Dual Secondary or single center tapped psu?Ground advantage?

Thinking of using dual secondary as it has better grounding advantage as its not connected directly to the transformer center tap. I believe it might even have some noise advantage aswell.

What are the pros and cons of using dual secondaries with two bridges. Im about to build the pcb so any quick replies would be a great help.
 

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Mark Johnson

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2011-05-27 3:27 pm
Silicon Valley
If you've got Bob Cordell's power amp book, Section 16.1 "Alternative Supply Arrangements" (p.343) discusses weaknesses of the center tapped arrangement. However, Bob Cordell feels that the cost of a second diode bridge is a burdensome expense.

I personally feel that an extra £2.09 for a second 50 ampere bridge (link), is cheap insurance against transformer buzzing and the other ills mentioned in the book. I'd rather pay a piddling amount of money now, in exchange for years of greater listening enjoyment later. But I'm only building this for myself; it is assuredly not a commercial product that must compete in a vigorous and cutthroat marketplace, based on price.
 
R.Cordell did reach a conclusion.
On a fixed budget, I would opt for better rectifiers in the conventional arrangement
By conventional, he means Centre Tapped with one Bridge Rectifier.

That's the way I usually build my PSU. But I have done it with dual secondary and dual rectifiers, series connected at the outputs. with the equipment I have I cannot measure any difference in performance, except the lower voltage and the higher heat load that comes with the dual rectifiers.

I suspect that more sensitive measuring equipment and techniques may be able to discern an operational performance difference. I suspect that would show as reduced harmonics of the mains frequency infiltrating the audio circuits for the dual rectifier.

But I ask myself the question, if the audio artefacts of the centre tapped are @ <0.05mVac of Hum + Noise at the output of the amplifier, will reduced harmonics give any audible improvement in performance?

I have seen many FFT of amplifiers posted on this Forum. I cannot recall a test report that specifically looked for, or at, the difference in performance of the dual vs the single rectifier.

Maybe we could persuade those that have the knowledge and the equipment to do some comparison tests for us and settle the argument.
 
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For high power app's the B solution has the advantage of half the heat dissipated in the diodes.(and you gain 1 less diode voltage loss)
Mona
Yes. Nearly.

The power dissipated and the heat produced by the dual rectifier is double the single rectifier.
Each diode sees exactly the same current in both arrangements. That results in exactly the same heat in each diode and with double the number of diodes, one ends up with a build that has a doubled heat load to be lost via ventilation.
 
The only benefit of the dual bridge configuration is better ripple rejection if - and only if - the two secondary windings are not exactly the same. It remains simply a small difference between rectified voltages, which is usally without inconvenience.

Except for that, the double bridge configuration has only drawbacks (costs, size, heat...)
 
I am not sure that Fred has analysed the differences correctly. He has missed out some resistances/impedances.

But he is onto to something that is not easily measured with unsophisticated equipment. That is why I stated
I suspect that would show as reduced harmonics of the mains frequency infiltrating the audio circuits for the dual rectifier.

But I ask myself the question, if the audio artefacts of the centre tapped are @ <0.05mVac of Hum + Noise at the output of the amplifier, will reduced harmonics give any audible improvement in performance?