2:
We tried the KEF Q900. Contrasting the Maximus, these seemed very (sometimes painfully) bright, with peaky mids, but also more detailed and open. Bass was somewhat restrained (or “polite”), but that’s not to say a lack of extension – these could go very low.
Tracks Included:
Deep purple – Child in Time
Gina Jeffries – If This Is Love
Bella Fleck – Flight of the Cosmic Hippo Misery
On #2, the KEF midrange seemed to “shout” on vocal, and were a touch harsh – even tiring. But the bass was fast and clean – one could clearly distinguish each hit on the tom’s. I would prefer to wind the tweeter level down by 2-3dB. We then went back to the Maximus with Joe’s experimental current amp. These were based on the National Semiconductor LM3876 50W single chip amps, configured to output current rather than voltage. Output impedance was reduced to about 200ohm. While a true current amp has an infinite output impedance, this can cause instability. As 200 is much greater than the 8 ohm speaker impedance, it still behaves like current drive, and my previous comments apply.
We played:
Misery – repeat
Hippo – repeat
Track #7 is notable for it’s deep bass. We should remember that as well as switching from a voltage amp. to a current amp., the former was tube, the second used a single chip solid state amp; this in itself would result in different sonics.
Where previously the Maximus delivered fast, tight bass with exceptional control, now the bass seemed to overhang – it sounded “ragged”.
Switching back to the tube (voltage) amp., we played:
Bill Miller – Drums of ……
Hippo – again
Harry Belafonte – Hebrew Folk Song
Dave Brubeck Quartet – take 5
I noted sharp attack on drums, and very natural saxophone.
Conclusion:
There is absolutely no doubt in my mind as to the technical superiority of digital, and solid state, based on almost an measurement or test you care to name.
(Note to self – remember to buy bullet-proof vest and hire body-guard.)
But there can be no denying the magical allure, musicality, and sheer “listenability” (for want of a better word) of analogue (vinyl and tape) and tube systems. When one examines the considerable limitations of vinyl recordings – all the way from the velocity and amplitude limits of the cutting head used to make the master, the stamping process, the (undesirable) physical properties of the vinyl material itself, and issues involved in playback, such as stable rotation, tone-arm tracking, the drop in linear velocity from start to finish (by about half), and the challenges faced by the arm and cartridge itself – it’s a minor miracle that it works at all.
Put simply, vinyl just doesn’t have the right to sound anywhere near as good as it does!
But is it just about the sound quality?
You go to a fancy restaurant and order a very expensive bottle of vintage wine. The waiter presents the bottle to you, with dust still on the label as a testament to its authenticity. (Restaurants keep a jar of dust especially for this purpose.) You knowingly peruse the label, and to demonstrate your considerable wine prowess state: “Ah yes.. that was a good year…”. The waiter skillfully removes the cork, taking care not to leave a trace in the bottle, and pauses a moment for the wine to breathe, before pouring a small sample into your pristine, sparkling glass for you to taste. You examine it, smell it, and slowly taste, stopping just short of doing a full chemical analysis, before giving your approval for the waiter to fill all the glasses.
Could this wine possibly taste the same if it was poured unceremoniously from a screw cap bottle into a disposable plastic cup? No Way! And when you start reading the descriptive menu, you begin to salivate even before the food is ordered.
At the meeting, Joe took care of digital playback, using the excellent Oppo BD-95 which he had upgraded to even greater heights. He simply scrolled down the playlist, and clicked on the required track.
Warren looked after the vinyl. He would gently coax the record from its sleeve, tenderly place it on the turntable, lovingly caress it with the cleaning brush, ever-so-caringly apply the outer ring weight and 4kg centre weight, position the tone arm, and finally, with the precision of a surgeon, lower the stylus to the groove.
I was reminded of my love-affair with reel-to-reel tape, back in the 70’s and 80’s, and the way in which I would carefully mount the spools, threading the tape through the heads and a multitude of rollers, guides and tensioners. And of one of my first engineering assignments, developing computer synchronization of multiple tape transports used in film sound post production. Those beasts would rewind at frightening speeds, coast smoothly to an (almost) stop, and then drop into play synch’ed to within a quarter frame, all without a hint of tape spill or snatchup. I could sit and watch that electro-mechanical ballet for hours, transfixed and mesmerized.
But what am I saying? Coax, tenderly, lovingly, caress, caringly, love-affair, mesmerized? These words don’t belong in an audio report. But wait a minute – maybe that’s it. Maybe that’s the answer I’m looking for.
Because when viewed in this context, digital (sadly) is often little more than “wham – bam - thankyou ma’am”, whereas analogue is like being slowly and skillfully seduced by an experienced lover, while trembling and breathless, you peel off the lingerie.
