Blowing 5534's....

[ramshackles]

there is no squealing....got there a few posts ago.

 

[ricardo]

there is no squealing....got there a few posts ago.

Not even when you "touch the input transformer ... at full gain...." ?

 

[abbey road d enfer]

But there are a few things I see not done consistently which is maybe odd as there is surely one 'best' solution?

No. That's a common belief that "star ground" will cure everything including ingrown nails, but in fact one has to analyse the complete system. The receipes exposed by "Pin 1 gurus" work well only in the limits of an all-balanced single-input/single-output device. Once you have to deal with multiple unbalanced I/O's, one has to analyse the current flows. That includes ripple current from the PSU, currents due to differing power grounds (earth), currents into the various stages. Hierarchical ground arrangement is system-dependant, so a single universal answer does not exist.

What I often hear quoted is that other grounds should also meet up with the safety earth & chassis at the same point (the star point) and only at that point...

That is not a necessity. In particular joining the PSU reference to the input ground is generally a receipe for disaster.

But what often seems to happen is that the power common is passed on to the audio widget PCB and connected to it's signal reference?

That is a sound decision based on the analysis of current flow.

Is it better to keep power common separate and have it and the signal reference meet up at the star point, like so?:

Depends which point of the PSU is used as reference. The point where the smoothing caps meet is different than the point where the regulator's reference meet. Think of PCB tracks as resistors.

But the power common would still need to be passed on to the audio PCB (which I think is what ricardo is getting at) so power related components on the audio PCB can be grounded to the power common, not the signal reference?

That is hierarchical ground, where the load's reference is connected as hard as can be to the power source's reference, and to the stage's reference.

So the power common would be passed on to the audio PCB for this purpose, like so:

That would be a combination of hierarchical and star ground. Too much of a good thing. You have to make a choice. Use Ohm and Kirchoff. Avoid loops.

 

[V9977]

No. That's a common belief that "star ground" will cure everything including ingrown nails, but in fact one has to analyse the complete system. The receipes exposed by "Pin 1 gurus" work well only in the limits of an all-balanced single-input/single-output device. Once you have to deal with multiple unbalanced I/O's, one has to analyse the current flows. That includes ripple current from the PSU, currents due to differing power grounds (earth), currents into the various stages. Hierarchical ground arrangement is system-dependant, so a single universal answer does not exist.

Well said!