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Valves / Vacuum Tubes
Radford STA 15 Technical Discussion
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<blockquote data-quote="charles" data-source="post: 1043087" data-attributes="member: 2759"><p>From handsome:</p><p></p><p>"[member=144]Ampdog[/member] interestingly the original STA12 Radfords did use a "proper" pentode connection with screen bypassed to the cathode...I haven't read all the articles on their design but perhaps the reasoning for that move is mentioned somewhere?""</p><p></p><p>This is not correct, there is sometimes some misconception regarding the Radford's model numbers. </p><p></p><p>The Radford STA12 is a derivative of the Mullard 5/20 amplifier. It uses: EF86, ECC83 and EL34 valves.</p><p></p><p>The STA15 MkII was the first Radford that utilised the Triode/Pentode configuration. The circuit diagram is basically the same as the MKIII. Its output transformers differs in size, it is physically smaller and used different plugs and sockets compared to the MKIII. It has its own pre-amplifier. </p><p></p><p>On the forum is a posting regarding the Radford STA12 restoration.</p><p></p><p>https://www.avforums.co.za/index.php?topic=51226.0</p></blockquote><p></p>
[QUOTE="charles, post: 1043087, member: 2759"] From handsome: "[member=144]Ampdog[/member] interestingly the original STA12 Radfords did use a "proper" pentode connection with screen bypassed to the cathode...I haven't read all the articles on their design but perhaps the reasoning for that move is mentioned somewhere?"" This is not correct, there is sometimes some misconception regarding the Radford's model numbers. The Radford STA12 is a derivative of the Mullard 5/20 amplifier. It uses: EF86, ECC83 and EL34 valves. The STA15 MkII was the first Radford that utilised the Triode/Pentode configuration. The circuit diagram is basically the same as the MKIII. Its output transformers differs in size, it is physically smaller and used different plugs and sockets compared to the MKIII. It has its own pre-amplifier. On the forum is a posting regarding the Radford STA12 restoration. https://www.avforums.co.za/index.php?topic=51226.0 [/QUOTE]
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Audio and Video Talk
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Radford STA 15 Technical Discussion
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