ONKYO Integra A-927 (1997) | The Sound-ism Integra

The Onkyo Integra A-927 is a sophisticated integrated amplifier that combines substantial power reserves with advanced circuit design and extensive sound customization. Originally priced at ¥95,000 (before tax) this 18 kg Japanese amplifier stands out for its non-feedback power amplifier, double-core laser transformer, and unusually flexible tone controls designed to adapt its sound to different listening environments.

Onkyo Integra A-927 – Main Specifications

Rated output power: 160 W + 160 W (4ohm, 20 Hz–20 kHz); 100 W + 100 W (8 Ω)

Dynamic power: 335 W + 335 W (2 Ω, 1kHz); 225 W + 225 W (4 Ω); 170 W + 170 W (6 Ω)

Total harmonic distortion: 0.04% at rated output, 8 Ω

Intermodulation distortion: 0.04% at rated output

Damping factor: 150 (8 Ω, 20 Hz–20 kHz)

Signal-to-noise ratio: 105 dB (CD/Tuner/Line/Tape); 117 dB (Direct/Power Amp Direct)

Phono compatibility: MM and MC cartridges

Dimensions: 445 × 165 × 434 mm (W × H × D)

Weight: 18.0 kg

Original suggested retail price: ¥95,000 (excluding tax)

Proprietary Technology and Design Features: Non-Feedback Power Amplifier - Direct Control and Fast Response. Non-feedback amplification is one of the defining technologies of the Onkyo Integra A-927. While conventional amplifier designs commonly use negative feedback (NFB) to improve measured performance and stabilize circuit operation, Onkyo pursued a different approach for its power amplifier stage. The company argued that negative feedback can allow a speaker's back electromotive force to influence the amplifier through the feedback loop. Its non-feedback design aims to avoid this interaction, prioritizing the amplifier's inherent electrical characteristics. The intended benefits include fast response, strong speaker-driving capability, effective control over speaker movement, and a wide dynamic range. From delicate musical details to demanding high-power passages, the design was intended to preserve clarity and dynamic expression. Double-Core Laser Transformer - Stable Power Delivery. The double-core laser transformer was engineered to supply the amplifier with substantial, stable electrical power while minimizing magnetic leakage that could interfere with sensitive audio circuitry. Onkyo combined two coil-shaped cores with low magnetic resistance, an extra-thick copper-wire winding, and an internal magnetic structure. This arrangement was designed to deliver high current when the music demanded sudden changes in power. The goal was straightforward: a robust power supply capable of responding to dynamic musical peaks without allowing unwanted magnetic interference to compromise the signal. 

Quality components and mechanical rigidity are central to the A-927's construction. Its specification includes WIMA film capacitors from Germany, specially selected blue capacitors, a 70-micron-thick copper-foil printed circuit board, and a four-gang die-cast volume control. The amplifier also features a thick aluminum front panel, an MDF top cover, and a box-style chassis structure intended to provide a solid mechanical foundation. An extra-thick power cable with a polarity indicator completes a design that pays attention to both electrical performance and practical installation. Three selectable operating modes allow the A-927 to adapt to different listening preferences and system configurations. POWER AMP: The dedicated POWER AMP DIRECT input feeds the power amplifier through its dedicated volume control, allowing the unit to function as a power amplifier for a compatible external preamplifier or processor. SOURCE: Bypasses the tone-control circuit for users who prefer a more direct signal path. TONE: Engages the tone-control circuitry for those who want to adjust the sound to their room, speakers, or musical preferences. This flexibility makes the A-927 more than a conventional integrated amplifier. It can also accommodate a range of system configurations without sacrificing its built-in functionality. Mid-Bass Presence control is one of the A-927's more distinctive features. Onkyo identified the 200–300 Hz region as an area where typical Japanese listening rooms could develop excessive or uneven mid-bass energy. The amplifier provides a switchable center frequency in this range, allowing the listener to adjust the energy around the upper-bass and lower-midrange region. One particularly useful application is to boost the main BASS control while using Mid-Bass Presence to reduce the resulting excess in the mid-bass. This makes it possible to emphasize deeper bass without allowing the upper bass to become unnecessarily heavy. Comprehensive tonal adjustment gives the A-927 considerable flexibility for room matching and personal preferences. Its controls include a bass adjustment with up to +14 dB of variable boost, independent left- and right-channel treble controls, and a stepped balance control. A subsonic filter helps reduce unwanted very-low-frequency signals, while a muting circuit provides convenient operation. For vinyl enthusiasts, the integrated MM/MC-compatible phono equalizer supports both moving-magnet and moving-coil cartridges, avoiding the need for a separate phono stage in many systems. The inclusion of three tape connections also makes the amplifier attractive to enthusiasts who enjoy recording, dubbing, and integrating multiple vintage or contemporary source components.

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ONKYO Integra C-729 (1998) | Precision and Purity

Released around 1998, the ONKYO Integra C-729 (Onkyo DX-7911) was a high-end CD player designed to extract musical information with exceptional precision. Priced at ¥120,000 in Japan, it combined sophisticated digital conversion, carefully engineered power supplies, and a vibration-resistant disc mechanism in a substantial 10.2 kg chassis.

ONKYO Integra C-729 – Main Specifications

Original price: ¥120,000 Japan, 1.800 DM Germany

Frequency response: 5 Hz–20 kHz

Harmonic distortion: 0.0025% or less

Dynamic range: More than 100 dB

Signal-to-noise ratio: 110 dB or more

Channel separation: More than 100 dB

Wow and flutter: Below the measurement limit

Analog output level: 2 Vrms

Laser pickup: 3-beam semiconductor laser

Digital-to-analog conversion: Dual single-bit DACs with fourth-order noise shaping

Dimensions: 445 × 131 × 365 mm (W × H × D)

Weight: 10.2 kg

Included accessory: Wireless remote control

Advanced Digital Technology and Precision Engineering - Sampling Rate Conversion for Improved Digital Filtering. Sampling rate conversion: One of the C-729's distinctive features is its conversion of the CD's original 44.1 kHz sampling frequency to 52 kHz. According to ONKYO's design approach, this conversion makes noise reduction easier by simplifying the digital filter circuit. It also helps avoid the effects of jitter associated with the conversion process, contributing to improved conversion accuracy. Digital-to-analog conversion: The C-729 employs two single-bit DACs, each using fourth-order noise shaping, with independent conversion paths for the left and right channels. Differential operation helps suppress distortion, while the noise-shaping system is designed to reduce in-band noise associated with single-bit conversion. The result is a carefully engineered approach to translating digital audio into an analog signal. Premium components: ONKYO paid particular attention to the circuitry following the DACs, incorporating film capacitors from German manufacturers Raederstein and WIMA. These components form part of the analog output circuitry, where component selection and circuit layout are important considerations in maintaining signal integrity. Disc-reading accuracy: The C-729 features a digital servo system that measures errors caused by disc eccentricity or warping whenever a disc is loaded. It automatically optimizes tracking and focus, including their respective offsets and gain settings. This helps the player compensate for variations in disc condition and mechanism alignment, reducing reading errors. Mechanical precision: The three-beam laser pickup is driven by ONKYO's original linear motor mechanism, designed to provide responsive operation and high-speed track access. A newly developed rubber magnet improves vibration damping in the magnetic circuit. The die-cast aluminum tray, finished with a mat-like coating, further helps control unwanted vibration. Electromagnetic shielding: The complete disc mechanism is enclosed in a steel case to reduce the influence of electromagnetic noise generated by the pickup. Together, these measures reflect the attention given to both mechanical stability and electrical interference. Stable power delivery: The C-729 uses a double-core laser transformer, a type also employed in ONKYO Integra integrated amplifiers. Its design helps reduce unwanted magnetic leakage. The audio circuitry receives power from two 10,000 µF smoothing capacitors. ONKYO also employs two-stage voltage regulation for the analog section and three-stage regulation for the DAC circuitry, aiming to provide stable operating conditions for both sections. Vibration isolation: DuPont Corian insulators provide another element of the player's mechanical design, complementing the damping measures incorporated into the disc mechanism. 

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MB Quart Reference (1985) | Legendary Active Loudspeaker

Some loudspeakers are designed to reproduce music. Others are built to make the listening experience an event in itself. The MB Quart Reference belongs to the latter category, combining imposing physical dimensions, sophisticated active amplification, and an ambitious four-way design to deliver a truly full-scale musical presentation. Celebrated in the German hi-fi press during the 1980s, this remarkable loudspeaker embodied the pursuit of uncompromising sound quality, backed by an impressive set of technical specifications and a prestigious stereoplay test verdict in June 1985.

MB Quart Reference: Main Specifications

Type: Four-way active loudspeaker system

Frequency response: 16–32,000 Hz

Total available amplifier power: 500 watts

Amplifier performance

Bass amplifier signal-to-noise ratio: Greater than 80 dB, typically 85 dB

Midrange/high-frequency amplifier signal-to-noise ratio: Greater than 90 dB, typically 98 dB

Automatic activation: Selectable switch-on thresholds

Automatic standby: Approximately four-minute switch-off delay, with a tolerance of ±1 minute

Loudspeaker drivers

Tweeter: 25 mm MCD titanium dome

Midrange: 50 mm MCD dome

Mid-bass: 245 mm cone driver

Woofer: 380 mm cone driver with cast chassis

Cabinet finish: Real mahogany wood, with other finishes available at additional cost

Grille: Removable textile grille

Dimensions (W × H × D): 53 × 187 × 53 cm

Weight: 134 kg per loudspeaker

The Technology Behind the MB Quart Reference - Four-Way Active Design. Active loudspeaker architecture is one of the defining characteristics of the MB Quart Reference. Rather than relying on a single external amplifier and a conventional passive crossover network, this system incorporates its own amplification, with separate amplification arrangements specified for the bass and midrange/high-frequency sections. The advantage of this approach is greater control over the different frequency ranges. It also allows the loudspeaker system to be designed as an integrated whole, with its drivers and amplifiers working together toward a common performance objective. With a claimed total available power of 500 watts, the Reference was clearly intended for listeners who wanted more than a compact, living-room hi-fi experience. A Four-Driver Array Covering the Entire Audible Spectrum. Specialized drivers handle different portions of the music, from deep bass to the highest treble. The substantial 380 mm woofer provides the physical foundation for low-frequency reproduction, while the 245 mm mid-bass driver handles the next section of the spectrum. Above them, the 50 mm MCD dome takes care of the midrange, where vocals and many of the instruments that define a recording's character reside. A 25 mm titanium-dome tweeter completes the arrangement, extending the system's claimed frequency response to 32 kHz. The result is a sophisticated driver configuration designed to combine scale, bandwidth, and detailed musical reproduction. MCD Dome Technology and Titanium High Frequencies. Dome-driver engineering is another notable feature of the MB Quart Reference. Both the midrange and tweeter use dome diaphragms, with the tweeter specifically identified as a titanium design. The midrange dome is intended to reproduce the critical frequencies responsible for vocal presence, instrumental texture, and much of the perceived naturalness of a recording. The titanium tweeter extends the response into the upper frequencies, helping complete the system's wide stated bandwidth. The original brochure identifies the midrange and tweeter as MCD dome units but does not fully explain the MCD abbreviation. It is therefore best to preserve the manufacturer's terminology rather than speculate about the exact material or construction involved. Amplifier specifications reveal how seriously MB Quart approached system integration. The published total harmonic distortion figure is below 0.006% at rated power, accompanied by an intermodulation distortion figure below 0.04%. The adjustable RCA inputs accommodate a range of source-output levels, with specified settings extending from 500 mV to 16 V. This flexibility would have helped the system integrate with different preamplifiers and other compatible audio sources. A selectable bass-level switch offers adjustments from +2 dB down to −8 dB, referenced to 30 Hz. This provides a degree of control over the low-frequency balance to suit the room and listening preferences. Automatic Operation for Everyday Convenience. Automatic power management makes this imposing loudspeaker more practical to operate. The Reference features selectable signal thresholds for automatic activation, allowing the system to respond to an incoming audio signal. If no further signal is detected, the loudspeaker switches off after approximately four minutes, with a stated tolerance of one minute either way. A Cabinet Designed to Make a Statement. Real mahogany construction gives the MB Quart Reference a suitably luxurious appearance. Measuring 187 cm tall, with a footprint of 53 × 53 cm, each loudspeaker has a presence that few contemporary domestic hi-fi speakers can match. At 134 kg per cabinet, these are exceptionally substantial pieces of equipment. The removable textile grille offers a more traditional furniture-like appearance, while the exposed driver arrangement presents a distinctly technical aesthetic when the grille is removed.

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