I was curious about the specs on that fan. According to info provided on the Mouser Canada website, that fan works with a fixed DC voltage of 24 volts. But the RMX fan circuit supplies a varied voltage to the cooling fan depending on the heat generated within the chassis. With the published fan specs, I suspect that the fan which you installed may not be appropriate for the RMX850. If the voltage provided by the amp's circuit is far lower than the required 24 volts, that could damage or even burn the fan motor. I would suggest that you verify the situation to avoid problems.
There were a couple of forums where people substituted this specific fan for the stock one as a means to quiet things to a lower level (you can still hear the fan, but it is not as "in your face"). This fan does not afford the air flow of the stock fan, but I will always use it in an air-conditioned room.
This is the same fan PENG chose so I feel pretty good about the electrical end of things.
To that end, the spec sheet indicates an operating range of 12 to 27.6 Volts, so this fan can be operated as variable speed.
My understanding is if it were powered under 12 Volts, the fan may not spin; however, the fan starts whenever I turn on the amp (which would generally be the lowest temperature situation resulting in the lowest voltage).
Also, there were reports on a couple of forums where this fan was used with good result.
Interestingly, I have never noticed the original or replacement fan speed changing!
