Originally Posted by vourt
Thanks! will the Marantz SR7013 will have the same auto room speakers & sub setup similar to the high end models in Denon?
The only quantifiable and meaningful difference based on the physical design, when external amplifiers are not used, between the SR7013, and the X4500H, is that the SR7013 will cost more. I'm not shy about spending money, but it's hard to see the justification in this case. A similar situation exists with the SR8012 and X6500H, except that the SR8012 adds a toroidal power transformer.
If you can get the Denon AVR-X6500H for about the same price as the X4500H that's great. You'll get better power amplifier circuits with one amplifier channel per circuit board, the same used in the SR8012 and X8500H, relays instead of bi-polar transistor muting circuits, external multi-channel inputs, and a better power supply for the opamps. That decision would be easy.
The SR7013 and X4500H units use mostly the same circuit boards. The SR7013 adds the HDAM buffers. A similar situation exists for the X6500H and SR8012. The SR7013 and SR8012 HDAM buffers lack the sophisticated power supply, higher rail voltages and power filtering of the HDAM buffers in the AV7704 and AV8805.
In an application such as this one, where only the internal amplifiers in a Marantz AVR are used, the HDAM buffer for each channel adds an electronic stage between the volume control (identical in each unit) and the input to a power amplifier stage (identical in each unit). The volume control is perfectly capable of driving a power amplifier channel input stage on its own, based on the impedances involved and the output capabilities of the volume control. The HDAM is purely an analog electronic circuit that ideally has a flat frequency response and a gain of 0dB. An HDAM circuit replaces a direct connection between the volume control and amplifier input stage. The HDAM doesn't do some AI or other magic to improve the signal.
To explore this subject a bit, here is some information from a review of the Denon AVR-X3500H from the Audioholics website. The goal is only to explore the output capabilities of the volume control, not discuss the overall review.
This review of the Denon AVR-X3600H is interesting in that is has a graph about 1/2-way down the page (admittedly provided by Denon) that shows the output of the volume control of the X3600H, which is the same control used in the X4500H, plotted against THD+N. The measurement is likely (not specified by Denon) taken in a way that the volume control is only connected to the preamp output, which is a special case. In most all cases the volume control drives the preamp output and the input to the power amplifiers channel, which means that an external location on a unit is not available to take this pure measurement.
The volume control is driving a 10K ohm input impedance in the test gear, which is a tougher load than driving the power amplifier. The HDAM circuit appears to present a similar impedance to the volume control output as the power amplifier input stage, so there seems to be no advantage from the HDAM stage in the area of load on the volume control. The performance shown in the chart is quite good. Noise (which would be specific to the X3500H) dominates the measurement to over a 2V output. The HDAM circuits can do nothing magical to improve this performance.
Some facts, some opinions above. What did I miss or get wrong?