What was your first big eye opener with regard to audio?

Back in 1981 heard of a Linn dealer and how good their systems were. I had a kenwood ingratiated amp at the time. Took my amp down and heard a small naim nait ....
The music sounded like real instruments ! 
before then I never though of connecting the two 
thus the rabbit hole appears ........ 

Incrementally adding room treatments and hearing the improvement with each change.

The first jaw-dropping and unforgettable moment -- which launched my 40-plus years of audiophile adventuring -- was hearing the clock bells ringing on then-new Dark Side of the Moon at Tech Hi-Fi in Ann Arbor in 1973. I never dreamed playback of music could sound so real. Probably was on a lowly pair of EPI Model 100s.

Forty years later, the most jaw-dropping single change I ever made in my many systems was installing a direct AC line from our breaker box to new four-plug boxes in my listening room. WAY more difference than any of the many multi-thousand-dollar changes I had ever made in my various systems up until then.

And it cost just $1,200 -- would be even less in most homes.

Steve

Probably my "first" was realizing that the pre amp was the heart of any system. There is no way to tell what is going on in your system until the pre amp is of sufficient quality.But my first "Oh My Gosh" moment, was when I started trying power cords and power outlets. I couldn't believe the difference that they made.

My life changing moments:

1.) Infinity WTLC (after the Servo Static and before the EMITs, used a Walsh tweeter) , Phase linear electronics. The system that started it all, it demonstrated to me that stereos could make a 3D soundstage. Soundstage has been my overriding need ever since.

2.) Audio Research D-79b, SP-6b, Acoustat 2+2 speakers, LINN table. The first system to open my ears to what high end was truly capable of.

3.) Magnapan Tympani I speakers, Mark Levinson ML-2 and ML-1 amp/pre, Goldmund table. Perhaps the single best system I have ever heard, and I have heard the Infinity I.R.S. system at P.S.Audio. It has so weighed on my psyche, I heard it around 1981, that I have since purchased a used pair of ML-2 amplifiers. They are as great as I remember.

4.) My first single ended triode amp. My first build, it uses the 45 triode. It taught me that everything I thought I knew about hi-fi was wrong, or at least over hyped. I now have three in a tri-amped home built Altec horn system. That speaker turned out so well it caused me to buy those Levinson amps for my Sound Lab electrostatics. This system also taught me that equipment doesn’t have to be commercial to be really good.

5.) Lampizator DACs. First a Big 6, followed by a Big 7. Lampizator DACs are indeed different. All of the analog stage is tubed. My Big 7, I loved the Big 6 but I wanted DSD capability, uses an R2R ladder DAC (not a chip) for the PCM decoding, and a separate filter (not a DAC chip) for the DSD decoding. It also uses a tube rectifier and directly heated triode tubes in the output. You can roll the tubes, my preference is for the 300b. There are no chips or op-amps in the signal path. They have turned digital into my preferred source, especially DSD.