Has there been any inexpensive item that enhanced your system's sound?


For me it was an inexpensive power cord that was laying around for years, a Pangea AC9.  I have it connected to my Yamaha A S2000.  I've tried the stock cord on the Yamaha and then some of my other cords, (Wireworld, VH Flavor 4, Acronlink/Oyaide custom cord and a MAC). I've had lots of amps and integrated amps over the years, and this is the first time the Pangea contributed to making better sound. It surprised me because I had tossed it aside and forgot about it.  Power cord performance is such a crap-shoot and dependent on so many other variables in the audio chain.  Any inexpensive item you've come across that enhanced your system's sound? 
foster_9
Making sure all of one's cables are isolated and not touching walls/floors.
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My last tweak was the Synergistic Black Quantum fuse. It went in my Mystere ca21 pre amp and just made everything better. There is literally more of everything. And it's all the good stuff.
I replaced the Pangea power cord that I praised earlier in this thread connected to my Yamaha integrated and connected another budget cord that I’ve owned for years, the iron lung jellyfish (a hospital grade cord). This cord made a huge difference to the liveliness, bass, prat, and detail of my speakers. Glad I pulled out this forgotten budget power cord.
In a few months, put that Pangea back on the Yamaha, and hey presto! another cheap - actually, free! - tweak.