{"id":7499,"date":"2018-07-29T21:00:39","date_gmt":"2018-07-29T20:00:39","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=7499"},"modified":"2018-07-29T21:00:39","modified_gmt":"2018-07-29T20:00:39","slug":"spud-push-pull-amplifier","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2018\/07\/29\/spud-push-pull-amplifier\/","title":{"rendered":"Spud Push-Pull Amplifier"},"content":{"rendered":"

I devoted the majority of my audio life to single-ended DHT amplifiers. I don’t regret the path, however, I do not want a polarised perspective on amplifiers. I do like very much a good push-pull amp, though. Over time, I stumble across poor implementations or excessive use of gNFB. Local feedback (lFB) designs well implemented are music to my ears.<\/p>\n

I played around with SPUD amps over the years, with happy results. One of them I loved over the breadboard is the 6e5p in push-pull. I will definitely build a definitive version of it. Here is the concept overall:\"\"<\/a><\/p>\n

The input transformers is step up. It will need 1:4+4 ideally. My friend Dorin from DVB Transformers has a great device<\/a> which I reviewed before and would be ideal for this amplifier. To simplify the power supplies, I used only one, which provides a bit of a strain into the source followers SF1 and SF2. If you have a good driver, you can omit them, I wouldn’t. They take care of the miller capacitance which is worsened by the step up transformer. It’s just a pair of PCBs, not big deal. RK1 is an arrangement with a pot to balance the bias. C1 is in ultrapath. I used an Oil 40uF one. T1 was a Lundahl 8K8:8\u03a9 PP OPT.<\/p>\n

The CCS provides a stable bias current into RBIAS1 which sets the bias voltage.<\/p>\n

Here is the operating point I used:<\/p>\n

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

The 6e5p is biased at about 40-43mA and 240V. It needs 5V bias so a cathode resistor of 58\u03a9 should do. For 4W output in A1, you need 4Vrms, which only with a 1:2+2 step up should do. You can get about 5W in A2 or a tad more.<\/p>\n

I loved the sound of the 6e5p as output stage (as much as I do as driver).<\/p>\n

There are multiple variances to explore indeed<\/p>\n

I have a pair of Toroidy PP OPTs with CFB, so would be interested in running them in tetrode instead.<\/p>\n

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

I devoted the majority of my audio life to single-ended DHT amplifiers. I don’t regret the path, however, I do not want a polarised perspective on amplifiers. I do like very much a good push-pull amp, though. Over time, I stumble across poor implementations or excessive use of gNFB. Local feedback (lFB) designs well implemented … Continue reading “Spud Push-Pull Amplifier”<\/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":[5],"tags":[29,1154,132,1155,962,1156],"class_list":["post-7499","post","type-post","status-publish","format-standard","hentry","category-valves","tag-6e5p","tag-6e5p-push-pull","tag-lundahl","tag-push-pull-amplifier","tag-spud","tag-toroidy"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1WX","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7499","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=7499"}],"version-history":[{"count":1,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7499\/revisions"}],"predecessor-version":[{"id":7502,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7499\/revisions\/7502"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=7499"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=7499"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=7499"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}