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Balanced grounding question regarding XLR Pin 1

post #1 of 14
7/26/09 at 4:46am
Thread Starter 
I remember grounding pin 1 inputs to the chassis of my balanced only Beta22.

I am in the process of building a Sabre32 DAC for my Beta22. My question is do I do the same for the Sabre32, does pin 1 connect to the chassis only? Therefore the Sabre outputs will only run to pins 2 and 3.

This article explains it as the best connection, but I still unsure...
Grounding and Shielding Audio Devices
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post #2 of 14
7/26/09 at 5:12am
Would not connecting pin1 to chassis on both ends cause a problem because the power supplies for the buf are in the same case as the dac?

I actually had a similar question.

Edit: I just read that link and now I think what I typed is possibly silly~
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post #3 of 14
7/26/09 at 5:53am
Pin 1 should be carrying SIGNAL ground and needs to be maintained. You should connect it on your Beta22 and Buffalo32 to SIGNAL GROUND. This should not be directly connected to Earth Ground without a ground loop breaker.
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post #4 of 14
7/26/09 at 6:19am
Aha! Yah that is what i was getting at.
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post #5 of 14
7/26/09 at 6:27am
Thread Starter 
Quote:
Originally Posted by FallenAngel View Post
Pin 1 should be carrying SIGNAL ground and needs to be maintained. You should connect it on your Beta22 and Buffalo32 to SIGNAL GROUND. This should not be directly connected to Earth Ground without a ground loop breaker.
Actually I was getting confused, I have input pin 1 of the Beta22 connected to ground signal and chassis as per amb recommendation for a balanced build with a transformer in a separate enclosure so there’s no ground loop breaker necessary. Thanks FA this makes sense now.

nattonrice, it’s ok, I’ve got loads of silly questions to come. Stay tuned
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post #6 of 14
7/26/09 at 6:46am
Quote:
Originally Posted by johnwmclean View Post
Actually I was getting confused, I have input pin 1 of the Beta22 connected to ground signal and chassis as per amb recommendation for a balanced build with a transformer in a separate enclosure so there’s no ground loop breaker necessary. Thanks FA this makes sense now.

nattonrice, it’s ok, I’ve got loads of silly questions to come. Stay tuned
Pin 1 connected to both signal and chassis ground? That doesn't sound right.
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post #7 of 14
7/26/09 at 6:48am
Quote:
Originally Posted by johnwmclean View Post
nattonrice, it’s ok, I’ve got loads of silly questions to come. Stay tuned
Hehe I'm going to milk off your answers that you get and pass off the impression that I'm a genius diy'er
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post #8 of 14
7/26/09 at 6:55am
Quote:
Originally Posted by MrMajestic2 View Post
Pin 1 connected to both signal and chassis ground? That doesn't sound right.
I think that's correct for amps that have no live power in the chassis, signal ground is connected to the chassis. Only amps that have live power wiring should have earth ground connected to the chassis and the signal ground isolated from the chassis ground via ground loop breaker.
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post #9 of 14
7/26/09 at 8:41am
Quote:
Originally Posted by FallenAngel View Post
I think that's correct for amps that have no live power in the chassis, signal ground is connected to the chassis. Only amps that have live power wiring should have earth ground connected to the chassis and the signal ground isolated from the chassis ground via ground loop breaker.
There are no "rules" that are universally followed when it comes to this stuff, which often causes problems when equipment are interconnected. What FallenAngel describes is what I recommend.

The Rane notes says to only connect the XLR pin 1 to chassis rather than signal ground, but that refers to pro equipment with floating differential inputs and outputs. A balanced amp made up of separate "hot" and "cold" amps (such as a 4-channel β22) require a signal ground reference, so pin 1 needs to be connected to the amp's signal ground.
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post #10 of 14
7/26/09 at 7:58pm
And since you're building your entire system, might as well follow a "universally followed rule" that works.

To that regard, I've had to completely butcher my Melos Maestro to remove the direct connection of signal ground to chassis and earth ground to chassis via varistor. Got it quieter once the entire system followed one rule.
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post #11 of 14
7/26/09 at 8:16pm
On my Buffalo 24 I have pin 1 hooked up to ground on the DAC and it's worked flawlessly.
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post #12 of 14
7/26/09 at 9:01pm
Thread Starter 
Quote:
Originally Posted by FallenAngel View Post
And since you're building your entire system, might as well follow a "universally followed rule" that works.

To that regard, I've had to completely butcher my Melos Maestro to remove the direct connection of signal ground to chassis and earth ground to chassis via varistor. Got it quieter once the entire system followed one rule.

Indeed, I’ll do the same with my builds - this making a lot more sense now.
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post #13 of 14
10/19/09 at 7:33pm
Quote:
Originally Posted by FallenAngel View Post
I think that's correct for amps that have no live power in the chassis, signal ground is connected to the chassis. Only amps that have live power wiring should have earth ground connected to the chassis and the signal ground isolated from the chassis ground via ground loop breaker.
Quote:
Originally Posted by amb View Post
There are no "rules" that are universally followed when it comes to this stuff, which often causes problems when equipment are interconnected. What FallenAngel describes is what I recommend.

The Rane notes says to only connect the XLR pin 1 to chassis rather than signal ground, but that refers to pro equipment with floating differential inputs and outputs. A balanced amp made up of separate "hot" and "cold" amps (such as a 4-channel β22) require a signal ground reference, so pin 1 needs to be connected to the amp's signal ground.
So, I'm sketching out the block diagram for a 4-board JISBOS-based preamp/headphone amp. Ala:


I still have to add the power supply and the grounding scheme. Should I be following FallenAngel's convention for grounding layout?
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post #14 of 14
10/19/09 at 8:52pm
I think that would be amb's convention as that's likely where I read it some years ago.
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