{"id":5553,"date":"2016-05-08T20:12:47","date_gmt":"2016-05-08T19:12:47","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=5553"},"modified":"2016-05-12T20:21:46","modified_gmt":"2016-05-12T19:21:46","slug":"4p1l-preamp","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2016\/05\/08\/4p1l-preamp\/","title":{"rendered":"Gyrator Test Mule: 4P1L Preamp"},"content":{"rendered":"
\"4P1L<\/a>
4P1L gyrator test mule<\/figcaption><\/figure>\n

It’s always great to come back and revisit a great design. The 4P1L preamp performs flawlessly so I tweaked the gyrator board<\/a> to see how it worked with the BF862 FET. The result is great, it sounds as good as it measures:<\/p>\n

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

The 4P1L is biased to 150V\/25mA which is the maximum current that the BF862 can do (IDSS max). You can see that the frequency response is flat up to 1.5MHz. The LF response of my test mule is affected by the AC coupling of the measuring gear. However it should be around 5-10Hz.<\/p>\n

The distortion of low-level signals is really good:<\/p>\n

\"THD<\/a>
THD @ 4Vrms<\/figcaption><\/figure>\n

Predominantly H2, it’s very nice to see THD<0.015% for a 4Vrms output. The load is 100K\u03a9 which is the typical input impedance of an amplifier (with exception of solid state gear)<\/p>\n

This low distortion manifests across the entire audio band (ignore the THD below 20Hz which is a byproduct of my testing gear):<\/p>\n

\"THD<\/a>
THD version frequency @ 4Vrms<\/figcaption><\/figure>\n

The nice thing to see also, it’s how well the 4P1L can drive larger voltage swings:<\/p>\n

\"4P1L<\/a>
4P1L THD @ 10Vrms<\/figcaption><\/figure>\n

We can see H4 popping up, however odd harmonics are lower (H5 in fact is higher than H3). THD at 10Vrms is still below 0.03%!<\/p>\n

 <\/p>\n

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

It’s always great to come back and revisit a great design. The 4P1L preamp performs flawlessly so I tweaked the gyrator board to see how it worked with the BF862 FET. The result is great, it sounds as good as it measures: The 4P1L is biased to 150V\/25mA which is the maximum current that the … Continue reading “Gyrator Test Mule: 4P1L Preamp”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_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}},"categories":[835,911,156],"tags":[782,537,597,864,903,44,875],"class_list":["post-5553","post","type-post","status-publish","format-standard","hentry","category-4p1l-pse-amp","category-gyrator-pcb","category-pre-amplifier-valves","tag-4p1l","tag-4p1l-dht","tag-4p1l-dht-preamp","tag-bartola-gyrator","tag-bartola-gyrator-pcb","tag-gyrator","tag-gyrator-pcb"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1rz","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5553","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=5553"}],"version-history":[{"count":4,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5553\/revisions"}],"predecessor-version":[{"id":5582,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/5553\/revisions\/5582"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=5553"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=5553"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=5553"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}