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In the Forum: Melquiades Amplifier
In the Thread: A different breed of 6C33C amplifier.
Post Subject: 60Hz humPosted by KOTriode on: 11/2/2011
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It's 60Hz hum, caused by both mechanical and magnetic field coupling to the output transformer. I used a toroidal transformer and thought it would not caused this problem but it did. When using an external power supply for both B+ and heater (AC), the noise went down to around -74db, another 12db improvement. The output transformer is 1:1 and does not have magnetic shield, it picked hum easily. So, for now I just use the preamp the way it is, but in the future, if I build another 6C33C preamp, which I certainly will, I will have the power supply on separate chassis.
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