{"id":681,"date":"2012-10-07T08:14:40","date_gmt":"2012-10-07T08:14:40","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?page_id=681"},"modified":"2017-07-08T07:51:28","modified_gmt":"2017-07-08T06:51:28","slug":"71a-dht-pre-amplifier","status":"publish","type":"page","link":"https:\/\/www.bartola.co.uk\/valves\/dht-pre-amplifier\/71a-dht-pre-amplifier\/","title":{"rendered":"71a DHT pre-amplifier"},"content":{"rendered":"

This was my 71a DHT preamp incarnation. I reused existing circuitry so it can be improved. Firstly the top BSP129 should be an DN2540 with heatsink. P1 can be replaced with a LND150 depletion MOSFET CCS \u00a0and a resistor divider to improve the frequency response. R5 should be your preferred 100K stepped attenuator instead.<\/p>\n

I enjoyed this very much and will definitely encourage everyone to build it. I recall that the bass response wasn’t as good as the 4P1L despite anode resistance being low as well.<\/p>\n

Slight filament starvation to reduce microphony and DC regulation is provided by Rod Coleman boards<\/a>.<\/p>\n

Globe 71 are difficult to get hold of, but worth trying them.<\/p>\n

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

Here<\/a> are my earlier impressions and description of the circuit.<\/p>\n

Cheers,<\/p>\n

Ale<\/p>\n

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

This was my 71a DHT preamp incarnation. I reused existing circuitry so it can be improved. Firstly the top BSP129 should be an DN2540 with heatsink. P1 can be replaced with a LND150 depletion MOSFET CCS \u00a0and a resistor divider to improve the frequency response. R5 should be your preferred 100K stepped attenuator instead. I … Continue reading “71a DHT pre-amplifier”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":679,"menu_order":0,"comment_status":"open","ping_status":"open","template":"","meta":{"footnotes":""},"class_list":["post-681","page","type-page","status-publish","hentry"],"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/P2r2tK-aZ","jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/pages\/681","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/types\/page"}],"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=681"}],"version-history":[{"count":2,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/pages\/681\/revisions"}],"predecessor-version":[{"id":6555,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/pages\/681\/revisions\/6555"}],"up":[{"embeddable":true,"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/pages\/679"}],"wp:attachment":[{"href":"https:\/\/www.bartola.co.uk\/valves\/wp-json\/wp\/v2\/media?parent=681"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}