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Old 27th August 2014, 05:50 PM   #1
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Exclamation Universal Guitar Padal power supply

Today I built a Universal 9volt dc power supply. It works fine. But i got some humming. Please rectify my circuits
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Old 27th August 2014, 06:24 PM   #2
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There's nothing wrong with your circuit.

Have you used fairly heavy wire for all the 0V connections ?
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Old 27th August 2014, 06:26 PM   #3
rayma is offline rayma  United States
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Originally Posted by rohansinha2000 View Post
Today I built a Universal 9volt dc power supply. It works fine. But i got some humming. Please rectify my circuits
You should measure around 16 VDC at the rectifier side. If it's much lower than that, the 4700uF capacitor could be bad.
The 4700uF capacitor should also be close to the rectifier's output.

Maybe there's rectifier noise coupling between the rectifier/4700uF part of the circuit and the regulator part.
The regulator's ground pin and the other caps should be all connected together separately from the rectifier/4700uF parts,
and a pair of +/- wires run to the 4700uF, twisted together if possible, connecting close to the capacitor's body, not farther down its leads.
There are current pulses flowing through the leads of the 4700uF from the rectifier, and the farther from the capacitor's body that you connect
the leads from the regulator, the more noise you will couple into it.

Last edited by rayma; 27th August 2014 at 06:50 PM.
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Old 27th August 2014, 06:49 PM   #4
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Can you be sure the hum originates from the supply? I suspect it is in the guitar signal, as is usual with many guitars.

To reiterate, the "weakest link" for the introduction of hum into an electric guitar signal is the guitar itself. The supply however good, will never improve a noisy electric guitar signal.
Every new piece of knowledge pushes something else out of my brain - Homer.....................Simpson

Last edited by mondogenerator; 27th August 2014 at 06:51 PM.
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Old Yesterday, 07:36 AM   #5
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The problem with connecting multiple effect units to a single power supply is the additional audio/power ground connections that are created. Ground loops or a better way of explaining it might be parallel ground/return routing.

If this is the problem, you could try to build individual DC power supplies connected to single AC source. keeping all the ground connections separate.
Regards Mark.

Last edited by Mark Whitney; Yesterday at 07:44 AM.
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Old Yesterday, 05:43 PM   #6
zintolo is offline zintolo  Italy
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Seems a typical ground loop.
All modern power supplies for guitar/bass stomp boxes have separeted grounds for each (group of) outlet.

Sent from abroad. At least.
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