@nawrocjp Something to keep in mind, we don't alter music equalization on Pandora from how it appears on the original releases, unlike terrestrial radio, which compresses the entire broadcast. As a result, some songs sound louder than others. However, we do use the Replay Gain technique that encodes a fixed volume adjustment into the mp3/mp4 header so that the actual player (web browser, phone or device) can adjust volume just as the track begins playing. If there are vast differences, it could also be due to different instrumentation or arrangements causing different apparent levels of volume where the actual decibel levels are the same.
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You mentioned using a built in sound mixer. Just to clarify, are you using the volume bar on the player while listening to Pandora?
Pandora has a separate volume control. Make sure it isn't all the way down, the volume control is located in the bottom right corner of the Pandora page. If that's not it, make sure you are plugged into the main speaker outputs of your sound card. Sometimes there are two outputs. Pandora may only play from one of them on machines with some sound drivers. Updated drivers have fixed this for many listeners. If on a Windows machine, make sure that the "Wave Balance" volume is set at least 50% on your advanced volume control window. This is accessible by double-clicking the speaker in the lower-right corner of your screen.
Hope this info is helpful.
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