Humming Along To The Pin 1 Problem

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Speedskater

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Re: Humming Along To The Pin 1 Problem
« Reply #20 on: 30 Jul 2015, 05:22 pm »
1) I'm ok with this but in my view that's really a nit.
It's about 'good engineering practices'.
The chassis connection should be near the most sensitive circuits.

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2) This moves away from a star ground centric approach and invites the possibility of the star ground being at a different potential than the chassis. I realize the "earth to chassis" has been a traditional approach. I just don't agree with it. In my view "earth to star" and "chassis to star" (everything to star) preserves both the integrity of the star philosophy while also being safe.
In line with what  barrows wrote.  A star ground is far from a be- all and end-all idea. The AC Safety Ground should not be part of the DC supply, audio circuit chassis connection point. Besides a long Safety Ground wire inside the chassis, just acts as an interference antenna.

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3) Not sure what this accomplishes. Everything to star all the time - no hum.
It's the main part of AES48.

tortugaranger

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Re: Humming Along To The Pin 1 Problem
« Reply #21 on: 30 Jul 2015, 06:04 pm »
It's about 'good engineering practices'.
The chassis connection should be near the most sensitive circuits.
In line with what  barrows wrote.  A star ground is far from a be- all and end-all idea. The AC Safety Ground should not be part of the DC supply, audio circuit chassis connection point. Besides a long Safety Ground wire inside the chassis, just acts as an interference antenna.
It's the main part of AES48.

I think that when you distill all of these last few posts down there's very little substantive difference. If you locate the star grounding point on the chassis in close proximity to the input near where pin 1 is landed right by where the earth safety gets connected that it becomes for all practical purposes a single star ground point regardless of what you call it. To say the AC ground should not be part of the DC supply kind of defies gravity since unless you're designing a floating +/- split DC supply your supply ground will most definitely connect to the AC earth ground. Whether that connection is a few inches over here or over there are differences without material distinction....in my opinion.

Having said all that, let's not turn this into a debate about NEC, AES48 or best engineering practices. We can quibble endlessly around the margins to no good end which is something that happens in excess in audio land.

We tried to step around the pin 1 problem altogether by not connecting them at all and got bit because of that. How could not landing a cable shield (A CABLE SHIELD!!) possibly cause a hum problem? Because some equipment designer on the other end didn't follow good engineering practices and landed pin 1 where it shouldn't be connected. What a PITA!  :thumb:

enser

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Re: Humming Along To The Pin 1 Problem
« Reply #22 on: 4 Mar 2017, 06:41 pm »
2.5 words: jensen iso-max :D