I asked the same question directly to David Zhezhe.   He answered: "The MK III and MK IV are both based on the same SEPP OTL in Class A design, however the MK IV has a slightly different circuit implementation as well as tubes for better overall performance. The SE version of the MK IV...

Just one help. I bought one Fostex modded on ebay from mayflowerelectronics. The sound is good, the hardware (headphone) is broken. I have received two weeks ago. Below the Photos. I noticed some strange marks on the cups, they looked cracked and glued. This morning I found them open and...

Quote: Wich one do you prefer (between HD650 and DT990) ??? I' have HD650 and I'm thinking to buy a DT990.

One question. I have Burson HA160 hedaphone amplifier and Sennheiser HD650 that works very fine with my amp. I'd like to buy one Beyerdynamic DT990 600ohms. Somebody hear has yet tested DT990 600 with Burson solid state ampli HA160? I'd like to know how it works and if works fine or if is better...