{"action":"created","issue":{"url":"https://api.github.com/repos/AppleWin/AppleWin/issues/275","labels_url":"https://api.github.com/repos/AppleWin/AppleWin/issues/275/labels{/name}","comments_url":"https://api.github.com/repos/AppleWin/AppleWin/issues/275/comments","events_url":"https://api.github.com/repos/AppleWin/AppleWin/issues/275/events","html_url":"https://github.com/AppleWin/AppleWin/pull/275","id":67877173,"number":275,"title":"Speaker output DC blocking","user":{"login":"rmacri","id":11404102,"avatar_url":"https://avatars.githubusercontent.com/u/11404102?v=3","gravatar_id":"","url":"https://api.github.com/users/rmacri","html_url":"https://github.com/rmacri","followers_url":"https://api.github.com/users/rmacri/followers","following_url":"https://api.github.com/users/rmacri/following{/other_user}","gists_url":"https://api.github.com/users/rmacri/gists{/gist_id}","starred_url":"https://api.github.com/users/rmacri/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rmacri/subscriptions","organizations_url":"https://api.github.com/users/rmacri/orgs","repos_url":"https://api.github.com/users/rmacri/repos","events_url":"https://api.github.com/users/rmacri/events{/privacy}","received_events_url":"https://api.github.com/users/rmacri/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":7,"created_at":"2015-04-12T06:14:15Z","updated_at":"2015-05-25T17:00:28Z","closed_at":null,"pull_request":{"url":"https://api.github.com/repos/AppleWin/AppleWin/pulls/275","html_url":"https://github.com/AppleWin/AppleWin/pull/275","diff_url":"https://github.com/AppleWin/AppleWin/pull/275.diff","patch_url":"https://github.com/AppleWin/AppleWin/pull/275.patch"},"body":"The Apple speaker code correctly drives the soundcard at  +32767/-32768 for its two states, leaving the sound card with a large DC offset. I've noticed this cause loud clicks when my system is busy and AppleWin underruns its audio, as well as clicks when I change volume on the soundcard, both due to the DC offset. I guess my card is DC coupled. Recently I also noticed my connected Yamaha amp does not like the DC offset  (eg: affects sound playing in Winamp). \r\nSo I've implemented a simple DC blocking integrator/capacitor. This has no affect on regular Apple audio as it adjustments are small and operate over the order of a second. Comments have detailed explanation."},"comment":{"url":"https://api.github.com/repos/AppleWin/AppleWin/issues/comments/105270604","html_url":"https://github.com/AppleWin/AppleWin/pull/275#issuecomment-105270604","issue_url":"https://api.github.com/repos/AppleWin/AppleWin/issues/275","id":105270604,"user":{"login":"rmacri","id":11404102,"avatar_url":"https://avatars.githubusercontent.com/u/11404102?v=3","gravatar_id":"","url":"https://api.github.com/users/rmacri","html_url":"https://github.com/rmacri","followers_url":"https://api.github.com/users/rmacri/followers","following_url":"https://api.github.com/users/rmacri/following{/other_user}","gists_url":"https://api.github.com/users/rmacri/gists{/gist_id}","starred_url":"https://api.github.com/users/rmacri/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rmacri/subscriptions","organizations_url":"https://api.github.com/users/rmacri/orgs","repos_url":"https://api.github.com/users/rmacri/repos","events_url":"https://api.github.com/users/rmacri/events{/privacy}","received_events_url":"https://api.github.com/users/rmacri/received_events","type":"User","site_admin":false},"created_at":"2015-05-25T17:00:28Z","updated_at":"2015-05-25T17:00:28Z","body":"Just pushed a much better DC filter implementation using the attenuator \napproach, much simpler and does not affect any playing audio. I dont \nthink I have to update the pull request do I?\nRegards\n\nOn 20/05/2015 6:16 AM, TomCh wrote:\n> FYI, one positive difference with this patch vs the latest release of\n> AppleWin 1.25.0.4, is that with the current release you get a click when\n> stopping at a Visual Studio debugger breakpoint (and another click on a\n> restart). But with the patch there's silence.\n>\n> EG. Break to the AppleSoft prompt and wait 1 sec to let the filter\n> accumulate to 0x7FFF (ie. so that the DirectSound ring-buffer is just\n> outputting 0x0000's).\n>\n> —\n> Reply to this email directly or view it on GitHub\n> <https://github.com/AppleWin/AppleWin/pull/275#issuecomment-103669287>.\n>\n\n"}}