<!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">





 <meta name="generator" content="Adobe RoboHelp 9">
<title>Automixer</title>
<link rel="StyleSheet" href="HtmlHelp.css" type="text/css">

<style title="hcp" type="text/css">
<!--
span.hcp1 { font-weight:bold; }
p.hcp2 { font-weight:bold; }
span.hcp3 { font-weight:normal; }
p.hcp4 { margin-bottom:0; }
-->
</style>
</head>

<body class="ns-0 ltr">
<div id="globalWrapper">
	<div id="column-content">
		<div id="content">
			<p><a name="top" id="top"></a></p>
			<h1 class="firstHeading">Automixer Gain Sharing</h1>
			<div id="bodyContent">
				<p id="siteSub">&#160;<br>
				<img src="Automixer.jpg" alt="" border="0"></p>
				&#160; 
				<p>In addition to the features of a conventional mixer 
				 'Automixers' allow 'hands-free' multi-microphone mixing 
				 without the need for 'manual gain riding' to keep background 
				 noise and feedback under control.</p>
				<p>These objects use an Adaptive Threshold Gain Sharing 
				 technique to control the attenuation in each input channel. 
				 Note that due to this automation, automatic mixers can 
				 use many DSP resources.</p>
				<p>All inputs share the available gain; i.e. an 'open' 
				 microphone will attract the most gain. If more than one 
				 microphone is in use, the gain in the active channels 
				 is shared to give the same overall system gain. When all 
				 inputs are idle, the shared gain keeps all channels slightly 
				 active to avoid 'pumping' of the background noise. Downward 
				 expansion is however available for further reducing the 
				 background noise contribution from idle microphones. Options 
				 are provided to allow the mixer to be expanded not only 
				 within a given device, but also across the network. Aux. 
				 buses can be created and direct channel outputs may be 
				 made available for final mixing elsewhere, or for adding 
				 equalisation or other processing.</p>
				<br>
				
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Inputs_and_Outputs" id="Inputs_and_Outputs"></a></p>
				<h2>Inputs and Outputs</h2>
				<p>The number of inputs can be set from 2 to 48.</p>
				<p>The output is either mono or stereo.</p>
				<p>There is optionally one output for each aux. bus.</p>
				<p>There is optionally one output for each group bus.</p>
				<p>The direct out property produces an output per channel.</p>
				<p>The master option adds a further Mix Input, Chain Input 
				 and Threshold Output.</p>
				<p>The slave option adds a further Mix Input, Chain Input, 
				 Threshold Input and Chain Output.</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Properties" id="Properties"></a></p>
				<h2>Properties</h2>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Number_of_Channels:" id="Number_of_Channels:"></a></p>
				<h4>Number of Channels:</h4>
				<p>The number of input channels can be selected between 
				 2 and 48.</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Stereo:" id="Stereo:"></a></p>
				<h4>Stereo:</h4>
				<p>Set to &quot;Yes&quot; the automixer will have a stereo 
				 pair of outputs, L and R. In Master or Slave mode there 
				 will also be a Left and Right Mix Input</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Number_of_Groups:" id="Number_of_Groups:"></a></p>
				<h4>Number of Groups:</h4>
				<p>Up to 4 group output buses can be selected.</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Number_of_Auxes:" id="Number_of_Auxes:"></a></p>
				<h4>Number of Auxes:</h4>
				<p>Up to 4 aux. output buses can be selected.</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Pan_Law:" id="Pan_Law:"></a></p>
				<h4>Pan Law:</h4>
				<p>The law of the pan controls may be set to either -3.0dB, 
				 -4.5dB or -6.0dB. These figures relate to the attenuation 
				 applied to each channel at the central pan position.</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Master.2FSlave_Status:" id="Master.2FSlave_Status:"></a></p>
				<h4>Master/Slave Status:</h4>
				<p>For expanding the mixer, either for making a larger 
				 mixer within a device, or for splitting a mixer across 
				 more than one device. The control signals are shared using 
				 two special versions of the automixer - Master and Slave.</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Voice_Band_filters:" id="Voice_Band_filters:"></a></p>
				<h4>Voice Band filters:</h4>
				<p>Filtering may be included so that the automixing action 
				 favours frequencies in the human vocal range. This helps 
				 the mixer to distinguish between speech and noise, giving 
				 a voice signal a better chance of 'winning' against a 
				 noise signal on another channel.</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Direct_Outs:" id="Direct_Outs:"></a></p>
				<h4>Direct Outs:</h4>
				<p>In addition to a single mixed output, the individual 
				 automixed channels may be output for further processing 
				 or mixing elsewhere. &#160;These individual outputs are 
				 taken from before the mix but after any processing such 
				 as gain and so on are applied. &#160;Set to Yes if Direct 
				 outputs are required. .</p>
				<div class="editsection" style="float: right; margin-left: 5px;">
					<p>&#160;</p>
				</div>
				<p><a name="Control_Panel" id="Control_Panel"></a></p>
				<h2>Control Panel</h2>
				<p>&#160;<br>
				<img src="Automix_control_panel.jpg" alt="Image:Automix control panel.jpg" title="Image:Automix control panel.jpg" style="border-width: 2px; 
					 border-style: solid; margin-top: 0px; margin-bottom: 0px; 
					 margin-left: 0px; margin-right: 0px;" width="605" height="637" border="2"></p>
				<p>&#160;<span class="hcp1"><br>
				Fader</span> for each input. This controls the level of 
				 the channel's input before the automix logic is applied.</p>
				<p><span class="hcp1">Pan control</span> 
				 control (stereo objects only)</p>
				<p><span class="hcp1">Mute</span> button 
				 for each input.</p>
				<p><span class="hcp1">Polarity</span> button 
				 for each input (for signal inversion)</p>
				<p><span class="hcp1">Gain</span> control 
				 for each output</p>
				<p><span class="hcp1">Solo</span> control 
				 for each input channel for quick identification of signals 
				 and level setting: Allows only 'soloed' channels to be 
				 heard. NOTE: This feature is disabled in any 'master' 
				 or 'slave' automixer.</p>
				<p>! This is a 'solo-in-place' which impacts the main output.</p>
				<p><span class="hcp1">Override</span> button 
				 for each input: Forces this channel to be heard above 
				 all the others. Useful for a chairperson to interrupt 
				 a conference speaker for example. NOTE: Use of this feature 
				 modifies the behavior of the 'On Indicator.'</p>
				<p><span class="hcp1">Auto/Manual button</span> 
				 assigns each channel to operate as either a conventional 
				 mixer channel (Manual) or an automated channel (Auto). 
				 &#160;It should be noted that when a channel is set to 
				 manual it will still contribute to the overall gain attenuation 
				 for the channels which are set to Auto.</p>
				<p><span class="hcp1">Off Gain</span> determines 
				 what maximum attenuation will be applied by the downward 
				 expander to an idle channel. The Off Gain provides some 
				 downward expansion per input, which allows the relative 
				 difference between 'winning' inputs and 'losing' inputs 
				 to be accentuated. This is useful for suppressing low 
				 level 'idle' inputs (i.e. background noise), giving a 
				 larger offset between the louder winning signal (which 
				 we want to hear) and suppressing low level signals (which 
				 we don't want to hear). When this control is set to 0dB, 
				 no downward expansion is applied. The setting of this 
				 control has some effect on the point at which the On indicators 
				 illuminate.</p>
				<p><span class="hcp1">Gain</span> control 
				 for the Main output(s)</p>
				<p><span class="hcp1">Master Mute</span> 
				 button for the Main output(s)</p>
				<p><span class="hcp1">Slope</span> control 
				 determines how aggressive the gain sharing is. Low slope 
				 settings cause the object to behave just like a conventional 
				 mixer. High slope settings cause the inputs to attenuate 
				 more deeply for 'closed' microphones. The fully clockwise 
				 2:1 setting will be appropriate for most applications, 
				 but if you find the action to be too aggressive and do 
				 not want idle microphones to be 'dimmed' as much, then 
				 back this control off slightly.</p>
				<p><span class="hcp1">Speed</span> control 
				 determines how quickly a channel recovers from being open. 
				 Fast (anti-clockwise) settings will be needed if different 
				 speakers are speaking in quick succession since slow settings 
				 would prevent a newly active channel from fading up quickly 
				 enough. If the setting is too fast however, the gain sharing 
				 could 'pump' the gain up and down between spoken words. 
				 A setting somewhere near the centre of the travel will 
				 be found suitable in most cases.</p>
				<p><span class="hcp1">On Indicator</span> 
				 for each input shows when a channel is active. The 'on' 
				 level is related to the setting of the 'off gain' control. 
				 Since the gain sharing algorithm is a linear process, 
				 there is actually no concept of absolute 'on' or 'off'. 
				 Note that only one On indicator is allowed to be 'on' 
				 at a time so that the indicators may be applied to logic 
				 outputs to identify the speaker in automated camera applications. 
				 NOTE: When any channel is placed into 'Override' mode, 
				 the on indicator for that channel will be on as long as 
				 override mode is engaged. The on indicators for non-override 
				 channels will be off.</p>
				<p><span class="hcp1">Aux Masters</span> 
				 level and mute control for each aux bus output (Auxes 
				 are post-fader and post processing)</p>
				<p><span class="hcp1">Group level</span> 
				 level and mute control for each group bus output</p>
				<p><span class="hcp1">Signal Name</span> 
				 shows the name of the input signal</p>
				<h2>&#160;<br>
				Automixer Expansion</h2>
				<p class="hcp2"><span class="hcp3">It 
				 is possible to combine several Automixers together so 
				 that they act as one large Automixer. This makes use of 
				 the Master/Slave Status setting in the Properties Pane 
				 and also makes use of the Threshold and Chain control 
				 signals. These control signals can be passed across devices 
				 using Cobraet, Digital Audio Bus or Digital cards, if 
				 required. Note: these control signals cannot be across 
				 devices using the analogue inputs and outputs.</span></p>
				<p class="hcp2">&#160;</p>
				<p class="hcp2">Connecting two Automixers</p>
				<p class="hcp2"><span class="hcp3">Connect 
				 the Threshold Out of the master to the Threshold In of 
				 the slave, and the Chain Out of the slave to the Chain 
				 In of the master. If you require the outputs of the two 
				 mixers to be combined, connect the Mix Out of the slave 
				 to the Mix In of the master, then use the Mix Out of the 
				 master.</span></p>
				<p>&#160;<img src="Automixers_two.png" alt="Image:Automixers_two.png&lt;/p&gt; &lt;p style=" font-weight:="" title="Image:Automixers_two.png&lt;/p&gt; &lt;p style=" width="666" height="276" border="0"></p>
				<p class="hcp2">Connecting more than two 
				 Automixers</p>
				<p>Create one master and several slaves and connect the 
				 Threshold Out on the master to all the Threshold Ins of 
				 the slaves and 'daisy chain ' the Chain Out of one slave 
				 to the Chain In of the next slave, and so on (in any order) 
				 to the Chain In of the master. If you require the outputs 
				 of all the mixers to be combined, 'daisy chain' the Mix 
				 Out of one slave to the Mix In of the next slave and so 
				 on (in any order) to the Mix In of the master, then use 
				 the Mix Out of the master.</p>
				<p>&#160;<img src="Automixers_four.png" alt="Image:Automixers_four.png&lt;/p&gt; &lt;p&gt;&#160;&lt;span style=" margin-bottom:="" font-weight:="" title="Image:Automixers_four.png&lt;/p&gt; &lt;p&gt;&#160;&lt;span style=" width="830" height="521" border="0"><br>
				&#160;</p>
				<p><span style="margin-bottom: 0; font-weight: bold;">N</span><span class="hcp1">otes on connecting several 
				 Automixers</span></p>
				<p class="hcp4">� The Speed and Slope controls 
				 should be set the same on all linked Automixers for correct 
				 operation.</p>
				<p class="hcp4">� If you require the Aux or 
				 Group outputs of two or more Automixers you will need 
				 to combine them manually using a Summer or Mixer.</p>
				<p style="margin-bottom: 0; font-weight: bold;">Threshold 
				 Bus and Chain control signals</p>
				<p class="hcp4">Combining Automixers is made 
				 possible by distributing a Threshold bus control signal. 
				 This control signal represents the RMS sum of all the 
				 Automixers� input signals. This control signal is required 
				 by every individual Automixer to allow all the Automixers 
				 to act as a composite Automixer.</p>
				<p class="hcp4">Each slave Automixer contributes 
				 to the Threshold bus by summing its local control signal 
				 to the signal received at its Chain In input, and passing 
				 the resultant signal via its Chain Out output to the next 
				 slave Automixer�s Chain In input. These are connected 
				 in a daisy chain fashion until the last slave Automixer�s 
				 Chain Out is connected to the Chain In of the master Automixer.</p>
				<p class="hcp4">The master Automixer then 
				 sums this signal with its local control signal, creating 
				 the resultant Threshold bus. This resultant Threshold 
				 bus is then sent from the master to every one of the slave 
				 Automixers, so that every Automixer receives the same 
				 resultant Threshold bus. This is achieved by connecting 
				 the Threshold Out of the master Automixer to the Threshold 
				 Input of every slave Automixer.</p>
				<p class="hcp4"><span class="hcp1">Notes</span>: 
				 ! This object is capable of raising signal levels beyond 
				 the clipping point, so care should be exercised when using 
				 positive gain values.</p>
			</div>
		</div>
	</div>
</div>
</body>
</html>