AUDIOMAGAZINE: Phono Amp S.A.Lab Paris

Placed in a rack a Phono amp rarely attracts attention. Being a major element to an audio system that utilizes turntable as the main source, the Phono amp usually has small nondescript body and it's natural for audiophiles to hide it behind bigger and more presentable components. But the Phono amp designed by Alexey Syomin and named after one of the most elegant European capital cities can grace the most exclusive stereo system — not only with its stylish looks but also with truly luxurious sound.

Invaluable contribution

First let me remind you the problems that this intermediary between the LP cartridge and the amp has to solve. The fist — but not the most important — task for a Phono amp is to amplify the signal coming from the tiny coils of the cartridge to the level suitable for driving the input stage of a pre amp. The second task is to correct the gain-frequency response (that's why this component is sometimes called a Phono corrector). The necessity of such a conversion is dictated by the way sound is recorded on a vinyl disc. If you give the disc a close look through a strong magnifying glass you'll notice that its grooves do not appear as exact concentric circles. Their edges are quite uneven and tend to wind from side to side. The degree of the winding is generally defined by the low frequency constituent of the recorded signal. Therefore it's this area of the sound range that determines the highest possible density of the signal recorded on a vinyl disc (and the maximum length of a musical piece the record can contain). The manner the high frequencies are recorded also has some particular features. The point is that mechanical reader (a pickup stylus, a cantilever or a tone-arm) has mass i.e. inertia. This fact limits the ability of such a system to read high-frequency signals. Moreover, if the level of high-frequency constituent in a wanted signal is not large enough the signal will be masked by the noise inherent it the substance the disc is made of. To solve the problems mentioned above a specific method was proposed, in accordance to which the low-frequency level is artificially reduced while high frequencies are amplified enabling to increase the recording density and the sound/noise ratio in the high-frequency range. While playing the record back one has to conduct the reverse conversion i.e. increase the bass response and lower the amplitude of high-frequency sounds. Ideally this reverse conversion must look like a mirror image of the one used for recording. Here we encounter a heap of catches that turn an apparently simple matter into a major problem requiring unique approaches to its solution. The point is that a vague semblance of response correction standard was proposed by RIAA (Recording Industry Association of America) only in the middle of 1950s. Nevertheless even after the standard was adopted several recording companies used different equalization curves. Before that the correction was conducted by sound engineers in accordance to their own notions of what a 'proper' record should sound like. That is if you have records issued before 1956 the problem of their authentic reproduction is a complex but a very interesting one. RIAA curve didn't become comprehensive in part because in the faraway year of 1956 it dealt only with 30Hz to 15kHz range whilst the recording and playback quality gradually bettered which eventually caused the necessity to widen the range to be corrected. The new version was adopted in 1978 and got the name of RIAA-78 standard. The good news is that the differences between the correction curves used by different companies weren't radical enough to spoil the listening experiences. In other words: having utilized an averaged curve (a RIAA curve as a rule) in a Phono amp you'll get a majority of records reproduced in a satisfactory way. But for a connoisseur, a perfectionist of an experimenter manufacturers offer Phono amps equipped with the feature of choosing the correction curve manually or even constructing it. But the major effect upon the playback is caused not by the curve itself but the way the correction circuits are designed (we mean both component parts and schematic). That was what Alexey Syomin focused on while designing the S.A.Lab Paris Phono amp.

And here we are in the cozy listening room of Nota+ salon drinking coffee and Alexey is courteously answering my questions concerning this project.

Hand-made

«To this day three samples of Paris Phono amp were manufactured and all of them incl. the one you've tested are already sold. I have all the component parts and material to assemble two more samples. They will complete the Paris project», Alexey said.

In this case he is limited only by the material used which is not only expensive but also not so easily available. Any S.A.Lab device fully discloses the true meaning of the 'hand-made' term that is gradually becoming a true rarity itself. Paris Phono amp is no exception. Literally every part of it — from transformers and chokes to the stylish and intricately constructed cabinet — was created by Syomin's hands. I'd call its design a classic for tube audio: a solid sheet of stainless steel polished to a mirror finish comprises a low foundation for a quartet of vacuum tubes and five rectangular boxes containing signal transformers, power transformer and power source filter choke. The center of oblique faceplate is occupied by a large backlit power button; MM/MC-input switch is on the left side and on the right side there are channel level needle meters backlit by a warm yellow light. In the back one can see not only balanced and unbalanced inputs but also separate inputs for moving magnet (MM) and moving coil (MC) cartridges. All these posts are of the highest possible quality and the gap between them is wide enough to avoid any connection problems — even in case of thick and rigid cables. Both inputs and outputs have specific features that distinguish S.A.Lab Phono amp from any competitors.

Let's describe the outputs. Namely the MC output. It's designed in the best possible manner — using a step-up transformer housed in a separate box and connected to the amp by a proprietary S.A.Lab interconnect cable. Both transformer and cable are standard accessories to the Phono amp. In other words the MC input sensitivity is essentially the same as that of the second input for MM cartridge. I asked Alexey why he designed two inputs when it was quite possible to get by with only one to which an MC transformer could be connectd. In answer he told me that a pair of inputs enabled to use a turntable with two tone arms and two cartridges — MM and MC — correspondingly. It's no secret: cartridge of each type has its advantages and traits that dictate genre preferences — e.g. MC cartridge plays vocal and symphonic music better. And S.A.Lab Paris lets its owner choose the necessary cartridge by mere input switching. But why MC transformer was not placed inside the amp's body? "An average transformer could be placed inside the amp but it's impossible to hide a good transformer there". Yeah, you only have to look inside the amp's small but massive body to agree with this statement of Mr. Syomin.

Toroid transformers for the left and the right channel are wound with silver wire and placed into permalloy cups that have additional screening made of solid steel. Besides the amp's body being made of thick steel plates itself provides for screening the ambient electromagnetic interferences.

The output stage features four transformers, one pair working for the balance outputs and the other one servicing unbalanced outputs. In other words the outputs work in parallel. It's a useful feature: you can connect Studer tape recorder to balanced output and listen to the signal coming from unbalanced output via an (integrated) amp.

But the main feature of S.A.Lab Paris is the use of RL correction circuits. Unlike the vast majority of RIAA correction circuitry this schematic doesn't use capacitors, the fact that influences the sound in the most benevolent way. The flip side of the coin here is the labor intensity of inductance coil manufacture and high cost of materials: the coils are wound with silver wire on a core made from composite material manufactured in Japan.

The amplifying circuit is based on two pairs of double triodes 6SL7 and 6SN7 made in the Russian city of Saratov. However the circuit is compatible with all their substitutes and doesn't require any adjusting. Judging by the fact that these tubes are quite common the choice of possible substitutes is wide enough: from modern ones to vintage NOS tubes.

«Designing the Paris amp I turned down kenotron feeding because a kenotron working in an amplifier carries the heavies load and needs to be replaced regularly. It essentially becomes an expendable material. Instead the Paris amp features diodes with choke filtering, — said Alexey. — The choke is hand-wound on a core made from German steel. The same material is used for the cores of all signal transformers. L filters in the power source provide a very stable power response which is impossible to achieve using C-L-C filter. The Phono amp uses only point-to-point wiring whilst the low-power circuitry is protected by additional metal screens».

The acquaintance with S.A.Lab Paris innards gives an expert a real pleasure because everything is organized carefully and logically.

City of the Morning Calm

Each one of us has their own impressions about European capital cities. For instance, I associate London with foggy twilight, Rome with afternoon heat (when shadows deftly hide in a different dimension) and the French capital with a calm summer morning: the night cool haven't vanished yet and sunrays glide along the rooftops slippery with morning dew, lighting up the old-fashioned café and shop signs. Only in Paris such an early hour is filled with entrancing mixture of aromas of coffee and fresh buns; only in Paris bistros start working at dawn to feed the city dwellers hurrying to their jobs.

Apparently my impressions are similar to Alexey's. But above and beyond the fact that the lettering and the distinctive background of inscriptions on the face plate and the rear side of S.A.Lab Paris amp look like vintage signs in the French capital it is essential also that the very sound of the amp gives the impression of the abovementioned morning calm. S.A.Lab Paris doesn't try to pull the music apart into isolated nuances but creates a wholesome and harmonious picture. However the sound is filled with a great number of nuances: the ability to extract minute details from a record is another strong point of the amp.

Despite the fact that channel separation level can't be called record-breaking (see measured performance) which is quite normal for tube audio, the device builds a large-scale scene stretching far beyond the borders defined by speakers and places soloists and instruments accurately. Detailed highs and luxurious middle is supported by a sufficiently deep bass. Meanwhile there is no hint of coloring; crisp delivery and audible articulation reveal a lot of new details in the seemingly familiar passages.

Total lack of synthetics and artificiality is noticeable immediately; the reproduction is absolutely open and effortless. Masterful delivery of the piano timbre and careful treating of vocals is accompanied by an ability to assuredly sustain rock and roll rhythm and impact. Heavy blues' energy and tenacious tempo reproduction is as effortless and expressive as is the polyphony of symphonic orchestra or vigor of electronic tracks. Audio scene not only opens far beyond stereo base, but is also notable for high vertical resolution. Bass remains clearly defined and resilient even in the lowest region of the specter and high frequencies entertain listeners by being crystal clear and exceptionally detailed. If one tries to find the tiniest fly in this barrel of ointment it's possible to quibble over a slight brightness while playing back modern vinyl. Tom Petty's Hypnotic Eye album is recorded with such prickliness that it is perceived as something overly rough. But old records only benefit from this manner of highlighting the high frequencies and these records usually comprise the lion's share of an average vinyl collection. Besides it is Bryston B100 SST2, our test bench amp that isn't notable for overtly delicate sound, that is instrumental in creating the brightness we've mentioned above.

MEASURED PERFORMANCE

S.A.Lab Paris Phono amp works over a wide frequency spectrum not limited to the hearing range (Fig. 1). But in the hyper acoustic area the frequency response deviates from the standard curve. Signal amplification diminishes too intensely, and the roll-off reaches 3dB at 24.5kHz. The correction doesn't completely comply to RIAA standard in the high frequency area of hearing range too (Fig. 2; left and right channel with frequency response corrected). Inter-channel imbalance doesn't exceed 1.2dB (a moderate value). Signal specter at 1kHz is shown at Fig. 3. TDH is about 0.21%. Similar values were obtained for other frequencies at 1V of output signal.

Фонокорректор S.A.Lab Paris (416 000 rubles)
Technical specs [ as published by manufacturer ]
Supported cartridges MM / MC
Correction sircuit RL
Frequency responce (RIAA) 20Hz—20kHz
S/N ratio (for ММ cartridge) 80dB
S/N ratio (for МC cartridge) 80dB
THD less than 0.1%
Sensitivity (for ММ cartridge) 5 mV PP
Sensitivity (for МC cartridge) 0.3 mV PP
Input impedance (for ММ cartridge) 47kΩ
Input impedance (for Мc cartridge, 1kHz, on transformer's side) 5.1kΩ
Output impedance 20Ω
Output voltage 1V (RMS)

THE MUSIC

«Baltazar Benitez Plays the Guitar Music of Astor Piazzolla» (LP, B00E0LTHVI)
«Paco De Lucía Plays Manuel De Falla» (LP, Philips, B00L81L5AO)
Jose Feliciano. «Sweet Soul Music» (LP, B006S8WTCA)
Jacques Loussier. «The Best of Play Bach» (LP, First Impression Music, FIM LP 010)
Santana. «Supernatural» (LP, Arista Records, LC03484)
Tom Petty & Heartbreakers. «Hypnotic Eye» (LP, Reprise Records, 543948)
Pink Floyd. «Endless River» (LP, Columbia Records, C-112629)

The main feature of S.A.Lab Paris is the use of RL correction circuits. Unlike the vast majority of RIAA correction circuitry this schematic doesn't use capacitors, the fact that influences the sound in the most benevolent way.

CONTROL COMPONENTS

Michell GyroDec turntable
Origin Live Encounter MK3a tone arm
Ortofon MC Quintet Black (MC) pickup cartridge
S.A.Lab MC
Bryston B100 SST2 integrated amp
PMC OB1i speakers
Interconnect S.A.Lab between step-up transformer and Phono amp
Analysis Plus analogue interconnect and speaker cables