The DA-401 is a very light tonearm which cannot bear Denon's venerable DL-103 MC cartridge heavyweight oldie : tracking force goes to 2g tops and the equivalent mass for the wand amounts to only... 6g.
The recommended cartridges were Denon's newer DL-303 at first or, later, the DL-305 which both had much better compliance than the 1963 heavyweight.
The 401 did keep the Dynamic Damping system inaugurated much earlier in the 70s - some people like it, some people don't.
What is funny is that Denon's earlier, heavier, tonearms did sell much better : the DL-103 did survive the Ultra-Low-Mass fad of the early 1980s, the DA-401 did not.
More right here.