My schematic is below. The filaments are running directly off the 12VDC input. The only change to the schematic is i'm using a LT1054 instead of the MAX1044.
Linear vs Switch Mode Power Supply & Hum
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Dr Tony Balls
- Diode Debunker
I've built a tube driver in the BK Butler / Baja / Madbean Archibald vein and just noticed something that i've not come across before. I'm getting hum (120Hz) when using linear power supplies such as a Boss PSA-120T, but i'm not getting any hum when using a switch-mode power supply such as the Boss PSA-120S. I've tried it with a variety of power supplies and all of the linear ones hum, and all of the switch-mode ones are fine. Anyone know what's up with this?
My schematic is below. The filaments are running directly off the 12VDC input. The only change to the schematic is i'm using a LT1054 instead of the MAX1044.
My schematic is below. The filaments are running directly off the 12VDC input. The only change to the schematic is i'm using a LT1054 instead of the MAX1044.
-
mauman
- Resistor Ronker
The switch mode power supplies are filtering the 120Hz power line harmonic better than the linear supplies. I don't see any line noise filtering in the power section, and the LT1054 won't filter it out. Try adding an RC filter to the incoming +12V before the inverter: a series Schottky or small value resistor, and an EL cap of at least 100uF to ground. The cap will also serve as a reservoir for the inverter and op amps.