Best bang for the buck


What’s been the most cost effective item you purchased for your system? 
I will go first- a Zerostat I bought 40 years ago. Next most cost effective purchase has to be a Denon DL103R cartridge which I bought new for $300. 

zavato

About 10 years ago, I bought a McIntosh MC 240 for $50.  Pretty sure the tubes were original and the unit was in good working order. Of course I brought it to Audio Classics for an overhaul, but well worth it.