Hi all,
I've been recently looking at grounding in the purpose to make a high end mixer with multiple balanced inputs and I won't lie, it is giving me some headaches.
I've read a lot, but couldn't find concrete answers about this. For a balanced line input, Rane Note : "Grounding and Shielding Audio Devices" suggests to chassis-grounding the pin 1 of XLR with the smallest path to chassis as shield is the carrier of interferences and the length of this wire determines the filter frequency in RF domain.
The best way to do so that I've found is to use Neutrik XLR connectors such as the NC3FAAH1 which incorporate a direct path from pin 1 to the chassis with a sharp piercing tab.
But in star grounding, we often talk about connecting ground of our system to one point of the chassis only, as it is difficult to predict return path currents and that can cause internal ground loops to happen.
So I'm kind of torn between having the shortest path to chassis and therefore having all Neutrik XLRs with individual connections to chassis, or connecting all pins 1 together with a thick wire and sending it to only one chassis point but with the risk of sending more RF interferences to others PCBs.
What do you guys think or would do?
Thanks for solid explanations or experience feedback.
Cheers,
I've been recently looking at grounding in the purpose to make a high end mixer with multiple balanced inputs and I won't lie, it is giving me some headaches.
I've read a lot, but couldn't find concrete answers about this. For a balanced line input, Rane Note : "Grounding and Shielding Audio Devices" suggests to chassis-grounding the pin 1 of XLR with the smallest path to chassis as shield is the carrier of interferences and the length of this wire determines the filter frequency in RF domain.
The best way to do so that I've found is to use Neutrik XLR connectors such as the NC3FAAH1 which incorporate a direct path from pin 1 to the chassis with a sharp piercing tab.
But in star grounding, we often talk about connecting ground of our system to one point of the chassis only, as it is difficult to predict return path currents and that can cause internal ground loops to happen.
So I'm kind of torn between having the shortest path to chassis and therefore having all Neutrik XLRs with individual connections to chassis, or connecting all pins 1 together with a thick wire and sending it to only one chassis point but with the risk of sending more RF interferences to others PCBs.
What do you guys think or would do?
Thanks for solid explanations or experience feedback.
Cheers,
There is ground and there is earthing.
Pin 1 of the XLRs should go to chassis ground, otherwise known as earth.
The ground is split into power supply ground, chassis ground (earth) and signal ground.
Signal ground meets power ground at one point only (start ground).
Earth is connected to all chassis parts and connects to the mains earth through your three pin mains lead.
Some use a double diode and 100 Ohm resistor to connect the star ground to earth. This helps to avoid hum loops but continues to afford safety through the diodes to ground. The 100 Ohm resistor acts to stop any voltage build up (along with the diodes).
Pin 1 of the XLRs should go to chassis ground, otherwise known as earth.
The ground is split into power supply ground, chassis ground (earth) and signal ground.
Signal ground meets power ground at one point only (start ground).
Earth is connected to all chassis parts and connects to the mains earth through your three pin mains lead.
Some use a double diode and 100 Ohm resistor to connect the star ground to earth. This helps to avoid hum loops but continues to afford safety through the diodes to ground. The 100 Ohm resistor acts to stop any voltage build up (along with the diodes).
I get what you mean, but I've seen in a lot of designs that chassis grounding is taken at only one point. My question was pointing out if multiple chassis grounding can be made through the earth wire as usual but also pin 1 XLRs without having to much trouble in the internal system (return flow currents that would disturb the others PCBs).
Pin 1 of the XLRs are screens and as such not connecred to the signal ground. Ye, pin 1 of the XLRs can be connected to the chassis in multiple points as no current passes to the signal side. This is assuming you use balanced line wiring.
my xlr socket have a ground latch: G on the diagram below.
They are screwed in the chassis, which makes contact with the G latch, then I solder a little wire from G to pin 1, which effectively connect the XLR socket AND pin 1 to the chassis ground.
Works perfectly, no hum.
https://static.bax-shop.es/image/product/666460/2292321/757d6aa6/450x450/1594118574NE97427_1.JPG
They are screwed in the chassis, which makes contact with the G latch, then I solder a little wire from G to pin 1, which effectively connect the XLR socket AND pin 1 to the chassis ground.
Works perfectly, no hum.
https://static.bax-shop.es/image/product/666460/2292321/757d6aa6/450x450/1594118574NE97427_1.JPG
In an XLR balanced interconnect system, Pin 1 is a shield (not a circuit ground) and should be attached to a metal chassis at it's connector.
The metal chassis is also a shield.
Other connections to a metal chassis:
a] Safety Ground/Protective Earth to the chassis near where the AC power enters the chassis.
b] audio circuit common at one point near the audio input connectors.
c] DC supply common at the same chassis point as the audio circuit common.
* * * * * * * * *
While there is continuity to Planet Earth, there is no connection to Planet Earth.
The metal chassis is also a shield.
Other connections to a metal chassis:
a] Safety Ground/Protective Earth to the chassis near where the AC power enters the chassis.
b] audio circuit common at one point near the audio input connectors.
c] DC supply common at the same chassis point as the audio circuit common.
* * * * * * * * *
While there is continuity to Planet Earth, there is no connection to Planet Earth.