For the last few years, I built the system I wanted as a kid but couldn't afford (Holy moley stuff was spendy in the 70's). Marantz 2270, Advent Bullnose NLA, Dual cs5000. I thought a pair of pro 4aa would complete the system. Off to ebay I went. First pair I bought, on channel was bad. I wrote the guy and offered to send em back. He was cool and said 'just keep em' and he refunded my money. I found another pair from the mid 70's and bought those as well. Though the fit can best be described as 'migraine inducing' the sound was balanced and detailed.
I got curious and decided to take the first pair apart. The wires on the driver had broken and, not being a micro surgeon, gave up. While surfing the web, I found info that said they had a lifetime warranty. I texted Koss and the said to ship them with a check for 9 bucks return postage. Two weeks later, I received a brand new pair of Pro 4aas.
I learned that over the years they used 4 different drivers. While they had retained the medievil torture characteristics of the original 70's pair, the sound was comparatively dead and lifeless. So, what I learned is that Koss support is unreal and, if you can find a good pair, the early ones sound better than the current ones.
I got curious and decided to take the first pair apart. The wires on the driver had broken and, not being a micro surgeon, gave up. While surfing the web, I found info that said they had a lifetime warranty. I texted Koss and the said to ship them with a check for 9 bucks return postage. Two weeks later, I received a brand new pair of Pro 4aas.
I learned that over the years they used 4 different drivers. While they had retained the medievil torture characteristics of the original 70's pair, the sound was comparatively dead and lifeless. So, what I learned is that Koss support is unreal and, if you can find a good pair, the early ones sound better than the current ones.