{"action":"created","issue":{"url":"https://api.github.com/repos/TomWhitwell/RadioMusic/issues/77","labels_url":"https://api.github.com/repos/TomWhitwell/RadioMusic/issues/77/labels{/name}","comments_url":"https://api.github.com/repos/TomWhitwell/RadioMusic/issues/77/comments","events_url":"https://api.github.com/repos/TomWhitwell/RadioMusic/issues/77/events","html_url":"https://github.com/TomWhitwell/RadioMusic/issues/77","id":104320109,"number":77,"title":"DC offset issue.","user":{"login":"phidelity","id":4985023,"avatar_url":"https://avatars.githubusercontent.com/u/4985023?v=3","gravatar_id":"","url":"https://api.github.com/users/phidelity","html_url":"https://github.com/phidelity","followers_url":"https://api.github.com/users/phidelity/followers","following_url":"https://api.github.com/users/phidelity/following{/other_user}","gists_url":"https://api.github.com/users/phidelity/gists{/gist_id}","starred_url":"https://api.github.com/users/phidelity/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/phidelity/subscriptions","organizations_url":"https://api.github.com/users/phidelity/orgs","repos_url":"https://api.github.com/users/phidelity/repos","events_url":"https://api.github.com/users/phidelity/events{/privacy}","received_events_url":"https://api.github.com/users/phidelity/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":1,"created_at":"2015-09-01T17:48:38Z","updated_at":"2015-09-01T20:16:16Z","closed_at":null,"body":"I am new to github and issue/bug reporting so if I'm doing this entirely wrong, please bear with me and point me in the right direction.\r\n\r\nI've built a batch of Radio Musics and I'm pretty consistently getting the same problem with close to 10 of them, which means the error is possibly in my builds with a wrong component (looked and tested and everything seems to be in the right place, orientation & values) or perhaps a bad batch or fried 78L05 regulators or some other component. \r\n\r\nThe issue is this: when looking at the output on a o'Jones scope and the amplifier trimpot all the way down - the volume has a DC offset of a volt or two, as I turn the amplifier trimpot up this increases the DC offset until its above what eurorack can handle ( ~3-4 volts above 0v ) and the audio clips until it disappears.\r\n\r\nIf I take this same signal into a 4ms SISM and apply a manual negative DC offset adjusted to 0v the amplifier works perfectly. Does this give you any clue where I should begin trouble shooting? Is there a specific circuit which handles this aspect of the amplification?\r\n\r\nthanks!\r\nkris"},"comment":{"url":"https://api.github.com/repos/TomWhitwell/RadioMusic/issues/comments/136847691","html_url":"https://github.com/TomWhitwell/RadioMusic/issues/77#issuecomment-136847691","issue_url":"https://api.github.com/repos/TomWhitwell/RadioMusic/issues/77","id":136847691,"user":{"login":"TomWhitwell","id":1890544,"avatar_url":"https://avatars.githubusercontent.com/u/1890544?v=3","gravatar_id":"","url":"https://api.github.com/users/TomWhitwell","html_url":"https://github.com/TomWhitwell","followers_url":"https://api.github.com/users/TomWhitwell/followers","following_url":"https://api.github.com/users/TomWhitwell/following{/other_user}","gists_url":"https://api.github.com/users/TomWhitwell/gists{/gist_id}","starred_url":"https://api.github.com/users/TomWhitwell/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/TomWhitwell/subscriptions","organizations_url":"https://api.github.com/users/TomWhitwell/orgs","repos_url":"https://api.github.com/users/TomWhitwell/repos","events_url":"https://api.github.com/users/TomWhitwell/events{/privacy}","received_events_url":"https://api.github.com/users/TomWhitwell/received_events","type":"User","site_admin":false},"created_at":"2015-09-01T20:16:16Z","updated_at":"2015-09-01T20:16:16Z","body":"The Teensy DAC has an offset of 2-3 volts, which is blocked by C2 and C3. If you have got substantially wrong values there (maybe 100p rather than 100n?) or they are shortcircuited somehow, that might explain it? "}}