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Audio and Video Talk
Valves / Vacuum Tubes
Philips AG9015 - interesting output stage
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<blockquote data-quote="Steerpike" data-source="post: 1044126" data-attributes="member: 807"><p>This is what Philips called their Series Balanced Output.</p><p>The AG9014, and the radiogram I have (model lost to memory) have no output transformers and require the 800R loudspeakers.</p><p>It has an astonishing power bandwidth for a 'home' hi fi of the 1950s of 7Hz to 50kHz. (THD 0.2%)</p><p>The AG9015 and 9018 had transformers so they could be used with 8R loudspeakers too, with lesser output power (12W).</p><p></p><p>The transformer offers the added advantage of screen grid modulation (a kind of "ultra linear" operation), which is impossible in the capacitor-only output stage.</p><p></p><p>The EL86 was created specifically for this topology - high anode current at moderate anode voltage, but particularly, the heater insulation is very good, since the "top" valve's cathode can rise to several hundred volts above the heater supply - which something like an EL84 will not survive. Sometimes an EL84 was used as the "bottom" valve.</p><p>You can get quite a shock from the speaker terminals (for safety they are somewhat like deeply recessed 3-pin XLR sockets)</p></blockquote><p></p>
[QUOTE="Steerpike, post: 1044126, member: 807"] This is what Philips called their Series Balanced Output. The AG9014, and the radiogram I have (model lost to memory) have no output transformers and require the 800R loudspeakers. It has an astonishing power bandwidth for a 'home' hi fi of the 1950s of 7Hz to 50kHz. (THD 0.2%) The AG9015 and 9018 had transformers so they could be used with 8R loudspeakers too, with lesser output power (12W). The transformer offers the added advantage of screen grid modulation (a kind of "ultra linear" operation), which is impossible in the capacitor-only output stage. The EL86 was created specifically for this topology - high anode current at moderate anode voltage, but particularly, the heater insulation is very good, since the "top" valve's cathode can rise to several hundred volts above the heater supply - which something like an EL84 will not survive. Sometimes an EL84 was used as the "bottom" valve. You can get quite a shock from the speaker terminals (for safety they are somewhat like deeply recessed 3-pin XLR sockets) [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
Philips AG9015 - interesting output stage
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