I’m sure every computer user knows how loud CPU, case
and PSU fans can be. It can be distracting and downright
irritating at times, especially if you are like me and sleep
in the same room as your computer. This is where fan controllers,
or rheobusses come in.
The fan controller I’m reviewing today the Noise
Isolator RH-35SE Rheobus. I picked it up
for AUD $25, not expecting too much for a cheaper rheobus.
Here are the specifications from the website I ordered
it from, as well as the manufacturer’s image of
• Allows you to control the speed
of the fans inside your case with ease
• Adjustable output voltages from 7V ~ 12V DC each
• Each channel is rated for up to 20W, providing
enough power for 4-16 fans
• Multiple fans can be connected to each channel
• LED backlight around the knobs
• Printed circuit board eliminates wiring mess
• 3-pin fan headers for easy fan connection
• 3-pin extension wires included (2)
• Looks fantastic in the case
• Connects to the power supply via Molex connector
• Mounted on a stylish stainless steel face plate
• Comes with two interchangeable front face panels
(1 x silver, 1 x black)
What’s in the box?
When I picked up the purchase, it came in a non-descript
cardboard box that was bent and slightly squashed. It
must have been in the warehouse for a fair amount of time.
A quick search on Google helped me find out who the manufacturer
Luckily the contents of the box were
protected in a bag of bubble wrap, which once empty revealed
the rheobus, 2 plastic bags with two 3-pin fan extension
leads each, a green Molex “y-cable,” mounting
screws and a plastic bag wrapped around the rheobus with
the two face plates (black & silver). There was no
hint of a manual or installation guide anywhere.
Two things I would like to mention
at this point are:
a) the Molex “y-cable” appears
to be UV-reactive, but I can’t test it at this point
in time as I don’t have any UV lights at hand (I
will report on this in the forums once I get the chance
to test it),
b) I received twice the advertised amount
of fan extension leads. Having two separate bags makes
me think of two things, either the manufacturer or the
re-seller packed the extra bag by mistake, or the re-seller
thought it made more sense to pack enough leads to use
with each channel of the fan controller. In any case I’m
not complaining, as I needed all four (more on this later).
I realised I had a small problem when I saw that my
case fans were using 4 pin Molex passthrough connectors,
and I only had 3 pin fan cables at hand. Scissors, a soldering
station, and an old Molex “y-cable” (not the
new green one ?), sticky tape and 10 minutes work fixed
that. That was 2 channels on the fan control down. Now
for the other two.
My CPU fan is the Coolermaster Aero
7+, which those who own one would know, uses its own variable
resistor to control its speed. That paid a visit to the
corner of my desk with the soldering station too. I also
did the same with my chipset fan, which had overdrawn
the power output from the motherboard, and had been using
an extension cable with bare ends jammed into a Molex
plug. I figured it would be a little safer this way.
Installation of the rheobus itself is pretty easy, if
you have a case with a removable cage its easier still.
The mounting holes are a fair way back along the mounting
frame so if you plan on installing a floppy drive, install
that first below, and then the rheobus above it, as it
will make things easier when trying to screw the rheobus
Installing the fan cables, however, was
a different matter. Due to the small size of the device,
and how far back from reach it is from inside the case,
connecting the fans when it’s installed would be
almost impossible. I think the idea it to connect the
extenders first, and then install the drive, but if that's
not possible, like with my CPU fan cable, try to hang
the cable out of the bay and connect as you are installing
the rheobus. This can get a little tight, especially with
case fans at the rear of the case, but that’s what
the extenders are for.
Using the device is simple, turn the knob left and the
fan speed decreases, turn the knob right and the fan speed
increases. My only real issue is that the knobs are completely
smooth, no easy-to-grip grooves that I can turn with a
single finger, I need to use my forefinger and my thumb
to turn it.
When the computer is powered up, bright blue LEDs light
up from around the controller’s knobs, the light
of which is accentuated by the acrylic cover. Also, when
reducing the speed of a fan, the brightness of the LED
of that knob is also reduced. It’s not too noticeable,
and only the middle work the best, but it’s a nice
Fan Speed and Voltage Differences
I used a digital multimeter to test
the output voltages of the rheobus, and compare to the
12V rail directly from the PSU.
To get these readings I am connecting
the probes of the multimeter directly to the Molex plug
of the passthrough connector for a 12V 120mm fan.
The law of parallel circuits states that
voltage stays the same across all branches, and as the
multimeter is being connected in parallel to the fan when
attached to the rheobus, the voltage read by the multimeter
will match the voltage that the fan receives.
Voltage Reading (V)
reading was taken directly from one of the Molex
plugs coming from the power supply, to provide a
reference voltage to compare the outputs of the
|Rheobus highest setting without fan
This reading was taken to compare
with the 12V rail to see how much voltage the rheobus
|Rheobus lowest setting without fan.
This reading was taken to compare
with the lowest setting result when a fan is attached.
|Rheobus highest setting with fan
This reading was taken to see how
much voltage is available to an attached fan when
the rheobus is at its highest setting.
|Rheobus lowest power with fan
This reading was taken to see how much voltage
is available to an attached fan when the rheobus
is at its lowest setting
The difference in voltages between the 12V rail and
the output from the rheobus is to be expected, as it needs
to power its own circuits, but the differences between
the output with and without the load of the fan are concerning.
The output voltage should stay constant whether or not
there is a load on it, but the extreme difference between
lowest setting with and without load, 6.34V and 9.54V
respectively, gives me reason to believe that the controller
can only just handle a single fan per channel. If a second
fan were added, I doubt the rheobus would be able to supply
enough power to run the fan.
This aside, just over 6V is an ideal level to set as
the lowest point, as some fans, especially LED fans, will
not run with less than 5V, so this margin of safety is
The 11.37V available to the fan is almost 800mV below
the 12V rail, and therefore the fan will not spin as fast
as it could when connected directly to the PSU, but the
difference is small and the difference in airflow should
be negligible, especially with a larger fan, like the
120mm in use.
I didn’t expect too much when I purchased this
rheobus, with AUD $25 being at the lower end of the spectrum
for fan controllers, but I am pleased with its performance.
If you are looking for a simple device to do the job,
without all the flashy extras of the high end devices,
this rheobus probably suits your needs, provided you only
use one fan per channel.
However, I would have liked to have seen 3-pin to 4-pin
Molex adaptors for use with case fans and CPU fans that
require the Molex connector.
Fits in the 3.5” bay
4 fan channels
LED brightness change according to fan speed
Matches silver and black cases
Provides almost all the necessary accessories to install
Hard to connect fans once installed
LED brightness range is to low
No 4 pin Molex adaptors
Voltages vary depending on load