Upon review of the Chassis designs, both the 9000ES and the DA4ES have something special to offer.
Sony TA-9000ES Chassis
Once again, Sony went out of their way to “dot their I’s” on the 9000ES to assure that the chassis is shielded and isolated vibration and other potential external and internal noise elements. For example, non-conducting strips are bonded along the perimeter of the chassis to isolate it from the cover. This makes the cover completely sound dead when vibrated. The tell-tail sign this works is when you flick the cover and it doesn't ring, but instead, is quickly muffled. The reason behind this addition is simple. In certain Home Theater environments, it is possible for the sound of a movie/music, especially with bass, to cause components to vibrate and create an annoying sound when listening to a sound track. This is especially true of furniture and TV cabinets. By making the cover of the 9000ES sound dead, it is one component in a Home Theater rack that you can be assured will not vibrate.
Other quality refinements include copper strips located on each sides of the front plate to assure it is properly grounded to the chassis. This is likely done to help reduce/eliminate any grounding cross talk that may occur between the digital panel and the processor.
In an effort to reduce noise and cross talk, additional internal features help isolate key internal assemblies. For example, there is a non-conductive aluminum plate down the entire length of the chassis that is likely added to help isolate the power supply from the processing boards. It would have been more effective in this role however, if the plate was solid and did not have cutouts where EMI can leak through. In addition to this plate, the main DSP board is isolated from the analog pre-amp boards with thick, non-conductive film. Furthermore, the analog board has 10 Transistors (2 per channel in a push-pull configuration), each mounted to oversized S-Fin heat sinks. These units can be seen at the very front of the Processor, located just behind the front panel.
“S-Fin” is a term used to describe a series of ribs running the length of each fin of the heat sink, staggered incrementally in the shape of an ‘S.’ This is done to prevent the fins from cumulatively adding resonant frequency vibrations to the boards. Each staggered rib creates a unique harmonic frequency for a specific fin, which is dependent on its location. The net result is that no two fins are alike, and therefore, cannot resonate at the same sound frequency and create unwanted noise.
Another interesting, yet simple feature added to this design is a thick putty material on the top of most of the IC’s. This is done to help damping vibration of the IC’s from external noise. It’s not an expensive addition, but it does continue with the overall theme of noise reduction that Sony has designed into this unit.
The entire internal design of the chassis, the location of key assemblies and their respective shielding, the size and build quality of the heat-sinks, and the added damping materials are all designed around isolation and noise reduction, thus assuring the cleanest, purist sound from this Processor.
Sony STR-DA4ES Chassis
The basic Frame-and-Beam design of the STR-DA4ES chassis is similar to that of the 9000ES, but it lacks most of the detailed isolation and grounding features.
Still, there are some redeeming qualities of the DA4ES chassis that are worth pointing out. Given this Receiver does contain amplifiers, unlike the 9000ES, Sony created what’s called a ‘Horizontally Opposed Chassis.’ For signal purity, left and right signal elements are apposed channel by channel on two separate, large S-Fin heat sinks that run down the length of the unit. Sony also optimizes their layout in this large chassis by mounting the DSP and Analog boards on the side and rear of the unit. In addition, they cleverly located the power op amps in the middle of the unit and use the long length of the aluminum fins on the heat sinks as basic shielding for the processing boards. This technique is somewhat effective, but does not exhibit near the level of isolation as what’s designed into the 9000ES.
Some of the refinements found in the TAE-9000ES are not included in the STR-DA4ES. For example, the chassis cover of the 4ES is not dampened. Again, in certain Home Theater setups, it is possible to get a ringing noise from components when the frequency of the audio sound matches the harmonic frequency of that chassis. The 9000ES eliminates the possibility of vibration noise by dampening the cover.
In addition, there is no damping foam on the IC’s, and the electronics are missing the non-conductive film that helps isolate the boards from one another.