Hai . I built an amplifier. details are as follows. a 12-0-12 5a transformer, power supply board with dual polarity output. A TDA 2030 sterio board 30 30w using four ICs , sterio tone control board using two ne5532 and a usb module that reads pendrive- memory card and fm. Everything is working fine . But usb module is causing a slightly high pitched hum. It goes away when disconnecting power to the USB module. It works on 5v supply. I changed the 7805 voltage regulator , connected it to the 12v part of main amplifier power supply. ( power supply board has three different outputs. Unregulated 12v dual for 2030 board( multimeter reads 14v dual since its not regulated), 15v regulated dual supply for ne5532( reads 14vdual even though 7815&7915 since 12v dual transformer) , and another 12v which then connects to regulator for USB module. I connected secondary of transfor to inputs of the inputs of these power supplies. The hum is just like some guitar amps that we can hear when no music playing at highest volume. I'm planning to add a powered subwoofer to output of 5532 preamp board. I think it causes loud hum in subwoofer since its low frequency. ( can hear hum only when the volume is high and USB POWER is connected. I didn't used a star ground on chassis. I don't ml know how to make a star ground. Please help.
No . Amplifier is of tda2030 in bridge. Speaker wires ( ve and -ve) comes straight to the output of 2030. One wire to one 2030 and the other wire to another 2030. Output from usb module comes to the input of tone control. Then its output goes to amplifier board. Usb module has remote . When I decrease volume using remote and increase it in tone control, hum increases. And when I increase volume in remote and decrease it in tone control, hum decreases.
Sounds like the USB module is producing the hum. In which case it could be picking it up from any source. Is the USB cable shielded? Is the module shielded? You can try isolating the USB power wires and putting a filtering capacitor in parallel.
Maybe the ground connection from the USB module to the tone control is bad.
Oh, another thing. Is the computer properly grounded? Multiple floating grounds produced by switching supplies can be a hum nightmare.
Usb module hum
Posted - Aug 12 2016 : 01:41:14 AM
