Channel Imbalance - HELP

It has finally got the better of me.

Ever since my first high-end system bought 15 years ago, I got it home and the left channel was louder than the right. I traced it to the amplifier, took it back to the dealer and funnily enough it was perfect at his place. He was good enough to exchange it for a new one anyway, but when I got it home, exactly the same thing!

I swept it under the carpet and just enjoyed the music. A few years later (with a whole new set of components) it was annoying me again, then I had an issue with one of my speakers and blamed it on that - I got rid of those too.

I was in denial.

Now, 15 years later with not one single component the same as in my system even only five years ago, I did some scientific measurements and sure enough, the right channel is 2dB down on white noise!!!

I did some swapped the L and R channels at the preamp output so the signal was going through DAC and preamp correctly, then swapped for power amp and speakers. You know what this did? - evened out the whole mess! Indicating to me that it is a progressive thing through each component.

What's going on??

Sorry for the long post, but I've had enough!!