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AUDIOMAGAZINE: S.A.LAB ERATO PRE AMP AN MONO POWER AMPS SYSTEM

Prise: 4 500 000 ₽ (per system)

Reviewer: Artjom AVATINJAN

January 21, 2015

ONE OF THE ENTOURAGE

 

Two amplifying S.A.Lab combos — Erato we’re testing now and Ligeia we talked about in one of the previous AudioMagazine issues — have as many similarities as they have differences. The similarities don’t relate to just looks, size, colossal weight (Erato is enormously heavy) and the differences are not only in names and specs (power, type of tubes used etc.). Both objects of audio art may be called ‘made-in-Russia’ but with some reservations. A lot of components and several important schematic elements are of non-Russian origin.

AUDIO OPPORTUNISM

 

Explaining the idea behind Erato, Alexey Syomin stated his aspiration to create a single-ended filamentary amplifier with output power higher than Ligeia’s and other models’. Erato’s output power thus became a chunky 100 watts into 8 ohms. Prior to it Syomin used to construct amplifiers of low output power, as a rule no more than 10 watts. This he viewed as sufficient for most applications. But predictably the pendulum swung to the other side.

 

As he put it, "as soon as you finish something, the idea to create an ideologically different concept grips you. A lot of modern speakers represent a complex load for an amplifier: they need higher power to work properly. That’s why I decided to construct a more versatile machine."

 

Erato inherited Ligeia's design philosophy of sectioned transformers, divided cathode heating and stabilized DC voltage by means of chokes. "I tried stabilizing voltage with transistors or microchips but didn’t like the results.

 

The sound shifted to an undesirable side." In his other products Syomin followed the unwritten audiophile law of pure filamentary tubes and valve rectifiers. Wherever possible he used vintage components and special iron cores for his transformers. For Erato he decided to give up on valve rectifiers. Instead he went after Schottky diodes and Germanium diodes for the preamp. As a result the sound became sharper and quicker. Talking to Alexey I mentioned that the power increase itself played an important role in the end result. "But you can hear how the amplifier's sound is different at the same power level" he objected. I still think that one can’t brush away the sum of several factors and also—this may well be the main reason—the character of the output tube.

 

As we can see the ideology in this case deviated from “the only right one" — purist and audiophile. What are the other reasons for Mr. Syomin’s audio opportunism?

 

“This time I wasn’t going to use only non-Russian or old tubes. There are many Soviet tubes in the Erato. But I decided to install samples from before 1970 only in extreme cases due to physical degradation. By that time old equipment have reached the end of its productive life and the same could be said about the specialists for some passed away and others retired. That’s why modern tubes sound a little worse although there are some exceptions to this rule". The powerful output pentode working as a triode — the first fiddle in Erato's tube ensemble — was manufactured in 1962. This tube is a copy of a Telefunken model and was mass-produced in the USSR under the ГУ-80 designation by means of repair equipment from Nazi Germany. This equipment was no doubt subject to old age and wear”.

A STEP IN THE DIRECTION OF THE GOLDEN MEAN

 

The sound of Ligeia seemed calm, pacified by a lack of explosive drama, sharply individual and perhaps too beautiful if there is such a thing as an excess of beauty. Erato meanwhile was imbued by its designer with a more dynamic and far more neutral and academic voice.

 

"The ГУ-80 working as a triode reminds me of my favorite 300B. The sound of the ГУ-80 can be rightly called proper and neutral whilst most of the high-voltage tubes with high inner resistance are pretty specific i.e. not neutral. This time I paid attention not so much to the sound character and year of the tube manufacture as to harmonizing the entire valve set and finding parts that collaborated perfectly. Some driver tubes will work with three or four different followers but these combinations will all affect the sound differently and sometimes gravely so. It’s important to also by ear and perhaps primarily so find the preferred combination. My winning candidate as ГУ-80 driver was the 300B which opened up the output tube completely and created high amplification at the expense of the previous stage with very good linearity. I could have installed a 2A3 or other valve but the 300B performed well above these other options.

 

"I didn’t aim to drive the output tube with just a single stage as popular notions would like to enforce. It's impossible if one considers the 520V peak-to-peak voltages. Besides I think it's crucially important to remain within the maximum linearity zone of a given tube. Bearing in mind that whilst recording the signal is being subjected to multi-stage transformations, we have to admit that it doesn’t matter whether in an amplifier we have one stage more or less. The main thing is to make the devices perform linear and without distortion."

 

The anode voltages of all Erato and Ligeia tubes are stabilized. The five-piece architecture (preamp, two power amps and a pair of output transformers) here was used because of the necessity to get significantly more power from an accepted no-compromise concept where Ligeia had produced considerably less power (let me remind you that Ligeia’s power is less than half of Erato’s). The fact that 400 watts arrive at the anode of this output tube demanded complex and massive output transformers constructed as two separate units each the size of a small subwoofer weighing more than 60 kilos. Erato and Ligeia are otherwise identical in size and design except for a few small details. I call it the pedestal style. Looking at it you can't help but wonder where the statues have gone. Deep vertical grooves in the wooden armor associate us with the crenellations of a column or pilaster to add another classicist motive. It’s clear that the transformers couldn’t possibly fit inside the main mono cases. There’s no free space. Besides even without the output iron it takes four strong men (weightlifters?) to move these boulders about. The transformers are rated for 8kW of power whilst the feeding power is 3kW and the core section 80cm²!

 

The preamp was designed to work with long cables and low loads. Basically it’s a single-ended circuit with about 4 watts of output power. It could have worked as an integrated amp for fairly sensitive speakers. The Erato project relies on only the highest quality parts like specially selected tubes and paper-in-oil high-voltage Duelund capacitors (aluminum, copper and silver foil inlaid with thick paper soaked in pure mineral oil, with lacquer manufactured from natural materials). I mentioned how many of these elements are of non-Russian origin. The enclosures are made of tinted solid Ash by Belorussian masters. The lacquer doesn't hide but highlights the pores typical for Ash. Ligeia’s cabinets were made of oak, i.e. a structurally similar wood but of a darker shade. The output transformers (cores and windings) are of non-Russian origin too.

BOTTLES

 

Power amplifier

 

The mighty ГУ-80 pentode (Erato uses a Soviet specimen from 1962) is an exact replica of Telefunken's RS384 which was in active use by the Nazi Wehrmacht from 1939 on. This output tube works in triode mode with perfect parameters of 450W anode power, 500mA quiescent current and low internal resistance for a reasonably high damping factor into any load. This tube is very linear. The US VT-25 input triode (late 1950s) was designed and originally used as an output or driver tube in low-frequency amplifiers. It has high linearity and substantial initial current therefore it’s capable of driving any tube. Here it works as a 300B driver. Because of its high anode voltage and perfect linearity the 300В triode became the chosen output driver. The amp requires 480 V P-P from it, which is quite a lot of voltage. Erato's high-voltage power supply features modern tubes made in Russia's city of Saratov. The power supply stabilizers feature two 6AS7 (Canada, 1970s), two 6ж4с (Светлана, 1964) and four сг4 (1967).

 

Preamplifier

 

The WE310 pentode (Western Electric, USA 1939) was used in early cinema projectors to drive a 300В. Here this very linear tube works as a pentode whose second grid is stabilized parametrically. The main advantages of the current-production Bulgarian 40 output triode are high linearity of the volt/ampere characteristic and low distortion. The power supply stabilizers are two 6AS7, two 6ж4, two с201г (USSR, 1954) and two VR-150 (France, 1957).

THE CONCERT HALL

 

When I was listening to this amplifying combo for the first time it hadn’t been named yet (at the Moscow Hi-End Show it was displayed anonymously). Ligeia as you may remember was named after a nymph. To strengthen the tradition of naming audio devices after Greek or Roman goddesses I invited Alexey to consider Erato. That is the name of a muse belonging to Apollo’s entourage and supervising love poetry. ‘Father’ Alexey approved the corresponding record in the amp’s birth certificate without hesitation.

 

This is the second time a manufacturer approved the name suggested by me. The first of ‘my’ devices was manufactured by a German brand and, as it is now evident, became a notable success. The Erato system with its exciting sound stands all the chances to repeat it… But the success of the former amounted to the sum of ‘good sound plus big sales’. Erato — due to its exorbitant price — will probably be notable only for its musical talents.

 

Comparing Ligeia and Erato I must say that as listener I had more empathy with the latter. These amplifiers primarily deliver the beauty of replay and only secondarily their own sound ego — their music signature lacks coloring. On the other hand Ligeia came with its own very strong personality as though commanding the music to obey it. Yet this didn’t harm Ligeia in any obvious way. Writing about Ligeia and Lilt I noted their profound vocal expressivity which off the record I viewed as Syomin’s signature style. With Erato however this quality no longer dominated. The main musical dimensions — horizontal as melody and polyphony, vertical as harmony and color plus the third dimension as spaciousness — came off at such remarkable balance that I'd justly call it the golden mean.

 

Manufacturers of expensive tube audio worry incessantly about not letting their valves run wild. On precise if subjective acoustic scales they weigh the amount of notorious ‘tube sound’. Any excess detracts from realism and makes the sound loose and untidy. Undue lack however raises the valid question of why we'd bother with tubes at all. Erato balances these two extremes in a very artful and even artistic way. And in my opinion that’s exactly how it has to be done. This is really a neutral sound in the best meaning of the word.

 

LAST BUT NOT LEAST

 

Once Alexey Syomin called Erato his last amplifier though not literally to imply anything ultimate since he is a modest man. But after a short while he started sharing thoughts on a new amp based again on the ГУ-80 (he obviously likes this tube) in which he’d do something different. One way or another the proverbial ‘never say never’ doesn’t imply that one must say ‘always and again’.

 

In the end Alexey aspired to create something absolutely alien to any adept of tube technologies instead; a transistor mono amp. He already showed me some enclosures which weren’t easy to fit into the trunk of a large car. This won't be opportunism but plain revisionism.

VERDICT

 

In Erato many audiophiles will acknowledge a significant achievement in tube amplifier technology (the same holds true for Ligeia). The Erato system will be highly appreciated by the most demanding of music lovers but not at all approved by any ecologists. A single mono amp consumes almost 1kW after all. Yet I don’t believe that the agenda of any upcoming green conference would ever contain an accusatory lecture on S.A.Lab's Erato and global warming. To warm a listening room with tube heat is quite another matter. It makes a fireplace utterly superfluous...

 

S.A.Lab Erato preamplifier (4 500 000 rubles per system)

 

Specs [as published by manufacturer]:

 

Erato preamplifier

Output voltage: 12V

Frequency response (max. power), 50Hz to 45'000Hz

Output impedance: 9Ω

Signal-to-noise ratio: 90dB

THD (100 Ohm): 0.03%

Input impedance:<100kΩ

Power consumption: 370 watts

 

S.A.Lab Erato monaural amplifier (4 500 000 rubles per system)

 

Specs [as published by manufacturer]:

 

Output stage mode: Single-end class А1/А2

Output power (4/8А1, 0.4% ): 75/42 watts

Output power (4/8Ω, А2, 0.6%), 102/60 watts

Frequency response (max power), 10Hz to 40'000Hz -1dB

S/N ratio: 95dB

THD (half power): 0.08%

Output impedance: 0.5Ω

Sensitivity: 7.5V

Input impedance: 275Ω

Power consumption per channel: 950 watts

 

THE MUSIC

 

DISC1 Beethoven. Tripelkonzert (EMI 5C083-02042)

DISC2 Mozart. Exsultate Jubilate (L’Oisean-Lyre 411832-1)

DISC3 J.S. Bach. Konzerte BWV 1044, BWV 1055, BWV 1056 (Archiv Production 198 189)

DISC4 Beethoven. Symphony № 3 Eroica (Deutsche Grammophon 135 050)

DISC5 Super Bass. Ray Brown (Capri Records CPR 74018 CAPRI)

DISC6 Reflection of Bach. Jacques Loussier (Chrysalis Records FV41591)

 

SOURCES

 

Michell ORBE SE turntable

SME IV tone arm

Lyra Helikon pickup

Lyra Erodion step-up transformer

S.A.Lab Level Zero Phono phono amp

ProAc Carbon Pro Eight, Wilson Audio Sophia Series 3 speakers

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