{"id":7797,"date":"2019-03-03T17:43:52","date_gmt":"2019-03-03T17:43:52","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=7797"},"modified":"2019-03-03T17:44:51","modified_gmt":"2019-03-03T17:44:51","slug":"47-push-pull-with-local-feedback","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2019\/03\/03\/47-push-pull-with-local-feedback\/","title":{"rendered":"47 Push-Pull with local feedback"},"content":{"rendered":"

This design is inspired on the great work from Gary Pimm. The 47<\/a> is a sterling directly heated pentode and worth using it. I have several on my stash, including some good globe versions.<\/p>\n

The following topology is well known. \u00a0The push-pull output stage has local feedback (a.k.a. “A la Schade”) between anode and grid. Obviously the drivers are pentodes. Subtle difference is that I added a source follower in between grids to provide negative bias and grid current drive.<\/p>\n

The drivers are based out of the beloved 6J49P-DR. Need to finalise it. The stage can do 8W at less than 0.6% THD with an OPT with Zaa 8K\u03a9.<\/p>\n

I prototyped a new PCB with a simple circuit to provide Screen voltage regulation based on a VR. Quite handy in a circuit like this. Let’s see how it turns out.<\/p>\n

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

Looking at my notes and archive from 4-5 years ago, here are the “Schaded” anode curves:<\/p>\n

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

Quite a lot of FB applied here to get the anode resistance down to 800-900\u03a9.<\/p>\n

This will make a nice sounding amplifier!<\/p>\n","protected":false},"excerpt":{"rendered":"

This design is inspired on the great work from Gary Pimm. The 47 is a sterling directly heated pentode and worth using it. I have several on my stash, including some good globe versions.<\/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":[5],"tags":[92,1214,1212,827,1213],"class_list":["post-7797","post","type-post","status-publish","format-standard","hentry","category-valves","tag-92","tag-47-pp-amp","tag-47-push-pull","tag-schade","tag-schade-47"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-21L","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7797","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=7797"}],"version-history":[{"count":2,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7797\/revisions"}],"predecessor-version":[{"id":7802,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7797\/revisions\/7802"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=7797"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=7797"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=7797"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}