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Grounding box in lieu of cable to earth?


lordvader82
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Hey all,

 

I recently completed a passive, TVC based preamp. However, it seems to pick up noise like no-body's business.

If I grab a wire, and touch one end of the wire to the preamp chassis, and the other end to the chassis of an earthed component, the noise completely goes away - so I definitely need to ground the chassis.

 

However, even if I add a grounding post (eg - a brass binding post), I don't really anything earthed to plug the other end into - unless I modify another chassis.

So, do grounding boxes such as these ( https://www.ebay.com.au/itm/282724242692?chn=ps&mkevt=1&mkcid=28 ) fill a void where direct access to an earthing point is unavailable?

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All grounding boxes (Entreq, Nordost etc) warn that they are not a substitute to the primary Earth. Save your money and make a Ground Cable to connect to another components chassis ground connector.

Be worth having a look at the grounding in your Pre-amp.....turn power off though before looking!

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why don't you just connect the two chassis to either power amp or source (if one of those is grounded)?

 

 

 

 

 

54 minutes ago, lordvader82 said:

So, do grounding boxes such as these ( https://www.ebay.com.au/itm/282724242692?chn=ps&mkevt=1&mkcid=28 ) fill a void where direct access to an earthing point is unavailable?

They do nothing.

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1 hour ago, lordvader82 said:

Hey all,

 

I recently completed a passive, TVC based preamp. However, it seems to pick up noise like no-body's business.

If I grab a wire, and touch one end of the wire to the preamp chassis, and the other end to the chassis of an earthed component, the noise completely goes away - so I definitely need to ground the chassis.

 

However, even if I add a grounding post (eg - a brass binding post), I don't really anything earthed to plug the other end into - unless I modify another chassis.

 

Is the pre-amps chassis connected to signal ground in the pre-amp?  If not, give it a try.  I take it there is no power to the pre-amp?  So no earth from a mains socket?

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The preamp has 12v dc for relays and a remote, but yeah, no mains earth.

 

I'll try connecting signal to the chassis before I drill more holes.

 

If that doesn't work, what are strategies for connecting to an earthed chassis that don't require adding a binding post to that chassis too?

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3 hours ago, lordvader82 said:

I recently completed a passive, TVC based preamp. However, it seems to pick up noise like no-body's business.

 

It does that because, as a passive preamp ... it doesn't have a case which is mains-earthed.

 

3 hours ago, lordvader82 said:

However, even if I add a grounding post (eg - a brass binding post), I don't really (have) anything earthed to plug the other end into - unless I modify another chassis.

 

You mean ... none of your components use a 3-wire mains cord (which would have the case connected to mains earth)?  Truly bizarre!  :o

 

3 hours ago, lordvader82 said:

If I grab a wire, and touch one end of the wire to the preamp chassis, and the other end to the chassis of an earthed component, the noise completely goes away - so I definitely need to ground the chassis.

 

What I would suggest is:

  1. add a ground post to the back panel.
  2. make sure this truly connects to the case metal - iow, scrape or grind away the paint/anodising in an annulus around the hole for the post and use a lock-washer under the nut.
  3. then make up an earth wire which has:
  • a banana plug or a spade at the ground post end
  • and a mains plug at the other end.  The wire connects just to the earth pin in the mains plug.

Simples!  :)

 

Andy

 

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2 hours ago, lordvader82 said:

The preamp has 12v dc for relays and a remote, but yeah, no mains earth.

 

I'll try connecting signal to the chassis before I drill more holes.

 

If that doesn't work, what are strategies for connecting to an earthed chassis that don't require adding a binding post to that chassis too?

No need to add a binding post.  You could just attach a wire via an eye or spade connector to one of the chassis screws on the earthed unit.  I have an alligator clip on my turntable ground wire and just grab on to the closest chassis screw.  Does the job.

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4 hours ago, lordvader82 said:

 

That idea (mains cable with an earth wire) doesn't sound like it'll pass any electrical tests...

 

 

Ummm ... you're not connecting to "the mains" (Active or Neutral) - only to earth.  So it's not a 'mains cable' - simply an 'earth cable'!  Because that is not a standard thing to do ... I doubt it is even mentioned in the Electrical Standards - but I will be very interested to hear what someone who knows the standards, thinks about it.  :thumb:

 

1 hour ago, RoHo said:

No need to add a binding post.  You could just attach a wire via an eye or spade connector to one of the chassis screws on the earthed unit.  I have an alligator clip on my turntable ground wire and just grab on to the closest chassis screw.  Does the job.

 

Sure, that will do the job - but it's a pretty crap implementation, IMV.  :(

 

Andy

 

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5 hours ago, andyr said:
  • and a mains plug at the other end.  The wire connects just to the earth pin in the mains plug.

 

I have purchased from Puritan Audio there Ground and RouteMaster. I to run a passive pre and this gives the option of connecting to grounding box via RCA , XLR, spade etc.

http://www.puritanaudiolabs.com/products/ground-master/

Have been delaying setting this up as the recomended grounding post requires some digging and some more. My understanding is this will give the best result. 

I think (but never asked) they provide a wire to a mains plug option for people in apartments.

It sounds like a good solution all be it a temporary one.

Does it matter which GPO circuit you put it on? If you had 2 or more within the house wiring.

 

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8 hours ago, Artnet said:

 

It sounds like a good solution all be it a temporary one.

Does it matter which GPO circuit you put it on? If you had 2 or more within the house wiring.

 

 

My view is that any GPO will do.  However, it's possible one on the same circuit as the preamp may be advantageous.

 

Andy

 

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Well some success I hear.

Small but noticeable gain in clarity to sound stage mostly top end but a softening not so harsh. Did this before Beer o'clock which in Melbourne these days is earlier and earlier.

 

Recommend covering all unused RCA's with Oyaide MWA-RC RCA Jack Cover this was the greatest help in quietening down the Passive Pre but they help on everything I think.

 

The Puritan Audio labs Route master is easy to connect all your components with and the Ground master has controversially some kinda magic in it.  Connecting it via wire and plug see pic,  does some cleaning up!!

This is plugged in to the nearest GPO at the moment,  the another circuit is 7 metres away or more,  so feel I should go out the window and dig and install an earth rod for a better comparison.

20210916_163302.jpg

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