User manual RANE MH 4

[. . . ] This unit comes with an outboard power supply which does not ground the chassis through the line cord. The MH 4 can be grounded either to another chassis which is earth grounded, or directly to the grounding screw on an AC outlet cover by means of a wire connected to this chassis grounding screw. Manual-2 PHONE Output jacks These stereo ¼" TRS jacks accept standard ¼" TRS stereo headphone plugs. Individual LEVEL controls These control the volume for each set of headphones as they are driven from the INPUTS. It's always a good idea to keep this control turned down before plugging in a pair of phones, then turn it up slowly. POWER switch and LED Your basic, straightforward power switch. When the yellow LED is lit, the MH 4 is ready to go. INPUT jacks These are automatic balanced/unbalanced Inputs, which accept either a ¼" TRS (TipRing-Sleeve) plug for balanced operation, or a ¼" TS (Tip-Sleeve) plug for unbalanced operation. [. . . ] Chassis tying the shield at each end also guarantees the best possible protection from RFI [radio frequency interference] and other noises [neon signs, lighting dimmers]. THE NEXT BEST RIGHT WAY TO DO IT The quickest, quietest and most foolproof method to connect balanced and unbalanced is to transformer isolate all unbalanced connections. The goal of transformer adaptors is to allow the use of standard cables. With these transformer isolation boxes, modification of cable assemblies is unnecessary. Virtually any two pieces of audio equipment can be successfully interfaced without risk of unwanted hum and noise. Originally named for its use to convert the high impedance, high level output of an electric guitar to the low impedance, low level input of a recording console, it allowed the player to plug "directly" into the console. Now this term is commonly used to describe any box used to convert unbalanced lines to balanced lines. THE LAST BEST RIGHT WAY TO DO IT If transformer isolation is not an option, special cable assemblies are a last resort. The key here is to prevent the shield currents from flowing into a unit whose grounding scheme creates ground loops (hum) in the audio path (i. e. , most audio equipment). Do not be tempted to use 3-prong to 2-prong "cheater" adapters to lift grounds. It is true that connecting both ends of the shield is theoretically the best way to interconnect equipment ­ though this assumes the interconnected equipment is internally grounded properly. Since most equipment is not internally grounded properly, connecting both ends of the shield is not often practiced, since doing so can create noisy interconnections. A common solution to these noisy hum and buzz problems involves disconnecting one end of the shield, even though one can not buy off-the-shelf cables with the shield disconnected at one end. The best end to disconnect is a matter of personal preference and should be religiously obeyed; choose inputs or outputs and always lift the side you choose (our drawings happen to disconnect the outputs). If one end of the shield is disconnected, the noisy hum current stops flowing and away goes the hum -- but only at low frequencies. A one-end-only shield connection increases the possibility of high frequency (radio) interference since the shield may act as an antenna. Many reduce this potential RF interference by providing an RF path through a small capacitor (0. 1 or 0. 01 microfarad ceramic disc) connected from the lifted end of the shield to the chassis. compressor A signal processing device used to reduce the dynamic range of the signal passing through it. For instance, an input dynamic range of 110 dB might pass through a compressor and exit with a new dynamic range of 70 dB. The modern usage for compressors is to turn down (or reduce the dynamic range of) just the loudest signals. When used in conjunction with microphones and musical instrument pick-ups, compressors help determine the final timbre by selectively compressing specific frequencies and waveforms. connectors Audio equipment uses different styles: RCA An unbalanced pin connector commonly used on consumer and some pro equipment; aka phono plug XLR A 3-pin connector common on pro audio equipment. [. . . ] phase shift: polarity refers to a signals reference NOT to its phase shift. Being 180 degrees out-of-phase and having inverse polarity are DIFFERENT things. Defined to be the ratio of the center frequency f divided by the bandwidth BW for a bandpass filter. signal-to-noise ratio The ratio in dB between a reference level and the noise floor. [. . . ]