{"id":245,"date":"2012-04-10T20:48:06","date_gmt":"2012-04-10T20:48:06","guid":{"rendered":"http:\/\/stompville.co.uk\/?p=245"},"modified":"2020-10-11T15:24:07","modified_gmt":"2020-10-11T15:24:07","slug":"altoids-piezo-di-revisited","status":"publish","type":"post","link":"https:\/\/stompville.co.uk\/?p=245","title":{"rendered":"Altoids piezo DI revisited"},"content":{"rendered":"<p>I&#8217;ve had some interest in and feedback for my <a title=\"Altoids piezo DI box\" href=\"https:\/\/stompville.co.uk\/?p=176\">Altoids Piezo DI box<\/a> and I have revised the design sufficiently to warrant a new post.\u00a0 The new design has the following changes from the previous version:<\/p>\n<ul>\n<li>1\/4&#8243; jacks on input and output<\/li>\n<li>Low-voltage monitor (<a title=\"Low-battery monitor with TC54 voltage detector\" href=\"https:\/\/stompville.co.uk\/?p=200\">TC54<\/a>) on the battery supply<\/li>\n<li>Higher voltage zener (33V)<\/li>\n<li>Increase R7 &amp; R8 to 1M0 (or eliminate them entirely)<\/li>\n<li>Asymmetric bias voltage<\/li>\n<li>Unity gain op-amp circuit<\/li>\n<li>Reduce C4 from 470nF to 100nF<\/li>\n<\/ul>\n<p>These changes have been made to reduce power consumption, free-up space on the PCB and reduce cost.<\/p>\n<p>Here&#8217;s the revised schematic:<\/p>\n<p><a href=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/122SV.png\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-large wp-image-246\" title=\"122SV\" src=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/122SV-1024x725.png\" alt=\"Altoids Piezo DI revised schematic\" width=\"595\" height=\"421\" srcset=\"https:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/122SV-1024x725.png 1024w, https:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/122SV-300x213.png 300w, https:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/122SV.png 1200w\" sizes=\"(max-width: 595px) 100vw, 595px\" \/><\/a><\/p>\n<p>And here&#8217;s a photo of the prototype PCB:<\/p>\n<p style=\"text-align: center;\"><a href=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/P124SV.jpg\" target=\"_blank\" rel=\"noopener noreferrer\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-247\" title=\"P124SV\" src=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/P124SV.jpg\" alt=\"Altoids Piezo DI PCB assembly\" width=\"302\" height=\"248\" srcset=\"https:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/P124SV.jpg 900w, https:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/P124SV-300x246.jpg 300w\" sizes=\"(max-width: 302px) 100vw, 302px\" \/><\/a><\/p>\n<p style=\"text-align: left;\">I had to ditch the switch-with-integrated-LED because it took up too much real estate on the PCB.\u00a0 Also, I have specified Cliff S1 style jack sockets because they take up less space on the PCB and are lower-profile than standard sockets.\u00a0 The Altoids lid fits better with the lower-profile sockets.<\/p>\n<p style=\"text-align: left;\">If you can get Cliff sockets with a <a title=\"http:\/\/www.cliffuk.co.uk\/products\/jacksockets\/S1.pdf\" href=\"https:\/\/www.cliffuk.co.uk\/products\/jacksockets\/S1.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">&#8220;special nose&#8221;<\/a> (half threaded) all the better. You can buy them from the Stompville shop <a title=\"stompville.co.uk\/shop\/7-cliff-s1bbb-14-stereo-jack.html\" href=\"http:\/\/stompville.co.uk\/shop\/7-cliff-s1bbb-14-stereo-jack.html\" target=\"_blank\" rel=\"noopener noreferrer\">here<\/a>.<\/p>\n<p style=\"text-align: left;\">Here&#8217;s the PCB layouts (the foil is at 600 dpi):<\/p>\n<p style=\"text-align: left;\"><a href=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/P125SV.jpg\" target=\"_blank\" rel=\"noopener noreferrer\"><img loading=\"lazy\" decoding=\"async\" style=\"border: 2px solid black;\" title=\"P125SV\" src=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/P125SV-150x150.jpg\" alt=\"Overlay\" width=\"150\" height=\"150\" \/><\/a> \u00a0 \u00a0 <a href=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/P126SV.gif\" target=\"_blank\" rel=\"noopener noreferrer\"><img loading=\"lazy\" decoding=\"async\" style=\"border: 2px solid black;\" title=\"P126SV\" src=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/04\/P126SV-150x150.gif\" alt=\"PCB Foil\" width=\"150\" height=\"150\" \/><\/a><\/p>\n<p style=\"text-align: left;\">As with the previous design, the input socket is the lower of the two.\u00a0 R16 and R17 set up the TC54 to turn the LED on when the battery voltage falls to about 7.3V.\u00a0 When phantom powered (from 48V), the voltage between pin 8 and pin 4 of the op-amp should be a little less than 30V.\u00a0 All 1\/8W resistors except for R13.<\/p>\n<p style=\"text-align: left;\">Note that Q1 and the op-amp require different bias voltages.\u00a0 This is because the source resistor in Q2 raises the operating point of Q1.\u00a0 R14 and R15 have been selected as a compromise to reduce component count.\u00a0 You should find that the d.c. voltage at the source of Q1 is a little higher than 1\/2Vcc and the voltage at pin 5 of the op-amp (both measured with respect to ground) is a little lower than 1\/2Vcc.\u00a0 <img loading=\"lazy\" decoding=\"async\" title=\"svfavicon.png\" src=\"http:\/\/stompville.co.uk\/wp-content\/uploads\/2012\/02\/svfavicon.png\" alt=\"\" width=\"16\" height=\"16\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>I&#8217;ve had some interest in and feedback for my Altoids Piezo DI box and I have revised the design sufficiently to warrant a new post.\u00a0 The new design has the following changes from the previous version: 1\/4&#8243; jacks on input and output Low-voltage monitor (TC54) on the battery supply Higher voltage zener (33V) Increase R7\u2026 <span class=\"read-more\"><a href=\"https:\/\/stompville.co.uk\/?p=245\">Read More &raquo;<\/a><\/span><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,7],"tags":[],"_links":{"self":[{"href":"https:\/\/stompville.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/245"}],"collection":[{"href":"https:\/\/stompville.co.uk\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/stompville.co.uk\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/stompville.co.uk\/index.php?rest_route=\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/stompville.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=245"}],"version-history":[{"count":4,"href":"https:\/\/stompville.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/245\/revisions"}],"predecessor-version":[{"id":1436,"href":"https:\/\/stompville.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/245\/revisions\/1436"}],"wp:attachment":[{"href":"https:\/\/stompville.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=245"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/stompville.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=245"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/stompville.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=245"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}