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Audio and Video Talk
Valves / Vacuum Tubes
Restoration of a Leak Stereo 60 Valve amplifier
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<blockquote data-quote="Family_Dog" data-source="post: 1132059" data-attributes="member: 82"><p>It is used to ensure that the filaments them selves have a ground reference and not left floating. Valves have high impedances and none of the constituent elements inside the valve should have no earthing reference as this could cause instability and/or hum. The use of a centre-tapped filament transformer balances out any possible hum interference from the filament supplies.</p><p></p><p>Older amplifiers have a much lower sensitivity input level than modern amplifiers and thus are more susceptible to AC hum-pickup. Anything that can lower the risk of this induced stray AC hum pickup is a good idea.</p><p></p><p>You could eliminate the filament centre taps and earth one side of the 6v winding only but I have always used centre-taps, my valve amps have no hum. Another work-around if no centre taps is to use two 100-ohm resistors in series across the 6v winding and earth the centre connection.</p><p></p><p>Saying this, I have no idea what method was used in the Leak 60, all the above in my opinion.</p><p></p><p><strong>EDIT: </strong>I see I did save the Leak 60 schematic, Leak also used the 3.15 - 0 - 3.15 filament configuration, centre-tap earthed.</p><p></p><p></p><p>-F_D</p></blockquote><p></p>
[QUOTE="Family_Dog, post: 1132059, member: 82"] It is used to ensure that the filaments them selves have a ground reference and not left floating. Valves have high impedances and none of the constituent elements inside the valve should have no earthing reference as this could cause instability and/or hum. The use of a centre-tapped filament transformer balances out any possible hum interference from the filament supplies. Older amplifiers have a much lower sensitivity input level than modern amplifiers and thus are more susceptible to AC hum-pickup. Anything that can lower the risk of this induced stray AC hum pickup is a good idea. You could eliminate the filament centre taps and earth one side of the 6v winding only but I have always used centre-taps, my valve amps have no hum. Another work-around if no centre taps is to use two 100-ohm resistors in series across the 6v winding and earth the centre connection. Saying this, I have no idea what method was used in the Leak 60, all the above in my opinion. [B]EDIT: [/B]I see I did save the Leak 60 schematic, Leak also used the 3.15 - 0 - 3.15 filament configuration, centre-tap earthed. -F_D [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
Restoration of a Leak Stereo 60 Valve amplifier
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