Your most disappointing purchase or audition?

During my sophomore year in HS, I purchased a 40wpc integrated amp, the Kenwood KA-305 for full list price,$200. That was a lot of paper route money in 1979!

http://vintageaudio78.blogspot.com/2010/11/kenwood-ka-305-photos.html

It sounded quite good with my dual tt and polk 5 speakers. I had it all through high school and at the end of my sophomore year at college, I sold it for $100 and bought the latest 100wpc Kenwood KA-7x (list price $400).

http://www.turbosquid.com/3d-models/maya-kenwood-ka-7x/693920

With tremendous anticipation, I hooked up the new model and it absolutely sucked. It had way more features and likely used op amps vs the old discreet model. It was lifeless, had no dynamics, and didn't drive the 4 Ohm Polks worth a crap. I learned the hard way that specs were meaningless and you had to listen to determine if a component sounded better or worse. Two years later, I got a closeout deal on a Denon PMA-737 60wpc integrated (paid $200 for a $300 unit) and it just mopped the floor with the 100wpc $300 Kenwood.

I have said it before in other threads, but since this thread asks the question, I would have to say the Pass Labs X 250.5. I used it in single ended mode, which I was told later was not optimum, although I never read that in all of my pre-purchase research. I bought it and auditioned it with 5 different speakers in my system, and in each case, the sound was thin and electronic. It was a really shocking disappointment.

Other than reliability/service issues (decomposing surrounds on Zingali speakers and horrible Audible Illusions repair service come to mind) I don't hink that I've ever bought anything that I later really regretted (and I have bought a lot over the years). However, I've definitely heard some clunkers on demo:

I remember hearing the original Martin-Logan Sequel at IIRC Innovative Audio in Brooklyn Heights about a million years ago. That was some really bad integration of a dynamic woofer and a panel. It might have been one of the first pairs manufactured and the underdamped woofers were just a mess. I believe that later examples of that model were much better sounding (there was also a Sequel II at some point that addressed the issue). I also heard a demo of the big B&O room corrected speakers in their Beverly Hills showroom +/- ten years ago that was so bad that I'm still left wondering if one or both of the speakers was defective.

Cary SLP05. Spent big dollars (for me) to purchase it used ($4k) and I never could get it to sound up to its reputation even after rolling tubes. In fairness, the unit's performance may have been a simple case of poor system synergy in my setup.

Also, Cary 303/300, no better than a boat anchor imo. No benefit of the doubt here though.

One man's meat is another man's poison.