alright .. assuming that the battery is new here's a list of things that might be wrong, in no specific order:
bad electrical connection somewhere (bad wiring/pots/input jack) due to whatever reason (cold solder joints/broken wires/loose fits with mechanical connections such as a loose iput jack with a patch cord)
a guitar that isn't set up properly, I went through two full setups with my six string with emg's to get them to sound "proper" (clear notes, no buzzing .. etc) as emg's are a lot more sensitive to setup details than passive pickups are in this regard
last thing that I can think of that's "wrong" with things: your emg's have an actual problem with them and are defective. in this case the only thing to do is replace them but seeing as emg has a handle on how to make their pickups bulletproof this is the least likely thing IMO
some questions: how does the output differ from your strat? is it higher or lower? also, what is it that you don't like about the 707's? saying they sound horrid is a start, but being more descriptive would be helpful. what are the things you don't like about it (too much bass/mid/treble in the voice? doesn't do something you need it to like push the amp or clean up well?) in comparison to your emg equipped strat?
the 707's in the schecter will sound different than the 85's in the strat because the schecter and strat are made with different body woods, and because those two are very similar in voice (707 being the seven string equivalent of the six string 85) you're also going to be quicker to notice the differences. last thing I can think of is that you might not like emg's in the schecter (or at least the 707's. you might like the 81-7 or 60-7)
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