{"id":2,"date":"2013-03-22T12:26:25","date_gmt":"2013-03-22T12:26:25","guid":{"rendered":"http:\/\/www.audioemc.co.uk\/?page_id=2"},"modified":"2013-04-10T13:01:03","modified_gmt":"2013-04-10T13:01:03","slug":"sample-page","status":"publish","type":"page","link":"http:\/\/www.audioemc.co.uk\/?page_id=2","title":{"rendered":"Hum, buzz, clicks, razz, &#038; cell phone dialling noise"},"content":{"rendered":"<p>The important thing to remember is that hum, buzz, or any other form of unwanted noise can only become a problem if the component or circuit design allows the noise current to be injected into it\u2019s internal circuit conductors. Unfortunately, rather a lot of audio equipment is designed such that electromagnetic interference is directly injected into the internal circuit<em> ground<\/em>.<\/p>\n<div id=\"attachment_39\" style=\"width: 310px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.audioemc.co.uk\/wp-content\/uploads\/2013\/03\/pin-1-problem-e1364080440803.jpg\"><img aria-describedby=\"caption-attachment-39\" loading=\"lazy\" class=\"size-medium wp-image-39\" alt=\"Fig 1: The pin 1 problem\" src=\"http:\/\/www.audioemc.co.uk\/wp-content\/uploads\/2013\/03\/pin-1-problem-300x158.jpg\" width=\"300\" height=\"158\" \/><\/a><p id=\"caption-attachment-39\" class=\"wp-caption-text\">Fig 1: The pin 1 problem<\/p><\/div>\n<p>Connecting the cable shield conductor directly to the internal circuit ground creates TWO\u00a0separate\u00a0&#8220;ground loops&#8221; that WILL inject noise\/interference into the internal circuit. Noise &amp; interference will also be coupled to the power supply. The power supply will circulate the noise to all parts of the internal electronics. The internal electronic circuits will demodulate (convert) the interference into audible signals.<\/p>\n<p>Similarly &#8211; if a circuit is producing electromagnetic noise &#8211; an audio signal passing through the system will\u00a0<em>modulate<\/em> the interference, and the noise will be radiated by the output &amp; input cables (fig 2).<\/p>\n<div id=\"attachment_52\" style=\"width: 310px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.audioemc.co.uk\/wp-content\/uploads\/2013\/03\/demod-1.jpg\"><img aria-describedby=\"caption-attachment-52\" loading=\"lazy\" class=\"size-medium wp-image-52\" alt=\"Fig 2: Result of demodulation in audio output\" src=\"http:\/\/www.audioemc.co.uk\/wp-content\/uploads\/2013\/03\/demod-1-300x185.jpg\" width=\"300\" height=\"185\" srcset=\"http:\/\/www.audioemc.co.uk\/wp-content\/uploads\/2013\/03\/demod-1-300x185.jpg 300w, http:\/\/www.audioemc.co.uk\/wp-content\/uploads\/2013\/03\/demod-1-1024x632.jpg 1024w, http:\/\/www.audioemc.co.uk\/wp-content\/uploads\/2013\/03\/demod-1-624x385.jpg 624w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><p id=\"caption-attachment-52\" class=\"wp-caption-text\">Fig 2: Result of demodulation in audio output<\/p><\/div>\n<p>We call this <i>reciprocity:<\/i><\/p>\n<p>A conductive structure (eg. Cable, printed circuit board trace) that has a certain antenna behaviour when it picks up an EM wave\u00a0 and produces currents and voltages in a circuit\u00a0\u2013 is exactly the same antenna behaviour as with an emitter of EM waves when currents and voltages are made to occur in a circuit designed to receive or transmit such EM waves.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The important thing to remember is that hum, buzz, or any other form of unwanted noise can only become a problem if the component or circuit design allows the noise current to be injected into it\u2019s internal circuit conductors. Unfortunately, rather a lot of audio equipment is designed such that electromagnetic interference is directly injected [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":94,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=\/wp\/v2\/pages\/2"}],"collection":[{"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2"}],"version-history":[{"count":22,"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=\/wp\/v2\/pages\/2\/revisions"}],"predecessor-version":[{"id":95,"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=\/wp\/v2\/pages\/2\/revisions\/95"}],"up":[{"embeddable":true,"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=\/wp\/v2\/pages\/94"}],"wp:attachment":[{"href":"http:\/\/www.audioemc.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}