We've done some extensive testing on this and unable to reproduce. From logs, we can see that users on 0.8.8 are streaming on 320kbps, with the "High Quality Streaming" mode selected. From the files we tested, we also checked the backend and the actual files themselves, and they were also at 320kbps.
The only thing I can think that might be causing this is the "Set the same volume level for each track" setting. Try turning this on for 10 seconds, and you should notice a difference. Turn it off and it should return to normal.
Perhaps the level and quality drop is related to something else? It is impossible to get the 0dBFS output from Spotify 0.8.8 after restarting it. Can you tell me step by step what output level are you getting when trying to reproduce the bug using my instructions?
I can confirm that I have this exact same bug on v 0.8.8 on my Mac. Only realised this was a problem when trialing the web player, which sounded way louder and crispier than the native OSX app. Testing them both out, the OSX app is defientely quieter.
Ok, I followed your suggestion and here is what I did:
1. I opened Spotify 0.8.8 and my output level was at -4dBFS
2. I switched "Set the same volume level for each track" on and I kept it that way for more than 10 seconds
3. I switched "Set the same volume level for each track" off and after 2-3 seconds the level suddenly got back to 0dBFS (original value of most songs)
The problem is, after I restart Spotify, I get -4dBFS again...
As an aside, I might add that using Spotify to normalize the volume on all tracks results in a noticeable decrease in sound quality. Whatever mix of compression and limiting and what not that is being done... is not kind, is not transparent.
At least in the v0.8.5 client, you can turn off this "normalize volume" thing and it stays off.
This fixed the issue for me and makes sense to me on a technical level. Most likely when you normalize volumes across tracks ("Set the same volume...") the Spotify client runs the audio through a digital compressor/limiter. These have their place but they tend to kill sound quality if overly-applied.