Onkyo TX-SR805 Design and Construction

The Onkyo TX-SR805 receiver is a larger receiver, at a height of 7 5/8” and weighing in at over 50 pounds, it is a bit heftier than many run of the mill midrange components. Actually, at its asking price, the TX-SR805 outweighs other competitive receivers by about 10 lbs, an increase of 125% over the typical weight.

The chassis is constructed of typical light gage steel but with a relatively thick-brushed aluminum faceplate, again by receiver standards, and is available in a black or a silver finish. The sample sent for the review was the black model.

The front panel is clean, with most of the controls tucked away behind an aluminum foldout door secured with the typical push type latch. The general appearance has been updated some in the last few years since the 602 was current. The recessed volume knob is backlit with a very nice cobalt blue that is adjustable as part of the front panel dimmer/off function. Unfortunately, the front text display does not use the same color, instead going with a bluish green that is an odd match.

Upon removing the top cover, we see that cover steel gage is slightly thicker than typical and that the chassis is still sturdy even without it. The sides of the chassis interior have full length, half height side panels that provide frame continuity to the front and back panels. The heat sink and front panel are connected with an additional full height frame also connected to the side panel, which provides additional rigidity for the weight of the transformer.

Inside, the Onkyo TX-SR805 is densely packed but very cleanly laid out, with a minimum of wire bundles strung across the inside of the chassis unlike some receivers that I have seen. The main power run is routed to the transformer along the left side panel, but other than a few other short wire runs and some short runs of computer styled ribbon cable there is very little in the way of cabling spaghetti. Short, clean internal cabling runs suggests a well thought out component arrangement where every circuit is near to where it is supposed to be in order to do its part along the chain. It suggests, to me, that perhaps this Onkyo receiver was a little more carefully designed than other competing products.

Centered at the front is a large EI core transformer that is separated from the rest of the circuitry by a full width machined aluminum heat sink. The main transformer is flanked by two light gage housings that mount 80 mm exhaust fans with vents at the front of each side panel.

Coupled to the back of the heat sink are seven discrete amplifier boards for the power output stage. Nestled in between the amplifier boards is a pair of decent sized main power supply capacitors.

The back third of the housing is occupied by the input, output, and processing circuit boards. These boards consist of a discrete digital a/v board at the HDMI inputs, a digital audio board at the coax/toslink inputs, a shielded board for the radio inputs, an analog a/v input board with a supplementary aluminum heat sink, and power supply input boards at the left.

The power amplifier design of the TX-SR805 is a discrete dual push-pull configuration for which Onkyo received THX Ultra2 certification. Amplifier distortion is controlled with a three stage inverted Darlington circuit and the TX-SR805 boasts a 110 dB S/N ratio at full power. Onkyo claims the amplifier section is rated to drive 4 ohm speaker loads and is said to be capable of 60 amps of instantaneous current.

As I have said previously, the power supply of the TX-SR805 is unusually beefy for this price range and there is no other receiver on the market near this price that features a THX Ultra2 certified amplifier section. The power feed is supplied at the rear left corner and is protected by a main power supply fuse that is rated 12A at 125V, allowing a maximum outlet draw of P = 12A x 125V = 1500W. The seven amplified channels of the TX-SR805 are rated to output 130W each providing a potential momentary output total of 910W. The aforementioned main power supply capacitors are of Onkyo manufacture with 2 x 15000F at 71V that allows plenty of headroom for the rail voltage.