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Knocking/popping noise from Left Channel of 1ET400A from VTV

Dec 20, 2022
I recently purchased a used Purifi 1ET400A built by VTV (Hypex buffer, build date March 22). Everything was fine for the first couple weeks, then my left speaker began making a persistent knocking/popping noise, rhythmic in nature and almost like a fast metronome. The volume of the noise varies from barely audible unless your ear is to the speaker, to distracting at any modest volume of music. The volume of the noise is completely independent from amplifier output/music volume. It makes it as long as the amp is powered on. I’ve confirmed it’s the amps left channel causing the noise.

A visual inspection of the amps interior doesn’t reveal any obvious issue. I measured the current for each channel at the terminal, and the right reads 1.0 mA and the left reads 0.7 mA (I think. I also have no idea if that’s significant but I had a multimeter lying around so I did some prodding).

Any idea what it could be or what I could try? I know VTV offers a two year warranty on the build, but I’m not sure if this is a build issue or if the warranty even transfers to new owners.
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