{"id":8867,"date":"2020-09-27T16:36:33","date_gmt":"2020-09-27T15:36:33","guid":{"rendered":"https:\/\/www.bartola.co.uk\/valves\/?p=8867"},"modified":"2020-09-27T16:36:33","modified_gmt":"2020-09-27T15:36:33","slug":"rl12p35-se-amp-part-i","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2020\/09\/27\/rl12p35-se-amp-part-i\/","title":{"rendered":"RL12P35 SE Amp – part I"},"content":{"rendered":"

I have plenty of these<\/a> German WWII pentodes. I’ve been saving them for a few projects. Quite likely for a push-pull amp given the OB speaker project I’m cooking. Either way, I have a nice set of CFB SE as well as PP OPTs from Toroidy custom made. They are very good transformers.<\/p>\n

So, if you want a simple SE amplifier that can do 8W, here is a good contraption to go after:<\/p>\n

\"\"<\/a>The OPT has a couple of feedback windings to provide 10% CFB. I set the valve rather hot, I know. Probably a tad too much. Should be 35W maximum. You can do GU-50 here and get more power, cheap and easy.<\/p>\n

The driver is a gem. The EF184 is a superb pentode when triode-strapped. Can do very well on the same levels of a D3a and is (yet) somehow still cheaper. Cathode degeneration plays well and easy here in the hybrid mu-follower.<\/p>\n

Some people would say: “pentode and cathode feedback, arghh!!”. Trust me, good path down this way when feedback is local of course.<\/p>\n

Although the stage can do 8W and THD will jump up to 2.9% is nice to see the triode-like harmonic distribution. Here is the view at 1W:<\/p>\n

\"\"<\/a>If you push the output stage to its limits, you will get this:<\/p>\n

\"\"<\/a>
RLP1235 @ 8W output<\/figcaption><\/figure>\n

Bandwidth is over 65kHz. A simple and nice amplifier. With different arrangements on feedback like plate to grid with cathode driven via a PMOS and increasing the FB ratio to 20%, you can get less than 1% at 7W output. But that’s a rather more complex amplifier. This is simpler.<\/p>\n

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

I have plenty of these German WWII pentodes. I’ve been saving them for a few projects. Quite likely for a push-pull amp given the OB speaker project I’m cooking. Either way, I have a nice set of CFB SE as well as PP OPTs from Toroidy custom made. They are very good transformers. So, if … Continue reading “RL12P35 SE Amp – part I”<\/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":[158,5],"tags":[1374,1376,1375,96,1377,913],"class_list":["post-8867","post","type-post","status-publish","format-standard","hentry","category-se-designs","category-valves","tag-cathode-feedback-se-ampliifier","tag-cfb","tag-cfb-se","tag-ef184","tag-ef184-triode","tag-rl12p35"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-2j1","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/8867","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=8867"}],"version-history":[{"count":1,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/8867\/revisions"}],"predecessor-version":[{"id":8871,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/8867\/revisions\/8871"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=8867"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=8867"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=8867"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}