{"id":316,"date":"2012-06-23T09:05:01","date_gmt":"2012-06-23T09:05:01","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=316"},"modified":"2012-06-23T09:05:01","modified_gmt":"2012-06-23T09:05:01","slug":"26-thd-analysis","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2012\/06\/23\/26-thd-analysis\/","title":{"rendered":"26 THD analysis"},"content":{"rendered":"<figure id=\"attachment_317\" aria-describedby=\"caption-attachment-317\" style=\"width: 800px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-tubes.jpg\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" data-attachment-id=\"317\" data-permalink=\"https:\/\/www.bartola.co.uk\/valves\/2012\/06\/23\/26-thd-analysis\/26-tubes\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-tubes.jpg?fit=800%2C600&amp;ssl=1\" data-orig-size=\"800,600\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;}\" data-image-title=\"26-tubes\" data-image-description=\"\" data-image-caption=\"&lt;p&gt;26 tubes&lt;\/p&gt;\n\" data-large-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-tubes.jpg?fit=800%2C600&amp;ssl=1\" class=\"size-full wp-image-317\" title=\"\" src=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-tubes.jpg?resize=800%2C600\" alt=\"\" width=\"800\" height=\"600\" srcset=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-tubes.jpg?w=800&amp;ssl=1 800w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-tubes.jpg?resize=300%2C225&amp;ssl=1 300w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-tubes.jpg?resize=400%2C300&amp;ssl=1 400w\" sizes=\"auto, (max-width: 709px) 85vw, (max-width: 909px) 67vw, (max-width: 984px) 61vw, (max-width: 1362px) 45vw, 600px\" \/><\/a><figcaption id=\"caption-attachment-317\" class=\"wp-caption-text\">ux226 globe valves<\/figcaption><\/figure>\n<p>As I&#8217;m proud of my 26 DHT pre-amp and also looking to use this valve as the first stage of my 4-65a SE amplifier shortly, I looked at how linear this valve is.<\/p>\n<p>Unfortunately I don&#8217;t have an extensive set of valves of same brands, so albeit I have about 40 valves if this type there is a big mix of different brands and many of them are used ones. Having said that, I think this may be the case of many of you out there, so I think that probably the results of this test may be relevant to you (if you are still reading this post).<\/p>\n<p>So in summary, this is the sample set I tested:<\/p>\n<ul>\n<li>39 valves<\/li>\n<li>12 brands<\/li>\n<li>ST (34 valves) and Globe (5 valves)<\/li>\n<li>Type: 26, 226 and 326<\/li>\n<li>State: used (80%) and NOS (20%)<\/li>\n<\/ul>\n<p>All DUT were tested with the same test set and operating point:<\/p>\n<ul>\n<li>\u00a0Operating point: Ia=5.5mA and Vg=-10V<\/li>\n<li>Anode load: Cascoded DN2540 CCS set to Ia<\/li>\n<li>Test signal: 1kHz, Adjusted to obtain Vo=10Vrms (+22.22dBu)<\/li>\n<li>THD analysis: Audiotester via Pete Millett&#8217;s interface:\n<ul>\n<li>\u00a032768 sample FFT (2.96Hz resolution)<\/li>\n<li>256 averaged windows<\/li>\n<li>Van Hann window<\/li>\n<li>THD for H2+H3+H4<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>So in summary the results showed that you should expect a 26 to have around 0.08% (Std \u00a0Dev = 0.00047). Here is an histogram showing a summary of the tests done:<\/p>\n<figure id=\"attachment_318\" aria-describedby=\"caption-attachment-318\" style=\"width: 762px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-histogram.png\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" data-attachment-id=\"318\" data-permalink=\"https:\/\/www.bartola.co.uk\/valves\/2012\/06\/23\/26-thd-analysis\/26-thd-histogram\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-histogram.png?fit=762%2C591&amp;ssl=1\" data-orig-size=\"762,591\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;}\" data-image-title=\"26 thd histogram\" data-image-description=\"\" data-image-caption=\"&lt;p&gt;26 THD histogram&lt;\/p&gt;\n\" data-large-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-histogram.png?fit=762%2C591&amp;ssl=1\" class=\"size-full wp-image-318\" title=\"26 thd histogram\" src=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-histogram.png?resize=762%2C591\" alt=\"\" width=\"762\" height=\"591\" srcset=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-histogram.png?w=762&amp;ssl=1 762w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-histogram.png?resize=300%2C232&amp;ssl=1 300w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-histogram.png?resize=386%2C300&amp;ssl=1 386w\" sizes=\"auto, (max-width: 709px) 85vw, (max-width: 909px) 67vw, (max-width: 984px) 61vw, (max-width: 1362px) 45vw, 600px\" \/><\/a><figcaption id=\"caption-attachment-318\" class=\"wp-caption-text\">26 THD histogram<\/figcaption><\/figure>\n<p>Looking at brands, the following average THD ranking was produced:<\/p>\n<figure id=\"attachment_320\" aria-describedby=\"caption-attachment-320\" style=\"width: 734px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-by-brand.png\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" data-attachment-id=\"320\" data-permalink=\"https:\/\/www.bartola.co.uk\/valves\/2012\/06\/23\/26-thd-analysis\/26-thd-by-brand\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-by-brand.png?fit=734%2C296&amp;ssl=1\" data-orig-size=\"734,296\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;}\" data-image-title=\"26 thd by brand\" data-image-description=\"\" data-image-caption=\"&lt;p&gt;26 THD by Manufacturer\/Brand&lt;\/p&gt;\n\" data-large-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-by-brand.png?fit=734%2C296&amp;ssl=1\" class=\"size-full wp-image-320\" title=\"26 thd by brand\" src=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-by-brand.png?resize=734%2C296\" alt=\"\" width=\"734\" height=\"296\" srcset=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-by-brand.png?w=734&amp;ssl=1 734w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-by-brand.png?resize=300%2C120&amp;ssl=1 300w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-thd-by-brand.png?resize=500%2C201&amp;ssl=1 500w\" sizes=\"auto, (max-width: 709px) 85vw, (max-width: 909px) 67vw, (max-width: 984px) 61vw, (max-width: 1362px) 45vw, 600px\" \/><\/a><figcaption id=\"caption-attachment-320\" class=\"wp-caption-text\">26 THD by Manufacturer\/Brand<\/figcaption><\/figure>\n<p>Interesting to find National Union leading the chart. I found RCA and Sylvania to be my preferred ones in terms of sound. THD shown above are average of sample sets of 4 valves or more. Although I tested 12 brands in total, some of them were just a pair so they are not a representative subset.<\/p>\n<p>Finally, here is a sample THD of a very nice 26 valve:<\/p>\n<figure id=\"attachment_321\" aria-describedby=\"caption-attachment-321\" style=\"width: 584px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-THD-best.jpg\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" data-attachment-id=\"321\" data-permalink=\"https:\/\/www.bartola.co.uk\/valves\/2012\/06\/23\/26-thd-analysis\/26-thd-best\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-THD-best.jpg?fit=1243%2C772&amp;ssl=1\" data-orig-size=\"1243,772\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;}\" data-image-title=\"26 THD best\" data-image-description=\"\" data-image-caption=\"&lt;p&gt;26 DUT&lt;\/p&gt;\n\" data-large-file=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-THD-best.jpg?fit=840%2C521&amp;ssl=1\" class=\"size-large wp-image-321\" title=\"26 THD best\" src=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-THD-best-1024x635.jpg?resize=584%2C362\" alt=\"\" width=\"584\" height=\"362\" srcset=\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-THD-best.jpg?resize=1024%2C635&amp;ssl=1 1024w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-THD-best.jpg?resize=300%2C186&amp;ssl=1 300w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-THD-best.jpg?resize=483%2C300&amp;ssl=1 483w, https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2012\/06\/26-THD-best.jpg?w=1243&amp;ssl=1 1243w\" sizes=\"auto, (max-width: 584px) 85vw, 584px\" \/><\/a><figcaption id=\"caption-attachment-321\" class=\"wp-caption-text\">26 DUT<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<p>I wish I could have a bigger collection of 26 to improve the accuracy of this statistical analysis. Either way you can get a view of what you should expect from this great valve&#8230;<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>As I&#8217;m proud of my 26 DHT pre-amp and also looking to use this valve as the first stage of my 4-65a SE amplifier shortly, I looked at how linear this valve is. Unfortunately I don&#8217;t have an extensive set of valves of same brands, so albeit I have about 40 valves if this type &hellip; <a href=\"https:\/\/www.bartola.co.uk\/valves\/2012\/06\/23\/26-thd-analysis\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;26 THD analysis&#8221;<\/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":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[12,67,1,38],"tags":[779,103,780,101,57,72,102,100,784],"class_list":["post-316","post","type-post","status-publish","format-standard","hentry","category-dht-valves","category-thd","category-uncategorized","category-valve-tester","tag-779","tag-26-thd-analysis","tag-4-65a","tag-audiotester","tag-ccs","tag-dn2540","tag-fft","tag-pete-millett","tag-thd"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-56","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/316","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=316"}],"version-history":[{"count":2,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/316\/revisions"}],"predecessor-version":[{"id":322,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/316\/revisions\/322"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=316"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=316"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=316"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}