The receiver includes the most popular decoding formats for movies and music, such as Dolby Digital EX, Pro Logic IIx, DTS-ES discrete, DTS 96/24 and Neo:6 and a few proprietary Onkyo digital signal processing modes, one named UNPLUGGED, which synthesizes surround sound from a stereo signal. I listened to most of the DSP modes and they all sounded natural without the artificial, exaggerated soundfields produced by some DSP processors. In fact, UNPLUGGED sounded very good, and created the equivalent of a discrete multichannel mix from a stereo input.
The TX-SR503 does have its limits. When pushed to higher volume levels, it tended to be rather strident and somewhat harsh. The higher levels were obviously straining the power supply. The receiver also got very warm—too hot to touch. Granted, the volume was set considerably higher than for normal listening levels, but sometimes I like it loud.
The AM/FM tuner performed very well in the TX-SR503. I live in a rural area, far from broadcast antennas and radio reception can be difficult, but the receiver pulled in stations from quite a distance using only the supplied antennas.
I compared the composite and SVideo output quality of the DVD player connected directly to the display with the video quality when connected through the receiver's video circuitry, and the receiver accurately passed a video signal with no noticeable artifacts. The receiver also incorporates component video switching features, which I did not evaluate.
The build quality of the TX-SR503 is better than some receivers in the same price range. A typical cost-cutting measure is to use a plastic or composite material for the front panel, which is not resistant to RFI (or Radio Frequency Interference, which is basically electronic noise from external sources). The Onkyo front panel is made of aluminum, which helps to shield the component from RFI.
Don't look for a lot of extra features on the TX-SR503, such as on-screen display, Auto EQ setup, video up-conversion or multi-room/multi-source operation (although it does have SPEAKER A/B connections). If these are important to you, check out another model. The Onkyo engineers emphasized audio performance, not features, when they designed this model. The Onkyo remote control is easy to use and intuitive, with functions that are simple to understand without having to read the owner's manual (which, incidentally is well written). The Onkyo TX-SR503 was very easy to set up. There are four menus for audio and system adjustments that are easy to understand and set. The receiver does not have an on-screen display, so all adjustments must be made while viewing the front panel display. Setting speaker levels was also simple because the TEST TONE button is on the remote control, not buried in a menu. The receiver's speaker output jacks are color-coded for easy connection and a sheet of colored labels is included to label the speaker wires. The back panel is well organized and simple to understand, and the Onkyo comes with a QUICK START guide to assist in basic set-up and operation.
Gordon Moore was right. Consumer electronics have dramatically improved and have become more affordable than ever, partially because of the exceptional progress in semiconductor manufacturing. I'm sure you didn't need me to tell you this, but the Onkyo TX-SR503 is a good example of Moore's law. Many parts of an A/V receiver have benefited from the advances in semiconductor electronics, not just the decoders or digital to analog converters. Volume controls, source selectors, and system controls are all controlled by sophisticated microprocessors.
The Onkyo TX-SR503 is a good basic receiver not laden with frills or fancy features, just good fundamental audio performance. The Onkyo TXSR503 will not win the "Best Features" award, but in my opinion its capabilities as a tuner/amplifier outweigh these shortcomings. It's certainly not a powerhouse, but it's an easy receiver to listen to for long periods with no listening fatigue. Its warm-sounding midrange and clean highs make it easy to enjoy. You'll want to use a subwoofer to fill in the low bass and let the receiver handle frequencies above approximately 80-100Hz. I would consider the Onkyo TX-SR503 as a great choice as the centerpiece for an entrylevel home theater system, no doubt outperforming a typical all-in-one home-theater-in-a-box, or as a second zone receiver for a multi-room system.