Note that I’ve seen much cheaper on Amazon, but not from a known vendor, so I can’t vouch for them. It’s about $500, but you can easily get away with a lower wattage (500 or 250) model for less than $250. Tripplite sent me one of these as well: the excellent 1000-watt IS1000HG (Hospital Grade) with four outlets. ![]() Slightly cheaper than an online UPS, but absolutely effective against all kinds of line noise is an isolation transformer. ![]() If you’re not worried about defeating ground-loop noise, you can get away for not much more than $100 with a UPS that advertises pure sine wave output. It’s also much less-expensive than one of those high-end power conditioners you see marketed to gullible audiophiles. It costs several hundred dollars less, but doesn’t provide battery backup power.Ĭondition your power with the Tripp Lite IS1000HG isolation transformer The Tripp Lite IS1000HG isolation transformer I mentioned earlier will also clean up AC line noise. But darn if it isn’t 100 percent effective at providing protection against power surges and outages. It’s also heavy, about the size of a small dehumidifier, and it has some features (such as USB monitoring, so that it can gracefully shut down an attached computer in the event of a power failure) that have nothing to do with noise elimination. That device was selling for nearly $900 when I updated this article. Tripp Lite sent me its model SU1000XLCD UPS to clean up the super-dirty AC in my apartment. Line interactive UPSes are more expensive than the standby alternative, which keep switch to battery power on demand. If you connect the output with DC offset directly to the coils of the transformer a DC current will flow in the coil that may or may not affect the way the source behaves.īelow is a picture of what is under the hood:Įveryone with a notebook should have one of these in their bag (along with an EDID emulator), so the next time you do a presentation, you will have the purest sound along with sharp and trouble free video image.This type of ground loop isolator, for coaxial cables used with over-the-air antennas and cable- and satellite-TV equipment, can eliminate both visual and audible noise. Most audio sources should have these AC coupling caps on their outputs anyway (so their average output voltage is not biased at some DC voltage), but once in a while you have a source that has a DC output offset. The input side (the female 3.5mm at end of cable) has DC blocking capacitors, so it is a good idea to make sure to not reverse the input and output. So if your load is 5K Ohm, adding the isolator in front of it, the source still sees a 5K Ohm load impedance. It uses 1:1 audio transformers therefore it does not change the impedance. In order to isolate this Bias level from the transformer coils, DC blocking capacitors are employed in the GLI-35mm. Some audio source equipment may have a DC bias voltage on their audio signal. The input side incorporates DC blocking capacitors. In most cases the unit can be used in either direction, however it is designed so that the Female 3.5mm mini-stereo connector is to be used as input and the male connector is the output. The GLI-3.5mm is simply inserted in series with the audio and it literally eliminates the ground connection between the two sides, passes all the audio while filtering out any noise using high performance audio transformers. Line-level audio is a very tiny low-level signal, so any noise in AC ground, even as little as 0.004v, will be quite audible – yuck! This is because, by doing so you inadvertently eliminated the ground loop. In fact you may have noticed that if you disconnect your notebook power supply and ran on batteries the noise has gone away. On the other hand unbalanced signals, such as the one coming out of your notebook, have no reference other than building/AC ground. Any noise in the ground between the source of the Audio signal and the amplifier is automatically ignored. Professional equipment have balanced audio which uses a + and a – signal for each L/R side and therefore does not rely on ground. Have you ever connected a PC or notebook to an audio amp or a TV and gotten all kinds of ugly noise? Most people would answer yes, and that’s because the audio output from these devices are not balanced. Uses proprietary audio transformers and filters for total elimination of any spurious buzz and hum in the audio. Perfect frequency response of +.03 db from 20 to 20,000Hz. Eliminates ground loop noise between any audio source such as a notebook PC and audio equipment. GLI-3.5mm Stereo Audio Ground-Loop Isolator & Filter with 3.5mm connectors.
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