I am a noob to high-end audio, so don't judge.
I use a Pioneer SX-277 connected to my Sony MDR CD550 headphones, because i needed an amp to drive them.
I know, getting a dedicated headphone amp is better, but this one was just lying around and i don't have money atm.
My amplifier is kinda oldschool, and with age comes problems. The balance isn't working properly anymore. Sometimes it completely
cancels out left or right, at random, and when i turn the knob around a couple times it works again.