{"id":2556,"date":"2013-10-19T18:27:05","date_gmt":"2013-10-19T17:27:05","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=2556"},"modified":"2013-10-19T18:31:35","modified_gmt":"2013-10-19T17:31:35","slug":"jfet-riaa-preamp-build-part-ii","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2013\/10\/19\/jfet-riaa-preamp-build-part-ii\/","title":{"rendered":"JFET RIAA Preamp Build (Part II)"},"content":{"rendered":"

I made the following changes to the RIAA stage to improve its accuracy:<\/p>\n

    \n
  1. \u00a0Measured all caps<\/li>\n
  2. Adjusted 75uS network to compensate for the capacitor variance and the cascode output impedance<\/li>\n
  3. Adjusted 318uS and 3180uS networks to compensate for the capacitor variance<\/li>\n<\/ol>\n

    All resistors were adjusted with a pair of 0.1% SMD resistors to avoid series connection to reduce noise level.<\/p>\n

    As shown below, the response is really good matching at less than 1% for frequencies above 50Hz. the error at low frequency is due to the rumble low pass filter, the hum and the soundcard LF response which introduce a slight\u00a0distortion at very low frequency\u00a0in the MLS measurement:<\/p>\n\n\n\n<\/colgroup>\n\n\n\n\n\n\n
    Frequency (Hz)<\/strong><\/td>\nTest (dB)<\/strong><\/td>\nRIAA (dB)<\/strong><\/td>\nError<\/strong><\/td>\n<\/tr>\n
    \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 20<\/td>\n18.80<\/td>\n19.27<\/td>\n2.44%<\/td>\n<\/tr>\n
    \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 100<\/td>\n13.00<\/td>\n13.09<\/td>\n0.69%<\/td>\n<\/tr>\n
    \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 1,000<\/td>\n0.00<\/td>\n0.00<\/td>\n0.00%<\/td>\n<\/tr>\n
    \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 10,000<\/td>\n-13.70<\/td>\n-13.73<\/td>\n0.22%<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    \"jfet<\/a><\/p>\n

    \"RIAA<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    I made the following changes to the RIAA stage to improve its accuracy: \u00a0Measured all caps Adjusted 75uS network to compensate for the capacitor variance and the cascode output impedance Adjusted 318uS and 3180uS networks to compensate for the capacitor variance All resistors were adjusted with a pair of 0.1% SMD resistors to avoid series … Continue reading “JFET RIAA Preamp Build (Part II)”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[156,448,5],"tags":[450,451,453,789],"class_list":["post-2556","post","type-post","status-publish","format-standard","hentry","category-pre-amplifier-valves","category-riaa-stages","category-valves","tag-jfet-riaa","tag-jfet-riaa-shunt-cascode","tag-phono-preamplifier","tag-riaa"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-Fe","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/2556","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/comments?post=2556"}],"version-history":[{"count":5,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/2556\/revisions"}],"predecessor-version":[{"id":2562,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/2556\/revisions\/2562"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=2556"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=2556"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=2556"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}