Cheapest was removing the cover from my phono preamp. Opened up the sound almost metaphorically. Refitting the lid closed in the sound. And never play records with a lid on your turntable especially closed.
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?