Optoma NuForce Support Center

How Do I Avoid AC Ground Loops with the Icon DAC?


The Icon DAC employs an innovative floating power supply designed to provide high internal supply voltages and maximum noise rejection from the USB in order to deliver high voltage swings and low noise output in a compact-sized unit. This design feature separates the analog grounds from the USB ground. Therefore, to avoid a ground loop certain precautions apply. Setups to avoid: 1) Using the Icon DAC with a desktop PC USB as source device, with the RCA output connected to an AC-grounded preamp or power amp: In this situation, the Icon DAC is subject to two USB and analog grounds. A ground loop will occur, and the Icon DAC will go into protection mode. Solution: A technique known as "end-of-chain" grounding should be employed. Simply stated, this technique requires that only the audio device at the end of the system chain be earth/safety ground (third pin on AC power cord/AC power outlet). All other devices before the end of the chain should have their earth/safety ground "lifted" (disconnected) by using a common "ground- lift" (G-L) adaptor attached to the end of the AC power cord. Such adaptors have a standard 3-pin female socket on one side and a 2-pin male connection that plugs into the power outlet on the other. These can be purchased at most any hardware store for about $1.00 USD each. Please see the following examples for proper system grounding using G-L adaptors: 1.Analog Source > Icon DAC = No G-L adaptor required 2. PC > Icon DAC = Use G-L adaptor on PC -- NOT on Icon DAC 3. PC or Analog Source > Icon DAC > Preamp/Headphone Amp = Use G-L adaptor on PC/Source & Icon DAC -- NOT on Headphone Amp/Preamp 4.PC or Analog Source > Icon DAC > Preamp > Power Amp = Use G-L adaptor on PC/Source, Icon DAC & Preamp -- NOT on Power Amp You will note that (except for the very first Analog Source case) in each example above, only the device at the very end of the signal chain remains connected to earth/safety ground. Please keep in mind though that in all cases, if a Power Amp of moderate to high power output is used in the system, for safety's sake it must never have its earth/safety ground lifted. Due to high voltages present within, a power amp must always remain connected to earth/safety ground. Also, please remember that whenever a PC/USB to Icon DAC connection is employed, the PC must ALWAYS use a G-L adaptor. 2) Using the Icon DAC with any AC-grounded linear power supply while its RCA output is connected to a preamp or power amp: Solution: This is not recommended as an application for the Icon DAC unless a ground-lift adaptor is used on the Power Supply's power cord as outlined in #1 above. When the Icon DAC goes into protection mode, the LED will blink. As soon as the problem has been remedied, the Icon DAC will resume normal operation. A power on/off reset may be required. Using the Icon DAC as a stand-alone headphone amp with any source device does not create ground-loop concerns.

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