SALON AV: S.A.Lab Chimera Phono – Phono Preamp

Chimera Phono, the latest cutting-edge innovation by the indefatigable Russian manufacturer, is built based on the company’s original circuit with scanty noise and distortion. If the customer so desires, it can be made on nuvistors or miniature tubes, with equally high parameters guaranteed in both cases. The corrector is designed to work with any heads - MM and MC with different output.

Let's listen to different music with "Chimera" and components of the appropriate class.

There are lots of phono correctors on the market, in different form factors, with different consumer capabilities and different parameters. However on a closer look, one discovers that with all this diversity, most manufacturers only use four or five typical circuits with minor variations. Accordingly, it all sounds about the same. Does this suggest that nothing new can be created in such a beloved but archaic area?

It turns out that if you set a goal, you can come up with something that has never occurred to anyone before. And such an example is right in before us.

How to bring together vacuum and silicon

Let me remind you that the S.A. Laboratory, led by Alexey Syomin, produces amplifying equipment of various classes and purposes. Throughout the history of the company, many phono-stages have been developed, and not a single design has reused the previous one. And the new Chimera Phono model is no exception. Alexey showed us the circuit, there are only four cascades in each channel, but they are not simple, but double-storied — high-voltage bipolar transistors with strapping used as the load of triodes instead of resistors. For more clarity, we will ask the author himself to tell us about his latest product.

— The circuit is interesting, but what were you trying to achieve by combining tubes and solid state devices?
AS: Since I nursed the idea of making a phono preamplifier with power supply noise suppression down to -110 dB. I've been thinking about it for several years.

— What's the point?" The best records have a signal-to-noise ratio of about -60 dB.
AS: Well, let's just say that the task is to simultaneously reduce noise and distortion. Since any corrector has a large gain ratio, the ripples from the power bus are amplified, passed on to the output, and nothing can be done about it.

— What about batteries?
— We live in a modern world so who's going to fiddle around with them? Moreover, we need a high anode voltage. The hybrid circuit you saw has a THD+noise level of less than 0.0007% over the entire frequency range. If there is not a resistor in the anode of the lamp, but a current source, then it does not participate in the sound at all, it simply gives 5 — 6 mA of current, and the lamp "sees" an infinite load resistance. At the same time, its gain is equal to µ, i.e. the maximum possible value, in our case — 33. In this case, the load line is horizontal and distortion is minimal, but only if the input resistance of the next stage is several megaohms. For this purpose, a cathode repeater with high input and low output resistance is installed after the first stage. It also has a small input capacitance, which gives a wide frequency band, and you can load such a cascade with anything, for example, like we have — low-resistance RIAA correction circuits, they are faster.

— Such circuits have been known for 50 years, if not longer. And they are not much less noisy than usual. What's the trick?
A.S.: Well the trick is that noise from the power bus is introduced into the bases of the transistors of the anode and cathode current sources, and the amplitude is set by the dividers so that their outputs have the same amplitude of noise. But the tube inverts the phase by 180 degrees, so in the opposite phase, the noise is mutually compensated, and only the lamp's own noise remains at the output of the cathode repeater due to the shot effect, and it is very low. Moreover, compensation occurs not only at 50 or 100 Hz, but up to 100 kHz and higher. As a result, the output of the corrector with tubes is an unweighted noise of -85 dB, and with nuvistors of about -90 dB. In addition, there is no capacitor in the cathode of the tube, and due to local feedback, it becomes more linear. Such a cascade can also be a driver for a single-ended amplifier, for example.

— But why 6H23P, the tube is known to be very controversial in sound?
A.S.: I have developed a low-noise 200 V power supply, which is ideally suited for the 6H23P. In addition, its clone 6922 turned out to be an exact analogue of the 6C52H nuvistor, so the same boards are obtained for tubes and nuvistors. That is, in the same case and with the same power supply, it is convenient to compare their sound. In addition, the tube can be changed to your liking with RCA, Philips, Telefunken, etc.

However, there is a problem with the nuvistors — they are soldered without panels, and in case of failure of one of them, the entire board will have to be changed. But the owner of the phono-corrector can do this by himself since we send fully configured boards.

As you can see, the phono-corrector is made in the classic S.A.Lab design — the steel case with corner ventilation grilles is painted with car enamel. A potential buyer can order a color option from a fairly extensive palette. The large handle on the front is an input switch. There are three of them — MM, as well as MS with low and standard output voltage. The signal from the latter two is sent to step-up transformers with coefficients x25 and x10, respectively, which are wound with the thinnest pure copper wire with gold plating. The outputs — balanced and unbalanced — are also transformer-based.

«In the tweeter band, everything was clear and transparent, but not sterile — where the cymbals sounded aggressively, there was brightness, pressure, and a real blow to the ears.»

As with all brand amplifiers, there is an operating time counter, which is especially useful for tube devices.

I will not describe the internal structure of the corrector: anyone into the subject will see everything in the photo for himself. And the weight of 20 kg speaks for itself.

Vinyl in a cleaned-up format

The source for the tests of the corrector was the AVID Acutus Dark Line turntable with SME 309 tonearm and EMT HSD 006 MC cartridge. From the Chimera Phono, the signal was fed to the S.A.Lab Thunderbird SE preamplifier, and then to the Black Knight power amplifier. The acoustic systems are TAD Compact Reference CR1 stand mount monitors, which needed half an hour to show their true character.

To be honest, I myself am rather wary of low-signal hybrid circuits, preferring either lamps or pure transistors. Therefore, after installing the first Chicago Transit Authority press, I began to listen carefully, trying to notice any unusual artifacts in the sound. And in vain — it was not possible to notice any alarming moments. Although the sound itself seemed somewhat unusual in the first minutes, both in terms of microdynamics and the formation of the sound space. The Reference CR1 have tremendous resolution in the upper range, but they also failed to identify the slightest flaws there. In the tweeter band, everything was clear and transparent, but not sterile — in the part where the cymbals sounded aggressive, there was brightness, pressure, and a real blow to the ears.

«Bonham's drums are fast, with an unstretched attack, so the rhythm literally provokes involuntary foot tapping.»

The second point worth noting is the corrector's ability to clearly separate sounds in a complex picture. On "Discovery", an album by ELO with the beginnings of polyphony and a lot of spatial effects, it felt like the music came out of the speakers and everything that happened during the recording was literally repeated right in front of you. There were many timbral details and small nuances in the sound, but not graphomaniacally, but harmoniously musical.

On Stravinsky's "Petrushka", the plasticity of the presentation was clearly noticeable, thanks to which the work, that was not too easy to perceive, lay comfortably on the ear.

The depth of the bass was determined mainly by the capabilities of the monitors, but its structure is truly vinyl, and this is clearly the merit of the Chimera. The bass is fast, not monotonous, on Led Zeppelin IV it is pulsating and extremely rhythmic, not blurred. Bonham's drums are fast, with an unprolonged attack, so the rhythm literally provokes involuntary tapping of the foot. Whether this is due to the low-impedance RIAA circuit, I don’t know, but it’s simply impossible not to notice the corrector’s rapid fire in the lower band.

Of course, tying your feelings to the circuit of a particular device is a thankless and pointless task, but no one will doubt that the Chimera Phono is a tube corrector. The combination of low noise and high supply voltage gives a colossal dynamic range, and this is perceived by the ear as the openness of the space in which the musical event takes place. And even if relatively compact acoustics are used for playback.

Frequency range (±0-1 dB), Hz: 20 - 20000
Nonlinear distortion (20 Hz - 20 kHz, 1 V RMS), %: <0.0007
Signal-to-noise ratio (unweighted), dB: 90
PSRR (Power Supply Rejection Ratio): 170 dB (50 kHz), 110 dB (50/100 Hz) <10
Output impedance, Ohm: <10
Dimensions (HxWxD), mm: 175 x 480 x 390
Weight, kg: 20
Price, RUB: 1,300,000