{"id":5750,"date":"2016-09-25T21:41:57","date_gmt":"2016-09-25T20:41:57","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=5750"},"modified":"2016-09-25T21:43:51","modified_gmt":"2016-09-25T20:43:51","slug":"building-gyrator-boards","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2016\/09\/25\/building-gyrator-boards\/","title":{"rendered":"Building gyrator boards"},"content":{"rendered":"

I’ve been on some business travel so haven’t had much time to work on stuff, however I did get a set of gyrator boards<\/a> for a friend and a customer:<\/p>\n

    \n
  1. BF862 configured for 4P1L preamp<\/li>\n
  2. 2SK170 configured for 01a preamp<\/a><\/li>\n<\/ol>\n

    4P1L preamp with BF862 gyrator<\/h1>\n

    Many have asked me about this preamp with gyrator load. Here is the latest implementation which I preferred most in terms of sound. The mu resistor is 470\u03a9 which is a nice compromise between BF862 transconductance and distortion. I adjusted it on test. I use a 100nF for C1 so R6 is 10M\u03a9. R4 can be either 300K\u03a9, 330K\u03a9 or even 390K\u03a9. Difference would be only on the voltage range for the CCS. I found running it at 25mA to be perfectly fine, some BF862 can even do J310. I prefer this SMD compared to the J310. It performs much better even at high frequency:<\/p>\n

    \"4p1l-preamp-gen1b-gyrator-pcb-detailed\"<\/a><\/p>\n

     <\/p>\n

    \"4P1L<\/a>
    4P1L gyrator boards<\/figcaption><\/figure>I did some measurements recently and you can see the results here<\/a>:<\/p>\n

    \"4P1L<\/a><\/p>\n

    Back to the 01a Preamp<\/h1>\n

    The finished boards looked like this:<\/p>\n

    \"01a<\/a>
    01a Gyrator boards ready for customer<\/figcaption><\/figure> They have Kiwame resistors for the 1K5\u03a9 Mu resistor, 2SK170, DN2540 and a Mundorf Mcap EVO Aluminium 100nF\/650V 5% for C1.<\/p>\n

    Here is a quick measurement with a lovely UV201a (circa 1922-1924) with brass base:<\/p>\n

    \"01a-denis-fr-test-01\"<\/a><\/p>\n

    The FR is not as great as the BF862 with 4P1L, however it reaches out to 100kHz which is fantastic compared to other preamps using different loads.<\/p>\n

    Here is the harmonic profile for a 2Vrms signal showing the low distortion and the cadence of harmonics characteristic of this valve:
    \n    \"01a-denis-tests-01\"<\/a><\/p>\n

     <\/p>\n

    <\/div>\n","protected":false},"excerpt":{"rendered":"

    I’ve been on some business travel so haven’t had much time to work on stuff, however I did get a set of gyrator boards for a friend and a customer: BF862 configured for 4P1L preamp 2SK170 configured for 01a preamp 4P1L preamp with BF862 gyrator Many have asked me about this preamp with gyrator load. … Continue reading “Building gyrator boards”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":true,"_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},"jetpack_post_was_ever_published":false},"categories":[12,911,156],"tags":[10,249,853,697,782,111,903,777,6,186,72,44,937,938],"class_list":["post-5750","post","type-post","status-publish","format-standard","hentry","category-dht-valves","category-gyrator-pcb","category-pre-amplifier-valves","tag-01a","tag-01a-dht","tag-01a-gyrator","tag-2sk170","tag-4p1l","tag-4p1l-pre-amplifier","tag-bartola-gyrator-pcb","tag-bf862","tag-dht","tag-dht-preamp","tag-dn2540","tag-gyrator","tag-kiwame","tag-uv201a"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1uK","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5750","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=5750"}],"version-history":[{"count":3,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5750\/revisions"}],"predecessor-version":[{"id":5758,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5750\/revisions\/5758"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=5750"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=5750"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=5750"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}