Fiio E7 Bass Clipping.
 

I recently purchased a Fiio E7 (which I'm using as a USB DAC/Amp) and am having this issue with the bass boost at all settings other than "0," which is "off." I've read many reviews that say that the E7's bass boost doesn't distort, though it didn't take me long to notice it during normal music listening, so I'm wondering if mine is defective. To make sure I was truly hearing added distortion, I found this site, and made a 50 Hz, 0 dBFS, 44.1 KHz sine wave. It sounds normal with the E7 set to "0," but all other settings obviously clip it, turning it into more of a "buzz" sound than a mellow "hum."

Further testing at setting "1" with a few different frequencies and levels revealed clipping points that align pretty closely with NwAvGuy's measurement of the setting "1" curve in his review, which makes me lean toward it being a design flaw rather than a defect (by which I mean that, for the sake of maximum output, Fiio just let the bass distort instead of creating some headroom to compensate).

Can anyone here with an E7 confirm this with their unit? If you try this, remember to turn your E7's volume down!

Yeah, looking at nwavguy's test results, its definitely pushing up the bass without adding headroom, so you'll probably want to apply some preamp if you use it as a DAC.

That said, if you're using it as a DAC I don't see why you'd bother with the bass boost when you could easily use a real EQ on the PC.

I can use Windows 7's built-in bass boost, which compensates to prevent distortion, but I still want a defect-free product. If the bass clipping is due to design rather than defect, then I'll be okay with simply not using it.

Fiio, via E-mail correspondence with me, has confirmed that this bass clipping is normal for the E7.