So far I was an enthusiastic Koss Porta Pro - user. However my last two broken me are gone, cable break. In the second it happened after one year. The Pro4AA actually makes a bit antediluvian impression, but in my opinion, better sound than the Porta Pro. All frequencies are reproduced much more evenly and you can also watch many different aspects of music. The closed system is of course much more isolated from the outside world as the Porta Pro. Contrary to some other reviews I find it not too heavy. For the price strong buy recommendation.
