{"id":3932,"date":"2014-11-08T17:49:43","date_gmt":"2014-11-08T17:49:43","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=3932"},"modified":"2014-11-09T19:56:58","modified_gmt":"2014-11-09T19:56:58","slug":"01a-preamp-gen2-build-part-1","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2014\/11\/08\/01a-preamp-gen2-build-part-1\/","title":{"rendered":"01a Preamp Gen2: Build (Part 1)"},"content":{"rendered":"

The first step in the building process of this preamp<\/a> has been to get the active load boards ready. A reasonably quick assembly process this afternoon:<\/p>\n

\"IMG_0335\"<\/a>I’m aiming for a compact build here, so I mounted both boards with stand-off made of brass. The trimpots are at the top so I can adjust the operating point of the 01a.<\/p>\n

After several careless tests, I blew some 2SK170 as I exceeded the VGS levels and also some DN2540 went pear-shaped with them so decided to add a protection 18V zener which I had at hand:<\/p>\n

\"01a<\/a>Also changed some of the component values based on what I have in my box currently. Nothing major but the frequency response is yet to be checked. I did a quick frequency sweep and the HF response was flat up to 60kHz or more. More than needed.<\/p>\n

I added the cascoded LND150 to help improving the temperature response. Will see how this works in practice.<\/p>\n

Now, looking at the FR response we can see that at very low signal level (e.g. 100mV) the output of this stage has H2 level at -75dB and the following harmonics at least 10dB down.<\/p>\n

\"01a<\/a><\/p>\n

When looking at the response with a 1V drive (which is a very high input level for this stage in my system), the distortion increases from 0.02% to nearly 0.05% with the other harmonics 20dB below. H5 is higher than H3 surprisingly and even 2dB higher than H4:<\/p>\n

\"01a<\/a><\/p>\n

So far, response has been as predicted and it mostly depends on the type of 01a valve used. I used a globe CX201a I have on the bench ready for abuse, not my best valve at this point for testing!<\/p>\n

Will continue…<\/p>\n

 <\/p>\n

 <\/p>\n

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

The first step in the building process of this preamp has been to get the active load boards ready. A reasonably quick assembly process this afternoon:<\/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":[12,156,67,5],"tags":[10,309,650,59,6,186],"class_list":["post-3932","post","type-post","status-publish","format-standard","hentry","category-dht-valves","category-pre-amplifier-valves","category-thd","category-valves","tag-01a","tag-01a-preamp","tag-01a-tube","tag-cx301a","tag-dht","tag-dht-preamp"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-11q","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/3932","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=3932"}],"version-history":[{"count":3,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/3932\/revisions"}],"predecessor-version":[{"id":3942,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/3932\/revisions\/3942"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=3932"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=3932"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=3932"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}