User manual ALLEN & HEATH PA28

[. . . ] PA Series Unpowered Version USER GUIDE Publication AP5195 Limited One Year Warranty This product is warranted to be free from defects in materials or workmanship for period of one year from the date of purchase by the original owner. To ensure a high level of performance and reliability for which this equipment has been designed and manufactured, read this User Guide before operating. In the event of a failure, notify and return the defective unit to ALLEN & HEATH Limited or its authorised agent as soon as possible for repair under warranty subject to the following conditions Conditions Of Warranty 1. The equipment has been installed and operated in accordance with the instructions in this User Guide. [. . . ] That is why the fader is marked `0' at its normal operating position, the point at which all the channel signal is fed to the mix. If the fader is moved above `0' it produces more output and therefore has gain boosting the signal level up to a maximum of +10dB. As the fader moves below `0' it produces less output than its input and therefore has attenuation. The infinity mark at the bottom position represents maximum attenuation, in other words the signal is turned off. The dB explained Because of the way the human ear responds to sound, the decibel uses a logarithmic rather than linear scale. Regarding audio voltages, dB = 20log(Vout/Vin) where Vout is the output level expressed as a voltage, Vin the input level. For rule of thumb, gain is: +10dB = +6dB 0dB -6dB -10dB -20dB -30dB -90dB = = = = = = = 3x at fader top 2x 1x (unity) 0. 5x 0. 3x 0. 1x 0. 03x 0. 00003x at fader bottom PFL Press this switch to listen to the channel signal in the headphones and display its level on the main meters. This lets you check each channel signal independently without affecting the outputs. The channel PFL switch LED and the big PFL/AFL indicator below the main meters light to warn that PFL has been selected. PFL stands for Pre-Fade Listen. It sends the signal taken just before the channel mute switch and fader to the engineers personal headphones monitor and console meters. This means that you can check the signal while the channel is muted or its fader down. Note that AFL, as found on the FB1 and FB2 masters stands for after-fade listen. Using PFL Use PFL to check sound quality and the channel gain setting when plugging in different sources or when you suspect a change or problem with a particular signal. This lets you set up the signal before you introduce it into the monitors and house mix. You should hear the signal in your headphones and see its level displayed on the console meters. Adjust the gain control so that the meters read an average `0' with loudest peaks no more than `+6'. The above shows how wide the fader control range is. At minimum position it is just 1/30000 of the original, effectively off. Write-on Block Use the white block for labelling the channel using chinagraph marker, felt pen, adhesive label or tape, or magnetic label strips. Do not use chemicals or solvents to clean the blocks. PA User Guide 17 The STEREO Channel Dual Stereo Inputs Each stereo channel has two independent stereo inputs, ST1(3) and ST2(4). For convenience, one uses RCA phono connectors, the other uses TRS jacks. The two inputs mix together to feed the channel strip, or ST1(3) can be routed direct to the LR mix instead, leaving ST2(4) to feed the channel. This provides a very flexible arrangement for mixing up to four stereo sources. ST1(3) INPUT RCA phono inputs for connecting line level stereo signals. These connectors are popular with consumer and semi-professional equipment such as tape deck, video camera, computer, CD and MiniDisc players. ST2(4) INPUT TRS jack inputs for connecting line level stereo signals. [. . . ] They are impedance balanced and can work with balanced or unbalanced inputs. It does not break the signal path to the AB XLR outputs. MAIN OUTPUT BALANCED PIN2 = + AB MAIN OUT Rear panel XLR line outputs for connecting to external line level equipment such as speaker processors and amplifiers. Electronically balanced outputs use a 3 wire connection to provide improved signal drive and interference rejection when plugged into balanced equipment inputs. Signal hot (+) = pin 2, signal cold (-) = pin 3, ground (cable shield) = pin 1. [. . . ]