Hi everyone!
I just finished another project which is made of:
DC-blocker + soft start
toroidal transformer
Bridge rectifier
preamp
source selector + remote control module
BT_DAC
some VU meters
speaker protection
and of course power amps
Below two photos from early build stage to relate to:
Everything works flawlessly while this setup is powered in series with a bulb. Minimal hiss. No buzz/hum. But when I connect it to the same wall socket without bulb in series, I start to hear buzz from speakers. Also, transformer starts buzzing. When I remove top cover it is slightly less hearable, but with a cover screwed on it's beyond being acceptable.
Does any one have any idea what can cause such a behaviour?
I am aware that above setup is not described in much detail, but having in mind that all works well with the bulb it might be something trivial. However, if more details are needed - please do let me know and I'll update you with more data.
Thanks!
I just finished another project which is made of:
DC-blocker + soft start
toroidal transformer
Bridge rectifier
preamp
source selector + remote control module
BT_DAC
some VU meters
speaker protection
and of course power amps
Below two photos from early build stage to relate to:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Everything works flawlessly while this setup is powered in series with a bulb. Minimal hiss. No buzz/hum. But when I connect it to the same wall socket without bulb in series, I start to hear buzz from speakers. Also, transformer starts buzzing. When I remove top cover it is slightly less hearable, but with a cover screwed on it's beyond being acceptable.
Does any one have any idea what can cause such a behaviour?
I am aware that above setup is not described in much detail, but having in mind that all works well with the bulb it might be something trivial. However, if more details are needed - please do let me know and I'll update you with more data.
Thanks!
The bulb could be lowering the AC line voltage getting to the amp, so less buzzing.
Or else it's a ground loop that is removed by hooking up the bulb tester (no safety ground)?.
Post a schematic of both the amp and the bulb tester.
Or else it's a ground loop that is removed by hooking up the bulb tester (no safety ground)?.
Post a schematic of both the amp and the bulb tester.
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The bulb is a temperature dependent resistance, but a resistance in it. If the buzz is mechanical and acoustical, possibly the transformer is very near to saturation flux density or directly saturated, radiating magnetic flux outside the core. Perhaps you can reduce the transformer's input voltage trying a small inductance or capacitance in series to the transformer's primary and simulating the lamp resistance with the same or close value of impedance (Non dissipative).
The flux radiated away from the core may being picked up by the sensitive wiring or parts introducing it in the audio circuit.
The flux radiated away from the core may being picked up by the sensitive wiring or parts introducing it in the audio circuit.