My old JVC 8010 finally bit the dust so I decided to do some research and get a good receiver to match the quality of my Polk Monitor 10B's.
When I tried the V485, it was my first Yamaha, and I LOVED the sound quality out of the box when playing music - it was so clear and had a lot of image. I was sold!
Note: I had the YPAO's EQ disabled (set to "Through"), so everything was flat with bass/treb disabled and set to 2-channel stereo. Ext Bass was off, but the Sound Enhancer was ON. And I used 192k WMA music files.
The only problem I had was that the bass in a lot of songs seemed to howl a bit. So, I did some research and found out this was due to a standing wave in my listening room. So, I downloaded the android spectrum analyzer app "Spectroid" and could see a huge spike at 49Hz when I heard the howling. Unfortunately the 485's EQ can't create a good notch filter because each band has a wide Q factor, but I noticed the V685 has an advanced EQ in that you can create a real-narrow Q factor and can also adjust the center frequency. So, I exchanged the 485 for the 685 and I was able to setup a 49.5Hz notch filter and the standing wave was gone!
Now I was enjoying really good sound quality, especially with the sound enhancer ON with my WMA music files and Bluetooth. As a previous member said in this forum, it put a smile on my face every time I would listen to music.
But, then I noticed a firmware 1.41 update (out of the box my receiver was v1.31), so I flashed the newer 1.41, and boy what a mistake. The "sibilance" (high end "hiss" as when singer says "S"s) was harsh and I hated it - it downgraded the listening enjoyment to a point that it actually got me in a bad mood. Also note that I still had everything flat (YPA0's eq off/Through). So it wasn't a EQ or treble setting that was causing this harshness at the high end - the settings were the same as when I have 1.31.
Basically, every time a singer would sing a word with an "S" in it, it just sounded harsh
Whereas with the v1.31, the "s"s were just clear and smooth.
So, I called Yamaha up and they said they never heard of this problem before. Keep in mind, I am far from a real audiophile, so my 50+ old ears are nothing special. But I could hear the difference pretty easily with certain songs, like Bebe Rexha's "I'm A Mess".
So, after a few calls, a support tech was able to locate the v1.31 firmware file and sent it to me. I was able to flash down to it with no problems using a USB stick, and yup the sound quality returned to being excellent. As a test to make sure something didn't happen when I did the 1.41 update, I flashed back up to the 1.41 and the harshness returned. I flashed back to the 1.31 and its back to sounding great.
The curious thing is that the 1.31 firmware file is 92k in size, and both the 1.41 and 1.47 are only 42k in size - thanks a huge reduction. So I don't know exactly what changed, maybe they changed the algorithm for the sound enhancer, who knows, but I just hated the sound quality of the later firmware versions.
So, I just wanted to express my findings and if you do have a version higher then 1.31, you may want to try as a test to downgrade to 1.31 and see if you can notice the sound quality of music take a significant step-up in clearness and smoothness. And if you do, maybe if more of us report this to Yamaha, they will fix the cause because right now I'm stuck at version 1.31 - I can't get future fixes or new features like the Bluetooth output without sacrificing the sound quality.
And if anyone upgrades to 1.41 or 1.47 (from 1.31) and notices the high-end seems harsher, it's not your imagination - the upgrade somehow downgrades the audio quality (at least to me).
1) When Yamaha sent me the 1.31 firmware file it was named "V685-0131.BIN", but make sure you rename it to "000402-0131.BIN" so the receiver will properly "see" it on the USB stick. Please don't ask me for the file, you should get it from the trusted source: Yamaha
2) Flashing up or down was extremely easy and safe - I didn't even loose any of the receiver settings after flashing in either direction. So you really have nothing to loose trying 1.31. Yamaha did a good job with their flashing feature.