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Jon Gerow · 06-26-2006 · Category: Guides

The resistance of modular connectors, adapters and splitters


Years ago, there was this cat named Ohm and he explained to us that resistance sucks.

Ohm’s law, as it pertains to resistance in electrical current, is R (resistance) X A (amperage) = V (voltage.) So you can see, the greater the resistance, caused by either length of wire, gauge of wire or having to go through connectors and/or the greater the current, the less voltage you get.

In simple terms, having a modular power supply may drop your voltage a little because of the resistance between the modular interface and the cable. And using a 20-to-24 pin adapter or any kind of splitter can cause a slight drop in voltage because of the resistance caused by any imperfect contact between the pins of such an adapter or splitter. But on that same note, every single connection you make (PSU to drive, or motherboard, or video card) is another connector that is going to create a little more resistance.

There’s been a lot of scare tactics used to convince people not to go with a modular power supply. And even though there are some valid points made, the reality is that the resistance is quite minimal even at high loads...if the modular power supply is a well thought out design and preventative measures are taken by the user.

For example: A PCI-e cable is going to have less resistance if there’s 3 12V leads on each side of the cable and 3 grounds on each side of the cable. Unfortunately, some modular power supplies may only have one or two wires split into three for each row for a PCI-e connector, so some homework needs to be done on how the cables are constructed when considering a modular power supply.

And when using a modular power supply, adapters or splitter, make very certain that the connection between both interfaces is secure, firm and flush. Make sure all of your connectors are fully seated. This does not only apply to modular power supplies, but also goes for standard power supplies and all of the connections you make to the motherboard, your drives, etc. If you have a connector that is not fully seated, you create resistance. That resistance not only can cause a drop in voltage at the end of that particular wire, but also create heat. Many times I have seen BURNT connectors from cables not being plugged all of the way into their sockets.

On the subject of gold plated contacts: They don't do any good unless they're interfaced with gold plated connectors. In fact, the mating of dissimilar metals is actually more prone to corrosion than if both connectors were tin plated (your typical silver colored connector.)

So if you get a modular power supply that boasts gold plated connectors, keep in mind that it may only be better to have gold on the power supply side of the cable, and only if the modular interfaces on the power supply are also gold plated. Since I personally haven't seen any hard drives or motherboards with gold plated power connectors, I'll pass on gold plated connectors on the peripheral end of the cable.

Contents

  1. Introduction
  2. The PC power supply:
  3. The PC power supply label:
  4. Defining the connectors of an ATX power supply
  5. ATX power supplies DO NOT turn on at the flip of a switch
  6. Testing your power supply's voltage: Software vs. Multimeter
  7. Power Supply Efficiency
  8. The Derating Curve
  9. Power Factor Correction
  10. The resistance of modular connectors, adapters and splitters
  11. Conclusion

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