Rectifier Noise
If you're getting rectifier noise in the audio your ground layout is bad. I design amps over 1000W with 100db and better signal to noise ratios and never get rectifier noise in the audio. None. Nothing but the hiss from the electrons bumping into each other.\
You have to make sure that the loop of rectifiers/capacitors is a separate loop from capacitors/audio. If the ground between the amp and the filter caps shares any conductor with the rectifiers, you will get rectifier noise.
In a bi-polar power supply, the transformer center tap must go directly to the common point between the two filter caps. And this common point must be very, very heavy. Then the ground from the amplifier connects there. This makes it so you have separate paths for the current that charges the capacitors and the path that supplies power to the amplifier.
Any deviation from this will degrade the s/n ratio.
If you're getting rectifier noise in the audio your ground layout is bad. I design amps over 1000W with 100db and better signal to noise ratios and never get rectifier noise in the audio. None. Nothing but the hiss from the electrons bumping into each other.\
You have to make sure that the loop of rectifiers/capacitors is a separate loop from capacitors/audio. If the ground between the amp and the filter caps shares any conductor with the rectifiers, you will get rectifier noise.
In a bi-polar power supply, the transformer center tap must go directly to the common point between the two filter caps. And this common point must be very, very heavy. Then the ground from the amplifier connects there. This makes it so you have separate paths for the current that charges the capacitors and the path that supplies power to the amplifier.
Any deviation from this will degrade the s/n ratio.
Dan Fraser,
Can this be solved by using two separate bridges and separate transformer windings? (in the bi-polar case)
Menno
Can this be solved by using two separate bridges and separate transformer windings? (in the bi-polar case)
Menno
Wiring
No, the configuration must be correct. The current path from the rectifiers to the filters cannot share any conductors with the current path from the filters to the audio circuitry. The only place where this cannot be avoided is between the ground pins of the two capacitors assuming you are doing a balanced power supply. In this case, the conductor between the ground leads has to be very heavy. Like 8 gauge wire or a PCB trace at least 12mm wide.
To this conductor the center tap connects. The audio ground will connect between these two filters as well.
This point is also where the "ground" lead of your speakers must connect. Not at the amplifier.
I sometimes also put .01 uFd caps across each diode in thebridge to soften the spikes though in reality, if the grounding is done right you won't need them.
Also, the wires from the bridge must go directly to the capacitors. Then the power wires to the audio circuit comes from the capacitor. This forces all the rectifier current through the capacitors. DO NOT connect the bridge output to your circuit then run wires to the cap. Because that would end up with audio power sharing a conductor with rectifier current.
The simple rule is that the rectifier/filter current loop cannopt share any conductors with the filter/load current loop. Similarly, the speaker ground current must NOT share any conductors with the lower level audio signals. If they do, you will get spurious oscillation and coloration of the sound.
No, the configuration must be correct. The current path from the rectifiers to the filters cannot share any conductors with the current path from the filters to the audio circuitry. The only place where this cannot be avoided is between the ground pins of the two capacitors assuming you are doing a balanced power supply. In this case, the conductor between the ground leads has to be very heavy. Like 8 gauge wire or a PCB trace at least 12mm wide.
To this conductor the center tap connects. The audio ground will connect between these two filters as well.
This point is also where the "ground" lead of your speakers must connect. Not at the amplifier.
I sometimes also put .01 uFd caps across each diode in thebridge to soften the spikes though in reality, if the grounding is done right you won't need them.
Also, the wires from the bridge must go directly to the capacitors. Then the power wires to the audio circuit comes from the capacitor. This forces all the rectifier current through the capacitors. DO NOT connect the bridge output to your circuit then run wires to the cap. Because that would end up with audio power sharing a conductor with rectifier current.
The simple rule is that the rectifier/filter current loop cannopt share any conductors with the filter/load current loop. Similarly, the speaker ground current must NOT share any conductors with the lower level audio signals. If they do, you will get spurious oscillation and coloration of the sound.
Caps across the DC side of the rectifier are common as mud (and I agree with using a few in parallel, for better temperature dispersion, among other things), but are the original posts talking about putting caps over the AC side of the rectifier? I always thought caps on the DC side were just for voltage smoothing, that's all. Maybe noise is another word for it...
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