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
Like Elizabeth: Retired

My Reed Sound Level/Pressure Meter. Really helped set up my speakers to best possible position and rearrange furniture to reduce standing wave reflections.

For goeff: Quit flying Immelmans as it disturbs vestibular perception.
Freezing things in the home freezer. CDs, LPs, Blu Ray, CD players, headphones, cables, power cords, what have you.
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Hockey pucks.  OK, I don't know that they actually have any impact on sound quality, but due to space limitations, I have to stack some components in my bedroom and it helps give some breathing room between them, hopefully it will help prevent an early death from heat.