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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 the product:

• Allows you to control the speed of the fans inside your case with ease
• Adjustable output voltages from 7V ~ 12V DC each channel
• 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 was.

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 into place.

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.

In Use

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 little feature.

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.

Multimeter Voltage Reading (V)
12V Rail

This 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.

Rheobus highest setting without fan

This reading was taken to compare with the 12V rail to see how much voltage the rheobus used itself.

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 welcome.

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
No instructions.

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