Was made between 1984 to 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 !
Sadly all the links are dead in this article and obviously I didn't write this as I got lost at; "these are "In Phase" transformers which echo the Signal In-Phase Filters "
No idea what he's talking about and to be honest I'm only interested in the VU meters and how they will look in my room with black walls and black carpet and a glass of red in my hand.
*My mate's one was one of the duds manufactured in the Japanese Year of the Dog when a newly returned engineer from East Germany got caught up in the euphoria of the Berlin wall coming down and they built some really gruddy cheap ones for the mass market, for dummies basically and he being newly awaken to the wide world misinterpreted the Year of The Dog as The Year of the Dud.
Postage and a few dollars plus a bottle of 12 year old Metaxa should clinch the deal I think.
** Bait tossed out...waiting....