{"id":3618,"date":"2014-07-26T11:00:31","date_gmt":"2014-07-26T10:00:31","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=3618"},"modified":"2014-07-28T21:26:20","modified_gmt":"2014-07-28T20:26:20","slug":"robustiano-v0-7","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2014\/07\/26\/robustiano-v0-7\/","title":{"rendered":"Robustiano (V0.7)"},"content":{"rendered":"

Hacked a simple PCB to build the follower to drive the 4P1L as suggested by Rod. I had to play with the LND150 setting resistor (R4) to achieve the 2mA of idle current. I ended up biasing the 4P1L rather hot at about 11.5W\u00a0which exceeds the specs. The Q2 VBE was not possible to measure as the Q2 would oscillate I guess when I place the tester lead on Q1 collector and the voltage seems to drop when I try to measure it. Should have added a ferrite bead:<\/p>\n

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

When measuring distortion against frequency, I was keen to see that the follower provided some\u00a0impact\u00a0in reducing the HF distortion. For example at 20kHz, THD reduced from 0.96% to 0.59% @1W output power and from 7.84% to \u00a03.52%, that is close to half the distortion I had before:<\/p>\n

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

What is nice to see now is the effect of the follower providing sufficient source current to the 4P1L grid. Above 2.5W, the grid current kicks in and we can see how “Robustiano” can deliver 3W at less than 1% until starts to clip about 3.5W:<\/p>\n

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

I found that if I were to reduce the Rf further and therefore increasing the collector current but obviously exceeding the 4P1L power\u00a0dissipation\u00a0too much as collector current was about 45-48mA, the distortion at 20kHz falls significantly. I suspect I should increase the collector current to enable better drive of Q2 due to its Cib (30pF). To keep the current feedback arrangement this could be done by reducing the negative emitter voltage source (V1). Should try this I guess…<\/p>\n

\"20140726-093332-34412311.jpg\"<\/a><\/p>\n

 <\/p>\n

Cheers<\/p>\n

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

Hacked a simple PCB to build the follower to drive the 4P1L as suggested by Rod. I had to play with the LND150 setting resistor (R4) to achieve the 2mA of idle current. I ended up biasing the 4P1L rather hot at about 11.5W\u00a0which exceeds the specs. The Q2 VBE was not possible to measure … Continue reading “Robustiano (V0.7)”<\/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":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},"jetpack_post_was_ever_published":false},"categories":[12,153,154,158,67,5],"tags":[782,622,618,617,322,616,352],"class_list":["post-3618","post","type-post","status-publish","format-standard","hentry","category-dht-valves","category-driver","category-output-stage","category-se-designs","category-thd","category-valves","tag-4p1l","tag-4p1l-robustiano","tag-4p1l-schade","tag-4p1l-schade-feedback","tag-4p1l-se","tag-robustiano","tag-schade-feedback"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-Wm","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/3618","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=3618"}],"version-history":[{"count":7,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/3618\/revisions"}],"predecessor-version":[{"id":3640,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/3618\/revisions\/3640"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=3618"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=3618"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=3618"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}