I have to say that I have a system from here
http://www.lowcostcncretrofits.com/ and there are geckos inside, I am not sure what the numbers are 320 340 but I have 2-600oz servos, and 1-1200 and NONE of the HUM.. It is true that you will not hear them while running but I feel like this will result in a fault at some point in time. I have the geckos and a galil 18x2 all withservos and my servos do not HUM. It took a little while to tune the Galil but while tuneing them I found that the slightest HUM would soon result in a fault. There may be a little hum allowed with geckos but it realy shound not be very loud, or there is a problem...
A servo with a bad hum is poor tuneing, or loose motion, or poor amp tuneing, or an encoder problem.
At this time we have only tried motor tuneing and checked for mechanical slack, and both are ok.
We have not tried amp tuneing at this time, but will I am sure.
I am pretty sure that the encoder is ok, as it would have faulted out the drives during his testing.
Ok, for a minute I will go along with the crowd and say humming is ok. BUT I just can't.
Does everybodies HUM? dgoddard's is 3 axis and two different hums(z,y same and x is a bouncing hum), so if there going to hum I am sure that they would do it consistantly?