[sdiy] Eurorack Grounding Question

[Mike Bryant]

> My opinion about mindless automatic groundfill put everywhere is similar to what many others think about 100% blind recapping. With ground fill you have no control over return currents or ground currents whatever you call them. Sometimes I see ground fill made on PCBs in such pointless ways that captain Picard is facepalming in front of me even without closing my eyes.

I think part of the problem is the cheaper/free EDA tools happily through ground plane everywhere and inexperienced users assume doing that is all that is needed.  But in fact often what they have created is a mesh antennae for EMI rather than a sink.   I'm not saying ground planes aren't needed, quite the contrary as passing FCC part 15 without one is almost impossible with fast MCUs, but users need to understand how they work as much as they (hopefully) do the components connected to the PCB.


-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Roman Sowa
Sent: 31 December 2020 10:01
To: Steven Cook; Synth-diy at synth-diy.org
Subject: Re: [sdiy] Eurorack Grounding Question

My opinion about mindless automatic groundfill put everywhere is similar to what many others think about 100% blind recapping. With ground fill you have no control over return currents or ground currents whatever you call them. Sometimes I see ground fill made on PCBs in such pointless ways that captain Picard is facepalming in front of me even without closing my eyes.

In short, make separate groundfills for areas where you woudn't like to mix the signal, like mic preamp and stage light driver nearby. And link them only at the ground star point (which is not always possible, as in eurorack the ground star point is far away outside the module). But if you really need to have one, connect it to the "shield" ground that was talked over already in this subject. Obviously such groundfill should not link to any of the "real" signal ground traces anywhere

Ad.2 - DAC is analog component and should be treated as opamps and other sensitive audio circuit.

Roman

W dniu 2020-12-31 o 09:01, Steven Cook via Synth-diy pisze:
> Thank you for these answers. I think I'll go with Tony's recommendation. 
> The reason I have input jacks connected to the digital ground is 
> simply that they are connected to the microcontroller (via transistors 
> and reverse voltage protection diodes), so I assumed that the jacks 
> should be also - I'll change that.
> 
> I have a couple of follow-up questions:
> 
> 1. If I have a ground fill on the PCBs, which ground should it be 
> connected to?
> 
> 2. Which ground should the DAC be connected to?
> 
> ------ Original Message ------
> From: "Steven Cook via Synth-diy" <synth-diy at synth-diy.org>
> To: Synth-diy at synth-diy.org
> Sent: 29/12/2020 09:30:46
> Subject: [sdiy] Eurorack Grounding Question
> 
>> Hi, I'm designing a Eurorack module which uses a microcontroller. The 
>> PCB has separate analogue and digital grounds joined at the power 
>> input header, but I've realised since designing it that both grounds 
>> will also be shorted together by the front panel as there are input 
>> jacks connected to the digital ground and output jacks connected to 
>> the analogue ground. I assume this would create an ground loop. Would 
>> I be better off not bothering with separate grounds?
>>
>> Regards,
>>
>> Steven Cook
>>
>>
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