After going through the installation I thought the Denon sounded better than the Integra. Not only does the Denon sound clearer, it also seems to have a better sound stage. I thought it was all in my head, a placebo effect. Then last night my girlfriend commented that it "sounds crisper than the old one." The difference is noticable when watching movies (surround) or music (stereo).
I have only compared the AVR-X3400H with my old AVR-3805 and a pair of Azur-840E/Halo A21 in 2.0 and 2.1 using external DACs. I thought the Denon actually sounded slightly more transparent even in pure direct, but it wasn't a controlled test and I was sure it was "all in my head", though I would have thought Placebo should have worked the other way around.
With Audyssey on, it sounded even better, noticeable but no significant difference.
Does the newer AVR have that much better of chip set?
Different chip set for sure, but are theoretically limited by the weakest link, and that could be the volume control chips, as an example and as cited by Dr. Rich in the article linked below. According to him, to avoid that LSI volume control chip and other LSI chips, you would have to go pick the right integrated amps, certainly not the entry level ones made by companies that also make AVRs and AVPs. Interesting, his table happened to show several Onkyo/Integra models did use some presumably better SSI chips.
https://hometheaterhifi.com/technical/technical-reviews/options-by-supplier-and-price/
"A key takeaway: circuit quality in the direct mode (stereo or 7.1) is almost always invariant to AVR prices in the range of $400 to $2,000. As examples, the $250 Yamaha RX-V367 and Marantz AV8801 ($3000) use the same Renesas LSI chip (R2A15220FP). With the LSI analog chip in these products, the sound of the direct mode is relatively constant, although a more robust power supplies, addition a quality output buffer and enhanced DC blocking capacitor quality can make small differences.
Unfortunately it is not possible to actually do this listening test just proposed in practice because the Yamaha RX-V367, like almost all low cost AVRS produced today, does not have preamp outputs. The experiment would be possible using the older RX-V665 ($550)"
In that article, he claimed (not quite true according my research on the topic)that:
"Even a low-cost stereo integrated amplifier will offer better performance in its analog input to its preamp output than an AVR in direct mode, since stereo products are made from SSI chips and, occasionally, relays. Value-priced stereo preamps with exceptional internal parts quality, including the electronic volume control chip, such as the Emotiva XSP-1 recently reviewed in Secrets (link shown below),will reveal any coloration of the LSI chip in the AVRs in direct mode."
According to what I could see in a few service manuals I downloaded for several integrated amps and AVRs, many "cheap stereo integrated amps, such as Yamaha's A-S801 and lower models also used similar ICs found in their AVRs. If I may borrow the term originated by @ADTG, those seem to be AVR based integrated amps.
I believe he's right about the sound being "relatively constant" among AVRs/AVPs, but I definitely don't believe the so called cheap integrated amps, or even expensive ones, can reveal "any coloration of the LSI chip in the AVRs in direct mode" as such. The LSI chips he referred to, are getting better, and I don't think they are the bottleneck any more. In fact, I would trust those ICs more so than custom designed analog circuits that you have to rely on the competence and attitude of the designers.
