got a question for the experienced folks.
Would there be any significant differance from my X4300H with RCAs to an external amp verse a X3700H/X4700H to the same external amp using the “new” Denon pre out mode?
I have experience with similar models and I can offer some comments based on specs, measurements and subjective impression as follow:
In direct and pure direct mode, if you don't need the output voltage to exceed about 1.4 to 1.5 V. There is no evidence to even speculate because the main contributing factors to SQ including circuitry, dac, volume control and opamp ICs are practically the same. With dsp it depends.
If you need more than 1.5 V, then the answer would be, it depends. At output voltages higher than that, THD+N would starts to increase quickly, due to feedback from the power amp section (that would start to clip), and the 4700 is immune to that if preamp mode it used.
Even then, I say it still depends because:
a) Without preamp mode, based on measurements of the 3300 (Audioholics) and the 4700, 3700 (Audiosciencereview), the Denon AVRs THD+N would increase from the power amp's clipping point (about 1.5 V) but would still be at about 0.018%. That's based on a 1 kHz test signal, but the test results showed even for the 20 to 20,000 Hz range, THD+N remained below 0.032%.
b) Depending on your distance, max dpl you listen to at the distance, your speaker's sensitivity and your power amp's gain, you may not ever need more than 1.2 to 1.5 V anyway. For example, if my case, even 0.5 V is plenty high for me so my X4400H would likely have distortions of less than 0.001% for the most part.
In case you may ask how it would compare with using a Marantz prepro (so called separates):
c) Preamp mode or not, it could well be anecdotal if you consider the fact that the so called separates often have higher distortions. My favorite example is the Marantz AV7705 and 7706 that have slightly higher distortions than Denon's AVR-X3700H and X4700H, yet their owners seem to like them and never complain about hearing distortions and/or noise.
d) I highly doubt people can hear the difference between 0.001% THD and 0.05%, or even 0.1%. You can look at blind test results and will see that even experienced audiophiles, reviews could not score better than even 1%. So imo, the chance of audible difference between Denon AVR's normal mode, preamp mode and Marantz prepro would be 0, if compared following DBT or even just SBT protocols. Preamp mode will obviously save energy, help the unit to run slightly cooler, and prepros have the added benefits (no audible effects in most cases) of using XLR output.
My suggestion is, keep the X4300H and wait for the supply chain issues to get resolved (no idea when the way things are going) and see what's going to happen with the X4800H (or 4900?). Unless you badly need some features that the 4300 does not have.