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Old 12th December 2012, 09:48 PM   #1
dLab is offline dLab  Sweden
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Default Building a beast: Stereo EL84 auto bias PP tube amp

Just started to build this stereo tube amplifier based on 4 x EL84 and 2 x 6N2P tubes from Die Röhre, Wulfert audio.
Wondering perticulary how to combine volume potentiometer with balanced and unbalanced input (any sugestions). And if power transformer is not shield, it should not affect the quality of sound? If anyone has experience building this kit, all tips will be much appreciated...
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Old 12th December 2012, 10:11 PM   #2
cotdt is offline cotdt  United States
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You can add a toggle switch that can accept either unbalanced or balanced input. The volume pot would be a 4-gang.

I've always had problems having the power transformer so close. It would hum faintly.
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Old 19th July 2014, 12:38 PM   #3
dLab is offline dLab  Sweden
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The amp is almost built to 100%. Some small things need to be adjusted. I used your idea with the toggle switch. I got terrible switching noise. Any suggestions to eliminate this?
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Old 19th July 2014, 07:38 PM   #4
DF96 is offline DF96  England
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Signal switches must have identical DC levels on both sides. This may require extra coupling caps and resistors, or get used to never switching when the amp is turned on.
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