Your most disappointing purchase or audition?

Parasound CD1. I had high expectation for the Parasound, but my cheaper Emotiva ERC-3 sounded better!

In the late 80's I was returning from a long overseas assignment and looking to re-enter the audio hobby. I visited a local dealer and heard a Krell 300 integrated with a Meridian CDP and Thiel CS1.5 (could have been 1.2's) speakers. I thought my ears would start to bleed. Just horrible

So far it appears that the Krell integrated may be winning on votes as the most hated audio purchase.

Regarding Krell KAV 300i: I had it for some years, and though I would not call it my worst buy, we never became friends. I changed to Krell KAV 250a + 250p (two boxes). In terms of price/quality, the 250p was perhaps my worst disappointment. I still remember the big smile when I changed to the Aesthetix Io. Hello, music! That was with Krell FPB600, the first Krell I liked. In fairness, it should be said that I sold the ones I did not like (and eventually also the 600) for OK prices, I lost money, but it could have been worse.
Regarding Atma-sphere amps, I can only report my own satisfaction over the last couple of years with MA-1s. Sometimes, a tube can blow or arc, yes, it happens in all tube gear, but the amps have functioned with zero problems otherwise. The upgrades have been fairly priced and worth the money. Also, customer help and just general communication with Ralph is a big plus. To me, in my system, this is music in a way I never got it, with the Krell (and Dynaudio Consequence speakers). So I would encourage other A-goners to explore OTL sound (I have no commercial interest whatever). And as you will understand, with experience from three steps of the Krell ladder before I moved up (yes, up) to the MA-1s, I read Stereophile with great caution. "Almost tubelike"!! They said that about the FPB600, back in 97, and recently about a new big s-state amp. I have heard it before. "Almost"? Not to my ears.

Yes Roxy, I too remember hearing the Kav Krell 300i integrated a few times at a dealer many years back. If I recall it wasn't too expensive, at least not for a Krell but it wasn't at all impressive, actually much worse than that but it did have a nice case and low profile, if looks are important. I'm sure a few unsuspecting purchasers got hoodwinked on that one.