Grand Integra
(1984 - 1992)

Very well remembered Mozilla-esque & Gargantua-esque heavyweight powerhouse which needs two people to be lifted : 63 kilos.

Able to output 2x 1,2kW at 1 Ohm, one might imagine this having been aimed at PA reinforcement for deaf audiences but, in fact, the circuit's engineering are very much fine-tuned and almost microscopic.

The secret inside lies in the two secondary transformers : these are "In Phase" transformers which echo the Signal In-Phase Filters of the Integra P-308 high-end preamplifier. In Phase transformers are to cope with the reactive load of loudspeakers, and not only their resistive aspect ; these transformers are to avoid the phase shift between voltage and current in the amp-to-speaker signal path.
Most pronounced around the speaker's resonance frequency, this phase-shift also happens between the voltage and the charging current in the amplifier's power supply ; these charging currents may start fluctuating along the low-frequencies contained in the musical signal. Out-of-phase charging currents can generate electromagnetic flux which in turn often induces voltages of the same incorrect phase in the nearby driver stage (through which the audio signal passes) ; the problem is then, naturally, sent to the loudspeaker... muddy bass and blurry soundstage.
Real Phase transformer are inserted between the positive and negative charging currents of the the power-supply and the capacitors : as the positive and negative currents pass through the transformer's two windings, unwanted peaks and dips cancel each other out - in phase ! You can see the schematic of the Real Phase system by clicking the "more" button below - click !

Otherwise, the Grand Integra M-510 is real dual-mono amplifier : two power cords and two toroidal power transformers ! A fifth and common trafo is used for the meters and out-of-the-signal-path circuitry such as speaker relays. Each channel benefits from two 33,000µF / 100V capacitors - for a 99,000µF total... Each channel's power board holds 7 pairs of (I believe Sanken) transistors, 28 in toto. Gargantua-esque indeed.
Linear Phase Switching is included for true waveform linearity (see the Integra P-308 page on TVK for details) and an elaborate complex protection circuitry kicks in if necessary - 1,2kW per channel can transform your fragile tweeters into live frisbees.

A cool "waiting monitor" flashes some leds geometrically while a dimmer allows to switch off the VU meters' lamps ; gold-plated terminals and solid wood sideburns give the ultimate in reliability and looks, respectively. Both the variable and direct inputs are single-ended, though. The front flap hides the speaker selector (A, B, A+B), variable input pots, dimmer, and meter range selector (x1 or x0,1).
The Onkyo Grand Integra M-510 was lavishly displayed in a "Big New Sound" section in Stereo Sound #73 (winter 1985), and was seen in many a japanese Onkyo ad, often accompanied by the
Grand Scepter GS-1 horn loudspeaker. However, this golden Grand Integra now remains... quite invisible.

Looks-wise a bit heavy-handed and tacky and not really discrete with its 27cm in height, but, hey - you can't be Gargantua and look like Minnie the Mouse !



This post was made possible thanks to Henrik who loaned a very informative USA Onkyo catalog ; my own japanese sources will follow for an update.

This is an old TVK page.

It will remain online until its new version is ready.

This old page may contain errors and approximations.

Visit the (beta test) of TVK v2 !