Yamaha RX-A8A amplifier test

A new "monster" in Yamaha's Avantage range, the 2021 RX‑A8A aims to convince the most demanding audiophiles of the contribution of multichannel listening realism. For this, this integrated amplifier relies on the experience acquired by the brand over the years and its mastery in terms of sound reproduction.

Yamaha RX-A8A, heir to the Yamaha DSP-Z11

Yamaha already offered in the Avantage family a system with eleven real channels of very high quality. It was the MusicCast CX‑A5200 preamplifier to which it was recommended to combine the MX‑A5200 power unit. However, having separate elements made wiring the installation complex. In addition, this separation of functions also caused a significant increase in the production cost of the system. For the purpose of simplification, Yamaha therefore had the idea of ​​combining these two elements into a single box, like the DSP‑Z11 (click on the product reference to discover the complete test of the product by the editorial staff of AVCesar.com) which appeared in the brand's catalog in 2008. Ultimately, the RX‑A8A combines the electronics of the MusicCast CX‑A5200 preamplifier and the MX‑A5200 power unit in the form of an integrated unit (see photo below with the CX‑A5200 preamplifier above the RX‑A8A and the MX‑A5200 below). Very high quality links capable of meeting both the requirements of the most advanced Home Cinema systems and listening in conventional stereophony.

Exclusive Yamaha technologies

To meet the expectations of the most demanding enthusiasts, the pre-amplifier section of the RX-A8A is equipped with exceptional technical characteristics. A Qualcomm QCS407 processor (see photo below) gives it further optimized sound behavior with support for Dolby Atmos and DTS:X immersive audio systems. The conversion of digital streams, for its part, is entrusted to an ESS Saber ES9026 Pro DAC 384 kHz/32 bits for the seven main channels. In addition, they also benefit from Auro 3D processing (via upcoming Firmware update). For flawless management of the most up-to-date Hi-Res Audio streams, compatibility with 384 kHz/32-bit Flac and Wav files is guaranteed.

To go even further, several treatments specific to Yamaha or its partners are also implemented. This is the case with ESS's 32-bit Hyper Stream (THD) processing, which optimizes dynamic range and signal-to-noise ratio, or D.O.P.G. (Dac on Pure Ground) responsible for reducing background noise. Specificities which further complement the digital optimization processing and also refine the quality of the silences as well as the resolution of the sound message to resituate the smallest subtleties.

Another major innovation, the RX‑A8A is equipped with Surround AI technology. This digital processing based on artificial intelligence algorithms aims to recreate virtual channels. It offers a sensation of magnified sound immersion. Integrated into the DSP, AI technology analyzes the soundstage, then creates complementary sonic immersion channels to provide excellent realism. This analysis made by artificial intelligence in real time takes into account specific and representative sound elements of each acoustic environment, such as dialogues, background music, ambient sounds and sound effects to generate coherent and complementary information to that of the existing channels. The system thus manages each channel as a sound engineer would do to optimize listening.

Objective Slew Rate

The fact remains that, within an "integrated", if the quality of the pre-amplification is essential, it is still necessary to associate it with power stages capable of exploiting fully its possibilities. For the power amplification of its newcomer, Yamaha has opted for a fairly conventional configuration. It revolves around eleven output stages that use push-pulls of power transistors working in Class AB. Each of them is able to deliver a power reaching 150 W and even up to 230 W under 4 ohms. The RX‑A8A will thus be able to tame the most rebellious speakers with great ease. In addition, to give it a lively and responsive temperament, these original power stages (see photo below) have a very high sweep speed (Slew Rate). A parameter which is rarely talked about and which deserves some explanation.

In fact, the slew rate of an electronic system corresponds to the variation in the number of volts per unit time that its output is capable of presenting. For example, if a device displays a Slew Rate of 10 volts/microsecond, this means that its output can go from 0 to 10 V in one microsecond. A parameter different from the notion of frequency response since it involves the amplitude of the voltage variation to be delivered. To take the previous example of our system with a Slew Rate of 10 V/µs, it will only take 0.1 µs to restore a variation of 1 volt, but 10 µs if it is 100 volts. Benefiting from a high Slew Rate therefore ensures a lot of reactivity to the system and, in our case, makes it possible to easily restore the marked pulse frequencies.

Type EI transformer

It should be noted that, while having output stages with substantial power is a fact, it is still necessary to supply them with energy efficiently to benefit from their possibilities. Here again, Yamaha has opted for a fairly conventional solution. The power supply of the RX‑A8A is based on a generously dimensioned EI type transformer. Admittedly, it would not be able to permanently deliver the energy necessary to supply the eleven channels simultaneously if they were used at their maximum power, in which case the total consumption would exceed 2 kilowatts! But its power is more than sufficient to supply all the channels under “normal” conditions of use, even at very high listening volumes and regularly calling on the maximum resources of the power stages.

Indeed, music is not a signal of constant amplitude but, on the contrary, is made up of alternating peaks of consumption and periods that consume less energy. In this mode of operation altering power calls and calmer periods, the use of very high value capacitors makes it possible to "smooth" the consumption of the power stages, which considerably reduces the consumption peaks and thus the power that deliver the transformer. To ensure this smoothing, Yamaha did not hesitate to offer the RX-A8A a substantial energy reserve by combining capacitors with a capacity of 22,000 microfarads on the transformer.

New chassis structure

However, using such a generously sized transformer entails certain mechanical constraints. Yamaha therefore had to redesign the chassis structure of the RX‑A8A. The transformer takes place at the front of the box, just behind its facade, and is framed by two groups of electronics corresponding to the eleven power stages. This arrangement reduces the distance separating them from the supply and, consequently, minimizes the impedance of the supply circuit. Mechanically, this arrangement also has the advantage of being able to give the RX‑A8A chassis an “H” structure by providing it with a central reinforcement plate. Finally, a fifth foot, using brass parts, housed under the transformer optimizes the flow of any vibrations (see photo below).

8K/60 compatibility

Finally, let's not forget that the RX‑A8A is intended to be an audio‑video amplifier and if it boasts exceptional characteristics for its audio sections, it has also aims to be among the elements with very high level video characteristics. If it is able to manage old format analog video signals, it is particularly well equipped to best manage the most current digital video streams. A particularly visible point at the level of its HDMI ports. Rare on this type of equipment, they are all HDMI 2.1 / HDCP 2.3 type and have a bandwidth of 24 gigabits per second. The RX‑A8A, not only capable of handling HDR10+, is therefore also compatible with both 4K/120Hz and 8K/60Hz streams.

HDMI 2.1 with A and/or B video signals

In this regard, Yamaha specifies that the RX‑V8A is capable of handling 8K/60B and 4K/120AB signals. To clarify the situation, be aware that the suffix B means "compressed" while the suffix A indicates support for an "uncompressed" signal. In this case, the RX‑V8A will therefore manage UHD 8K signals at 60 Hz compressed, and UHD 4K signals at 120 Hz compressed or uncompressed.

YPAO autocalibration

Finally, as is traditional with Yamaha, the RX‑V8A has the brand-specific YPAO autocalibration system via a supplied microphone. In addition to the phase and level adjustments, essential for the proper reproduction of enveloping sound environments, it also compensates for the acoustic imperfections of the speakers and the room to provide more natural reproduction.