![]() The bottom line is that unbalanced keyboards can often be connected to an interface or console directly without problems, but if there are signal or hum problems you'll have to go the DI or line-isolating transformer route anyway. well over 100k?) that a DI box provides, rather than the 10k? or so impedance of a standard line-level input.Īnother consideration is that most studios are well-equipped with mic tie-lines and mic preamps, but less well with line-level tie-lines and line inputs - and unbalanced runs are more prone to interference and ground-loop problems than balanced runs.įinally, mic preamps are capable of adding 'sonic character' to a sound through transformer, valve or solid-state distortion artifacts, which may well be deemed beneficial and appropriate. For example, some very early electronic and electric keyboards do work better into the very high input impedances (ie. Running a keyboard via a DI box has a number of other useful benefits. (There are some preamps and interfaces that allow phantom power to appear on supposedly line-level and DI connectors! I came across a brand-new one only a couple of weeks ago.) Phantom power can, and occasionally does, destroy the output stages of keyboards and other equipment, so taking simple steps to protect against an inadvertent accident might be deemed sensible. It also gives complete protection from phantom power. Line-level transformer isolators are available, but are far less common than DI boxes, and the good ones are generally very expensive.Ī DI box inherently contains a transformer and can be used to provide galvanic isolation, preventing ground-loop issues. The only safe and practical way to cure this problem is with a coupling transformer of some kind. However, given that many keyboards are not double-insulated and therefore require a chassis safety earth via the mains power supply, in some cases there may also be ground-loop problems. Not all line inputs are sufficiently sensitive to handle the output from keyboards effectively, but if your desk, recorder or interface has line-level inputs with sufficient gain available, you can indeed connect your keyboard directly and get an acceptable signal. SOS Technical Editor Hugh Robjohns replies: In the majority of cases, electric and electronic keyboards provide an unbalanced output at a level typically 10-20 dB below standard line level. If you go through the DI box to a suitable mic preamp, you can also benefit from the tonal colour the preamp offers. However, the best way to protect against ground loop, phantom power and faulty wiring problems that could arise, and even damage your equipment, is to connect the keyboard to a mic input, via a DI box, instead. It's possible to connect the line outs of keyboards directly to the line inputs of your interface, mixer or recorder, and some musicians do. I've always stuck keyboards straight into my interface, desk or whatever: plenty of level, minimal noise (if any), and no hassle. boxes with Keyboards - but it still applies to the GR-55 and its unbalanced Line Outputs This article was written about using D.I. There are many choices of Passive DI Boxes (Just Google) Box ) with an isolated Ground Lift - to solve Ground Loop Noise and Hum. Sometimes the GR-55 > PA connection may benefit by using a stereo Passive Di Box (as opposed to an Active D.I. ![]() Stereo Audio/Video interface to low level inputs ![]() Variable Input pad for mic or instrument inputs A 20Hz to 20kHz frequency response ensures the Dual RDB will function transparently with any high quality audio source. The Dual RDB's variable level controls allow volume control to be set at the source rather than in the studio, AV room, audio closet or installation rack. The Dual RDB accepts 1/4" TRS and XLR line level inputs and outputs mic or instrument levels. The unit has two high quality isolation transformers that prevent ground loops when connecting various systems together. The Dual RDB is the ideal interface solution for any application where stereo or dual line level signals from recording interfaces, computers, mixers, iPods, consumer audio or video machines need to be connected to XLR microphone or ¼-inch instrument level inputs.
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