Hello internet folks!

So I bought a distortion pedal, bout a month back, and now I'm having problems with it. I thought the volume was a bit unstable recently, but now I'm absolutely sure. I had it turned up pretty big, two thirds of the way or so, and in between, it just went down to like a quarter or less of the volume. Turned it up to compensate, a minute later, the volume is back to full - which means, as I increased the volume in the meantime, that I nearly blew out both the amp speaker and my eardrums.

I'm running the pedal with a rechargeable 9V battery, as I don't have a power adaptor that's buzz-free (note to self: tell the guitar store guy it's likely faulty). I'm not sure whether it's the pedal or the batteries. I also made the strange observation that the volume decrease when I palm-mute. Perhaps I'm going nuts, but it certainly seemed that way, every time it got less loud, it was when I palm-muted. No idea what to make of that, honestly.

So, can anybody tell whose door I'll have to knock down in order to get this fixed? I'd rather not go through the hassle of getting a replacement (though the customer support are always super nice and have it replaced within a week or so without any problems), so I'd be grateful if anybody's got an idea what's wrong with it.


HashtagMC  ok it may be the bypass switch is not properly engaging. if you can check out with a battery adapter then i would to rule that out. 
Some pedals don't work well with rechargeable batteries so it might be worth trying a regular 9v battery.  It's probably not the issue but it's worth a shot if you have a 9v battery laying around.  If it's not the bypass switch not engaging, or the battery then it could also be one of the wires on one of the jacks is starting to break off or come loose.  The jacks can sometimes twist around when you plug in and unplug your guitar causing the wires to touch stuff they shouldn't or to break.  The same can be true of the switch.  Just have a look and be sure nothing is coming loose or looking like it might break.
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It might be the nature of the pedal. Some distortion pedals are so compressed that chugs sound the same volume as single notes, and they are perceived as "quieter" because you expect chugs to be louder. I would always recommend a wall plug of some sort to power your pedals (I have a t-rex for all my 9 volts) since you start saving money fast, 9 volts don't last long in pedals.
VanhalenVai no, volume changes even if I play the same part, in the middle of, say, strumming an open A major for example. And a power adaptor introduces huge amounts of buzzing (either faulty or, more likely, fucked up wiring in the house (no sane person wires the ground floor bathroom to the same breaker box as the 2nd floor bedroom)), and I can't afford one that has fancy noise-protection-cancelling-whatever.