This is disturbing and confusing.
I have thoroughly tested the MA-505 and the DD-40. Both are functioning very well. I have an MS in Physics and have spent my entire career developing very high end medical and communications equipment. I thoroughly understand the mechanics and electronics of TT and cartridge behavior.
I have tested the bearings on the MA-505 arms using my own techniques and using the WallySkater. Very fluid, no rough spots both vertically and horizontally.
I've recapped the TT. The rotation speed is rock solid. Test records indicates a very stable speed.
I have listened to the Koetsu on my WOW XXL table using a brand new Audiomods 6 arm. Both are very modern products. I very much prefer the sound from the DD-40 and MA-505. The arm that came with the table (Acoustic Signature TA-2000) has been removed because it is so difficult to use.
What arm and table did the people who purchased a Koetsu in the 80s use? Were all arms and tables insufficient then?
What else should I look for in the DD-40 and MA-505 that will tell me that they're not good enough for the higher end cartridges? I test every piece of equipment that I put in my system with a spectrum analyzer and an oscilloscope. I can measure and optimize distortion, anti-skate, tracking force, speed stability, and frequency and time domain response. Performance is very important to me.
In summary, what tests can I perform that will show me that the DD-40 and MA-505 are inadequate for higher end cartridges? I need to see some data before I am convinced that my older tables are insufficient.