Q: Why do so many audio fans prefer a vintage receiver over new receivers with modern technology? Are there reasons that older equipment can sound different or better?
I have a Technics SA-600 stereo receiver from the late 1970s. I purchased a new Denon surround-sound receiver thinking it would be an improvement, but I didn't like it. It was way too complicated to use, and even though the Denon supposedly had more power, music didn't sound as enjoyable as with the Technics. I used the same turntable, CD player and speakers for the comparison.
A: When it comes to receivers and amplifiers, older can be better.
The amplifier sections in new receivers often don't have the power and electrical current capability of vintage models, especially going from a stereo receiver to a surround-sound receiver the way you did. The manufacturers save money by cutting quality in the receivers' amplifier sections, then use the savings to add new features, such as extra channels for more speakers, Bluetooth, etc.
The power ratings in new gear are often inflated, as well. In real-world use, your Technics actually might deliver more power to the speakers, despite the Denon's higher advertised power rating. In addition, many receivers digitally process everything, including the volume control. Some people feel that this digital processing degrades the sound.
There also is the possibility that the Technics' power is not as "clean" as the Denon's and produces more distortion. This might sound counterintuitive, but many listeners think that mild distortion lends a pleasant quality to the music. That is the reason lots of people prefer tube amplifiers and vintage speakers even though the old equipment might not reproduce the music as accurately as modern gear.
In general, though, I think if that if you choose carefully, you can get better sound with modern equipment than with vintage. You just have to be careful about what you buy and how you match components together. There is good stuff and bad stuff littering every price point.
You can get much more speaker for your dollar than you could years ago. And most modern turntables will sound better, too, but much of that might be by virtue of their newness. Old turntables can have a worn platter and tonearm bearings that degrade the sound.