Thanks for the feedback. We are aware that some users consider the transformer and fans loud. BUT If you have big vibrations, you should consider that you have a faulty unit and send it in for service. I am fairly certain no units ship with big vibrations or excessive audible noise (it is checked). Some people are more sensitive to it than others.
The DC power input at the back (mechanical switch) was investigated and was not lower cost than the soft power. That being said, if there is another generation meter -- it likely won't be at this price point and thus it will probably have the power input filter with switch like most other products. Those are much nicer indeed.
Keithley 2000 and 34401A transformers are near perfectly silent. The DMM6500 can be heard from across the room. At what point noise becomes an issue can be personal but a large difference can objectively be established.
Of course, no disagreement here. The 65xx transformer was designed from scratch as the KI2000 model was too expensive and not suitable for 65xx (due to the DAQ model) As such, we did take steps to reduce the transformer hum and even quantify it to a level that
most people found acceptable. However, since it is not silent, there will be those who are bothered by it. A new design to make it quieter without costing more, might be feasible in the future.. only time will tell. I dont think enough formal complaints have been made to drive change though - and there are a lot of these units in the field.
I am always looking to improve the design and can better do so with formal reports filed by customers (not me representing web forums.. haha)
ahem, management likes reports, statistics and data, not complaining design engineers..