Dedicated audio engineering brings you the A-9555

Digital amplification enables significant power efficiency savings and supports smaller, more compact designs — obvious benefits for today's home lifestyles. However, Onkyo believes that these benefits should not come at the expense of the most important consideration: sound quality. With the A-9555 integrated digital amplifier, sound quality takes precedence over all else. By using Onkyo's exclusive Vector Linear (VL) Digital technology to remove any spike noise before it introduces errors into the inversion timing, it is possible to get a highly accurate analog-to-digital conversion. Also, at the heart of the A-9555 is a Pure Stream Power Supply — essentially a large power transformer — that ensures that you always have the on-demand power for the clarity and detail of a range of musical genres. By integrating the fundamentals of audio amplification with the potential of digital amplification, the A-9555 is a revelation in superior audio reproduction.

Vector Linear technology in a nutshell

PWM (Pulse Width Modulation) is the most commonly method of amplifying audio signals, thereby resulting in accurate analog-to-digital conversion. However, a digital amplifier generates a lot of "noise spikes" from sources external to the modulator circuitry. This spike noise introduces errors into the inversion timing, making accurate conversion into pulse widths impossible. Onkyo's response is a highly accurate analog-to-digital conversion circuit — VL Digital — that is unaffected by noise in the analog signal. Onkyo's VL Digital technology comprises a vector generator, an integrator (like a charger) and an inversion trigger generator. When the analog input signal is received, the vector generator outputs a current proportional to the size of the analog input. This current is sent to the integrator, where it is "charged." When the charge quantity reaches a specified value, the trigger operates and inverts the output pulse. Circuits charge and invert alternately, performing pulse width modulation proportional to the analog signal.

The upper and lower portions of the spike noise waveform are symmetrical, so they have the same area. Therefore, if the analog signal contains spike noise, their charge quantities will cancel each other out. This will ensure accurate pulse width modulation at all times. Onkyo's third-generation VL Digital technology includes an inverted Darlington circuit that goes beyond earlier versions to accurately produce a current flow based on the input voltage.

Optimum gain volume circuitry

Conventional volume attenuation methods must initially drop a signal close to the noise floor at low volumes. Even though the signal is only tainted with a little noise, the amount increases when the signal is amplified. Onkyo's Optimum Gain Volume Circuitry adjusts the gain so that less than half the amount of attenuation is necessary. This signal never comes close to the noise floor, and thereby eliminates the possibility of noise contamination that plagues conventional volume-attenuation designs.

Pure Stream power supply

Even though digital amplifiers are far more efficient than analog amplifiers, Onkyo's primary objective is to produce a sound that we can actually "feel," not merely hear. For that very purpose, the A-9555 includes a large-capacity transformer for the lowest possible impedance and superior transient response. Even though digital amplifiers are not susceptible to power supply voltage fluctuations, power supply performance requirements are as equally as demanding as analog amplifiers. You will find few other digital amplifiers grounded in this concept.

Discrete phono equalizer

In typical phono equalizers used up to now, the NF-type (negative feedback) has been most widely used. With this method, as more negative feedback is applied at higher frequencies, transient response deteriorates and the sound quality suffers as a result. However, the NF-type enables a higher signal-to-noise ratio and a wider dynamic range. With a less commonly used phono equalizer, the CR-type, it is possible to get an excellent transient response. With the A-9555's onboard phono equalizer, it is possible to keep negative feedback uniform over the whole frequency range. The A-9555's phono equalizer combines the benefits of both the NF-type and CR-type phono equalizers— a high signal-to-noise ratio, a wider dynamic range and excellent transient response — to produce exceptional sound quality.

Thick, low-impedance copper bus bars for perfect grounding

Electricity stored in an amplifier's condenser is outputted via an electric power line.To provide continuous output at full-power, a digital amplifier requires a large, stable flow of current. Any loss of power at the output stage becomes a hindrance to the instantaneous flow of that current. That's why Onkyo uses thick copper bus bars on the A-9555, to achieve an extremely low level of impedance. Printed circuit boards, by contrast, typically use beaten copper for their power lines. Because this beaten copper is extremely thin, it creates far more impedance. Even if it were the same width as the copper bus bars, a printed circuit board would yield much more impedance. So, if you want rock-solid power output at virtually any volume, the A-9555 won't let you down.

Comparison Specifications

• 2 x 85W per channel (8 ohms, 1kHz, 2 channels driven, FTC) / 200W/channel dynamic power (4 ohms, 1kHz, 2 channels driven, FTC)
• VL (Vector Linear) digital technology
• Separate transformers for L/R channels
• Banana plug-compatible transparent speaker posts, speaker A/B drive
• 6 audio inputs and 2 outputs, audio input/output, phono input, headphone jack
• Low-impedance thick bus plates
• Tone control (bass/treble On/Off)
• Balance control (L/R), discrete phono equalizer circuitry
• Pure direct mode
• RI-compatible remote control, compatible with RI dock for the iPod

Additional Specifications

• Hi-rigidity, anti-resonant chassis
• Heavy-duty inlet power cord
• Damping factor: 25 (front, 1 kHz, 8 ohms)
• Phono MM: 2.4mV/47 k-ohms
• LINE: 200 mV/33 k-ohms
• Phono overload: 60 mV (MM, 1kHz, 0.5%)
• Frequency response: 10Hz-60kHz (+1, -3dB, CD)
• Signal-to-noise ratio: 100dB (CD, IHF-A), 70 dB (Phono, IHF-A)
• Speaker impedance: 2 ohms-16 ohms

Manufacturer Specifications

• Aluminum volume and selector knobs
• Precision motor-driven volume control
• Power supply: AC 120 V, 60 Hz
• Power consumption: 110 W / 0.3W standby

Dimensional Specifications

• Dimensions: 17.06" W x 5.06" H x 16.94" D
• Weight: 28.7 lbs

Onkyo A-9555 Warranty Details

2 Year parts and labor

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