Audio Component Grounding and Interconnection - Page 3

21st April 2010, 12:00 PM
David Davenport diyAudio Member Join Date: Jun 2004 Location: Raleigh North Carolina	Audio Component Grounding and Interconnection This article focuses on audio system design for the DIY enthusiast implementing a stereo system for home use. There is a lot of information available for designing audio circuits, but precious little on interconnecting those circuits into a total audio system to achieve maximum performance.... Click here to read the entire article Last edited by Variac; 2nd April 2011 at 12:07 AM.

29th September 2010

jcx

diyAudio Member

Safety Codes and consumer product Standards are not necessarily logically consistent

if Reinforced/Double insulated mains xfmr, internal wiring is followed there should be complete freedom in what to do with metallic cases and outlet protective earth

further in Intrinsically Safe circuit design which keeps chemical plants from exploding diodes used within their continuous ratings are only assumed to fail shorted - with 2 redundant paths 2 cross connected bridge rectifiers would be accepted in this much stricter safety standard as an "infallible" connection for safety analysis

7th October 2011

Skorpio

diyAudio Member

First of all: Thank you for a very good article!

I am planning a preamplifier based on the Figure 4.2-3 grounding layout. When unbalanced in- and outputs are used all their shields must be returned directly to the main star ground.

If all in- and outputs are placed close (8 RCA connectors isolated from chassis), could their grounds be interconnected with wire maling the main star? Or must each RCA ground be seperately wired to a common star point?

7th October 2011

David Davenport

diyAudio Member

Hi Skorpio,

Think of two things: First is current loops and second is common impedance coupling.

For the inputs, you will have a loop between each input unit's chassis through the interconnect cable to the preamp chassis and back to the input unit chassis through the power cable. However, there will be signal current flowing in a loop when that input is selected. Therefore, since only one is selected at a time, you can share a connection between the input jack field and the main star ground.

There will be current flowing in the output grounds whenever there is music playing. You don't want to mix this output ground current with the input ground current by common impedance coupling, so the ground connection between the output jack and the main star ground should be separate from the ground connection between the input jacks and the main ground connection.

Dave

8th January 2012

Skorpio

diyAudio Member

Hi again,

Since most of the chassis current origins from capacitive or magnetic coupling from the mains transformers, could it be an advantage to put all the mains transformers (except for power amp) in a common chassis, and by this holding the low level chassis free of these error/mains return currents?

9th January 2012

David Davenport

diyAudio Member

Hi Skorpio,

While there may be a small improvement in shielding, I don't think it matters much from a practical matter.

The current in the chassis is not a problem for the signal assuming that there is no signal current in the chassis.

Dave

9th January 2012

Skorpio

diyAudio Member

Thank you David!

17th March 2012

krokkenoster

diyAudio Member

Okay some of you guys have aqll the knowlege to criticise but I wish I had this article way back in 1964 when I seriously started to meddle with electronics. Remember them verydangerous AC/DC tube type equipment? I had some nasty shocks from them as our mains is 245 volts and this bites till I got an isolating transformer. battled with this same problems and had to battle for months on end as I was the only one to ask myself and the basics was to me unknown. I only solved problems by pure luck and was unable to work out for myself what went wong! Thanks for a super article.

19th March 2012

SoNic_real_one

diyAudio Member

Quote:

Second, use a shielded twisted pair for the interconnect cable, with one of the wires in the pair (as well as the shield) being the signal reference

Actually the correct solution IMO is the twisted pair inside a shielded cable, with the shield connected just to the source end star ground.
Any stray fields picked by the shield will be returned to ground, it doe snot create ground loops, all while signal ground does not pick any stray fields.

19th March 2012

David Davenport

diyAudio Member

As I mention in the article, there is controversy on whether to connect the shield on one end or both ends, with compelling arguments for both approaches. I won't argue for one or the other, but vote for whichever works for you

Dave

24th March 2012

SoNic_real_one

diyAudio Member

Haha, I did. Some 28-30 years ago

Shield at one end. Twisted signal/ground inside.