{"id":7303,"date":"2018-03-25T20:46:02","date_gmt":"2018-03-25T19:46:02","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=7303"},"modified":"2018-03-25T20:51:02","modified_gmt":"2018-03-25T19:51:02","slug":"eml-20a-dht-preamp","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2018\/03\/25\/eml-20a-dht-preamp\/","title":{"rendered":"EML-20A DHT Preamp"},"content":{"rendered":"

Recently I posted<\/a> about this<\/a> amazing DHT. Although my original intent was to use them as part of my Parafeed headphone project, I decided to try them as first stage on my system. I have been playing lately with mid-mu DHTs with great success, and this valve didn’t let me down at all.<\/p>\n

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

<\/p>\n

The EML-20A likes an operating point above 200V to get its best. If you want to use it as a driver, you should aim at 220V\/16mA operating point. You can maximise output at minimum distortion, like I showed on my last post about this valve.<\/p>\n

The Mule update<\/h2>\n

Best way to test this valve was to pick up my Mule<\/a> breadboard and get the preamp up and running in a few hours. The hacking is pretty simple:<\/p>\n

    \n
  1. The filament regulators are set to 1.4A and aiming a filament voltage equal of below 5V.<\/li>\n
  2. \u00a0The filament resistor is changed to 2.5\u03a9. In my case I paralleled 4 10\u03a9\/20W Russian NOS wire-wound resistors.<\/li>\n
  3. The gyrator is set to 205V anode and current is measured to be around 10mA. This is due to my limited HT. If you can, you can push it up more to 220-230V to achieve 15-16mA of anode current. You will need an HT of 280-300V to provide enough signal headroom as well as allow the MOSFETs to operate properly<\/li>\n<\/ol>\n

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

    Impressions<\/h2>\n

    I was very impressed when I tested these. The linearity as well as the true-mesh anode makes this valve a fantastic device. The level of detail and sound of this valve is amazing, I put it just at the top of my list with the 01a and the VT25\/801A ones. Despite not having thoriated tungsten filaments, it sounds superb. The dynamics and gain seems to match well with my 4P1L PSE output stage. Not microphonic at all! I was slightly concerned about potential hum pick up, but on my system is dead quiet.<\/p>\n

    I will keep these running for a while. I just returned the Elrog ER801a prototypes back to Thomas Mayer, so have good time to listen to these valves in detail.<\/p>\n","protected":false},"excerpt":{"rendered":"

    Recently I posted about this amazing DHT. Although my original intent was to use them as part of my Parafeed headphone project, I decided to try them as first stage on my system. I have been playing lately with mid-mu DHTs with great success, and this valve didn’t let me down at all.<\/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_feature_clip_id":0,"_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":[10,1136,903,6,1135,1138,1125,1092,1137,1134,875,1139,118],"class_list":["post-7303","post","type-post","status-publish","format-standard","hentry","category-valves","tag-01a","tag-anode-mesh","tag-bartola-gyrator-pcb","tag-dht","tag-dht-mesh","tag-elr801a","tag-elrog","tag-emission-labs","tag-eml-20a","tag-eml20a","tag-gyrator-pcb","tag-mid-mu-dht","tag-vt-25"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2r2tK-1TN","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7303","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=7303"}],"version-history":[{"count":4,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7303\/revisions"}],"predecessor-version":[{"id":7311,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/posts\/7303\/revisions\/7311"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=7303"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/categories?post=7303"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/tags?post=7303"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}