[Folsom]

Correct.  My TT's aluminium chassis is connected to mains earth.  So is the (separate) aluminium plate which the motor is bolted to.  But the 4 signal wires from the cartridge don't touch either of these pieces of metal. 


Regards,

Andy

The turntable's signal has to reference the ground, somewhere, be it through AC power, signal, whatever. The path can become too long and disrupted. (I just fixed this on my own system)

[andyr]

The turntable's signal has to reference the ground, somewhere, be it through AC power, signal, whatever. The path can become too long and disrupted. (I just fixed this on my own system)

Mmmm, let me try and explain, SA (sorry, the setup is so obvious to me, I can't understand anyone not 'getting it'?  ).

1. The turntable has no signal ... the cartridge does.
2. The cartridge has no connection to ground - it simply has 4 wire connections going to the phono stage:
 - L & R channels
 - the 'signal' wire and the 'ground' wire on each channel.
3. The 'ground' wires in the phono cable pass the 'signal ground' to the phono stage circuit.
4. The phono stage signal ground has no connection with the phono stage case - which is connected to mains earth.
5. The phono stage signal ground is then connected to the preamp signal ground, via the interconnect which joins them.
6. Again, the preamp signal ground has no connection to the preamp case - which is connected to mains earth.
7. The preamp signal ground is then connected to the power amp signal ground, via the interconnect which joins them.
8. The power amp signal ground has no connection with the power amp case - which is connected to mains earth.
9. Again, the power amp signal ground (and PS ground) has no connection to the power amp case - which is connected to mains earth.
10. The power amp speaker terminals are then connected to the speakers.

Simples!   


Regards,

Andy

[jea48]

Mmmm, let me try and explain, SA (sorry, the setup is so obvious to me, I can't understand anyone not 'getting it'?  ).

1. The turntable has no signal ... the cartridge does.
2. The cartridge has no connection to ground - it simply has 4 wire connections going to the phono stage:
 - L & R channels
 - the 'signal' wire and the 'ground' wire on each channel.
3. The 'ground' wires in the phono cable pass the 'signal ground' to the phono stage circuit.
4. The phono stage signal ground has no connection with the phono stage case - which is connected to mains earth.
5. The phono stage signal ground is then connected to the preamp signal ground, via the interconnect which joins them.
6. Again, the preamp signal ground has no connection to the preamp case - which is connected to mains earth.
7. The preamp signal ground is then connected to the power amp signal ground, via the interconnect which joins them.
8. The power amp signal ground has no connection with the power amp case - which is connected to mains earth.
9. Again, the power amp signal ground (and PS ground) has no connection to the power amp case - which is connected to mains earth.
10. The power amp speaker terminals are then connected to the speakers.

Simples!   


Regards,

Andy

Yes because I believe you said all of your audio equipment AC power wiring is doubled insulated and equipment chassis does not need/use the safety equipment grounding conductor.

I do find it odd you did not mention if the tone arm on your TT  has a ground wire that connects to the phono preamp grounding post.
Jim

 Edit: 11/14/2013

LOL, I just reread my response to andyr post. It is obvious I misread what he posted.
andyr clearly states his audio equipment uses the safety equipment ground.
My bad.

If the AC power wiring of the audio equipment was indeed double insulated the signal ground would be connected to the chassis.
 

[rollo]

Could it just be a loose connection somewhere like the duplex outlets. For quite some time had a hum from the right channel only. It was a loose ground connection at the outlet. Could be that simple. Take a look.


charles

[mrhyfy]

are there any non-polarised ac plugs in your setup??  If so , trying swapping polarity on them.

[andyr]

Yes because I believe you said all of your audio equipment AC power wiring is doubled insulated and equipment chassis does not need/use the safety equipment grounding conductor.

I do find it odd you did not mention if the tone arm on your TT  has a ground wire that connects to the phono preamp grounding post.
Jim

It wasn't me who said that, Jim.  All my equipment has the case connected to mains earth, via the earth pin on the IEC socket.

In my last system, yes, the arm had a ground wire which connects to the phono stage grounding post (which is connected to the case ... and therefore mains earth.)  But this ground wire does not touch either of the signal 'ground' wires coming from the cartridge - it is there simply to ground the arm.

In my current TT, there is no such earth wire - although the TT chassis is connected to mains earth, via the motor PS.


Regards,

Andy

[mcallister]

mcallister,

I have tried to follow your thread and have a few questions.

How many 15 or 20 amp 120V branch circuits are used to feed the audio system? (Not counting the two 30 amp 120V branch circuits for the subs.)

If I understand correctly each active danley speaker has it's own power amp and thus each is powered by a 120V cord and plug. Is that correct.
All plugged into and fed from one branch circuit? Or fed from several?

Here are just a few Links for you to read.

http://www.aes.org/sections/pnw/pnwrecaps/2005/whitlock/whitlock_pnw05.pdf

http://www.exactpower.com/elite/assets/pdfs/theTRUTH.pdf

http://www.epanorama.net/documents/groundloop/basics.html

http://www.jensen-transformers.com/an/an004.pdf

Sorry for the late replies.

I have one dedicated 20 amp line powering the LCR speakers, and the components. Then I used the existing 20A line that was in the house for the surround speakers and projector. Half of the rooms lights and projector are also on this line. (I plan in building a dedicated HT room in the future with dedicated lines for everything but it will be a ways down the road).

But yes each danley speaker has its own amp (speakerpower digital amps). With the from LCR on the newly added dedicated line and the 4 surrounds on the existing line.

[mcallister]

And equipment that has the signal ground directly connected to the equipment ground chassis ground sometimes is the cause of ground loops and hum.

Take a look at the back power IEC inlet of the OPs Integra DHC 80.2.
http://integrahometheater.com/model.cfm?class=Preamplifier&m=DHC-80.2&p=i
 No equipment ground pin. The equipment is built using double insulated AC power wiring. Only the signal ground is connected to the chassis.

Can the Integra DHC 80.2 pass through a ground loop from an offending piece of equipment like an active speaker through the common signal ground of the pre/pro to another or other active speakers connected to the pre/pro? You bet if the amp uses an equipment ground and the signal ground is connected directly to the chassis. All that is needed is a difference of potential, voltage, to exist from one common equipment ground/signal chassis ground of one amp to the chassis ground/s of the another amp/s and current will flow back to the AC source causing the 60Hz hum.

Problem I have with the OPs hum is the system worked fine in the new house before he added the new branch circuits. He said he hooked the system back up the old way and still had the hum. He had to change something else....
Maybe the OP will check his thread and answer my questions to him in a previous post.

Any suggestions on what to do here about the 80.2?

I did have a friend over to help me diagnose the problem and it seems the loop is being caused by 3 different factors, I couldn't find myself as I would walk from one side of the room then back and couldn't hear the difference without being next to the speaker.

The projector was causing some hum while plugged in......I now have run a extension cord to the power conditioner at the front of the room to clear up that bit of hum

The cable into my time warner cable box was also causing some hum got that figured out

Then the sub amps all cause a good amount of hum through the back speakers when switched on. The two face audio amps have ground lifts on them, when I lift the grounds it helps reduce the hum. The crest amp has no lift and adds a substantial amount of hum when switched on. The crest and the big face audio amps are on the 30 amp line

[mcallister]

are there any non-polarised ac plugs in your setup??  If so , trying swapping polarity on them.

I'm not sure what a non polarized plug is? Is it just a plug without the ground pin? How would I swap the polarity on them?

[mcallister]

My power conditioning has been one of the low points of the system. I've purchased a BPT 10.5 to experiment with. It won't be here for another week or so. Obviously I won't be plugging the subs into it, and I will experiment with plugging the active speakers into it. Any ideas if this will help? Or just wishful thinking?

[mrhyfy]

I'm not sure what a non polarized plug is? Is it just a plug without the ground pin? How would I swap the polarity on them?

A non-polarized plug is a plug with the two spades the same size. Most plugs have one spade larger.  To swap polarity simply unplug it from the outlet ,turn it over and reinsert into the outlet.

[jea48]

It wasn't me who said that, Jim.  All my equipment has the case connected to mains earth, via the earth pin on the IEC socket.

In my last system, yes, the arm had a ground wire which connects to the phono stage grounding post (which is connected to the case ... and therefore mains earth.)  But this ground wire does not touch either of the signal 'ground' wires coming from the cartridge - it is there simply to ground the arm.

In my current TT, there is no such earth wire - although the TT chassis is connected to mains earth, via the motor PS.


Regards,

Andy

Sorry Andy, I misread your post. I clearly had a brain fart moment.

After rereading the post I do have a question for you. Are you sure none of your audio equipment also has the signal ground connected the chassis? Have you checked?

Simple test.
Unplug each component from the AC power and disconnect all ICs from each piece of equipment. With a meter check for continuity from the ground pin of the AC power cord to any RCA jack outer shell, signal ground. No continuity, the signal ground is not connected to the chassis. Continuity, the signal ground is connected to the chassis.

In my last system, yes, the arm had a ground wire which connects to the phono stage grounding post (which is connected to the case ... and therefore mains earth.)  But this ground wire does not touch either of the signal 'ground' wires coming from the cartridge - it is there simply to ground the arm.
andyr


I have a Rega RB 300 arm mounted on a AR TT. The signal ground of the left channel arm wiring is intentionally connected to the arm somewhere within the arm tube by the manufacture.

The AR TT has a ground wire that connects to the metal part/s of the TT and is intended for connection to the phono preamp grounding post. The AR TT also uses the safety equipment ground that is connected to the metal parts of the TT.
The arm is not connected to the grounded parts of the TT.
System is dead quite.



***Warning.***
 If anyone reading my post wants to check if the signal ground is connected internally to the arm using a device/meter to check for continuity NO NOT check from the hot center pin/contact of either the R or L channels to the arm or signal ground of the IC if the cartridge is connected to the arm wiring. You could/will damage the cartridge. Test for continuity should only be checked from the outer shell of the IC RCA plug, signal ground, to the arm.
Jim

[Folsom]

In some cases the grounded arm still has to referance circuit.

You could daisy chain a bunch of spades, hook them under any avaliable screw on all amps, sources, and pre's just to see if it all drops to zero noise. It's not a long term fix, or even short, but it'd reassure what the problem may or may not be.

It'd be possible to build a ground box that doesn't exchange current , just star grounds the system. If that appears like a fix you'd want. You can pm me if you like.

[jea48]

Any suggestions on what to do here about the 80.2?

I did have a friend over to help me diagnose the problem and it seems the loop is being caused by 3 different factors, I couldn't find myself as I would walk from one side of the room then back and couldn't hear the difference without being next to the speaker.

The projector was causing some hum while plugged in......I now have run a extension cord to the power conditioner at the front of the room to clear up that bit of hum

The cable into my time warner cable box was also causing some hum got that figured out

Then the sub amps all cause a good amount of hum through the back speakers when switched on. The two face audio amps have ground lifts on them, when I lift the grounds it helps reduce the hum. The crest amp has no lift and adds a substantial amount of hum when switched on. The crest and the big face audio amps are on the 30 amp line

"Any suggestions on what to do here about the 80.2?"

The problem is not the 80.2, jmho.

The projector was causing some hum while plugged in......I now have run a extension cord to the power conditioner at the front of the room to clear up that bit of hum
What circuit was the projector plugged into before the change?

The cable into my time warner cable box was also causing some hum got that figured out

That one is an easy fix.
Just buy a Jensen Model VRD-1FF  Cable TV RF Isolator. 
Example.
http://www.markertek.com/Video-Equipment/Video-Processors/Video-Noise-Hum-Elimination/Jensen-Transformers/VRD-1FF.xhtml

Then the sub amps all cause a good amount of hum through the back speakers when switched on.
When switched on? That may be caused by the sub amps them self.
You may want to look at the Jensen Link provided below.
 http://www.jensen-transformers.com/


The two face audio amps have ground lifts on them, when I lift the grounds it helps reduce the hum.

Lift the grounds.... The ground lift switches lift the signal ground from the chassis of the amps. It does not lift the safety equipment ground.

 The crest and the big face audio amps are on the 30 amp line

You need to make sure all AC power circuits that are feeding all equipment connected together by ICs are all fed from the same leg, Line, of the same electrical panel.

In an earlier post you said some equipment was connected to a existing 20 amp circuit that feeds Lights and other non A/V system equipment. This circuit too must be fed from the same leg, line.
This branch circuit could be most of your hum problems. A more than likely chance a difference of potential, voltage, is present from the safety equipment grounding conductor of this circuit to the new dedicated circuits.



Member mrhyfy talked about checking for the correct AC polarity orientation in a post.

Reversed AC polarity on the primary side of the power transformer can cause hum.
The reversed polarity could be caused by,

Hot and neutral conductors reversed on the wall receptacle.

Hot and neutral conductors reversed in a home brew or aftermarket power cord.
(Plug may be wired correctly but the hot and neutral conductors of the cord are reversed at the IEC female connector.)

The equipment manufacture did not do his job and did not check for the proper AC polarity orientation of the primary leads of the power transformer before connecting the primary leads of transformer  to the equipment power wiring.

http://www.audioasylum.com/audio/general/messages/449743.html
 AA partial quote from Charles Hansen:
1) Reversed AC polarity -- All power transformers have an inherent asymmetry to their construction. The primary winding comprises multiple layers, so that one lead is connected to the innermost windings and the other lead is connected to the outermost windings. This means that one lead has a higher coupling capacitance to the core of the transformer. Please remember that the AC supply is also asymmetrical, with the neutral lead essentially being at ground potential (assuming there is not a fault in the house wiring). The result is that one orientation will give a higher AC leakage current to the chassis of the amp (and worse sound) than the other orientation.

Not all transformer manufacturers use consistent markings on their transformers so that the correct orientation can be identified, and not all amp manufacturers pay attention to this even if the transformer is correctly marked. The result is that many audio products have a random chance of being correctly oriented. I would have to assume that the amp was modded to achieve the correct orientation, thereby achieving improved sound quality.

The correct way to do this is to swap the transformer leads, and not the connections at the IEC connector. The difference is that changing the leads at the IEC connector will move the power switch and fuse from the hot side of the line to the neutral side. While this *could* increase the liklihood of shock under a very unlikely set of circumstances, in my opinion the service technician *vastly* overstated the hazard that was introduced by this mod.

------ omitted

2) The AC safety ground was disconnected from the amp chassis -- Again, this was likely done to improve sonics. Use of an AC safety ground connected to the chassis on each component *unavoidably* creates a ground loop that will degrade sonic performance. Audible hum can be minimized (but never entirely eliminated) through careful implementation when using single-ended circuitry. Properly implemented fully-balanced systems can eliminate all residual hum, but will still suffer sonic degradation as the AC safety ground acts as an antenna to introduce RFI into the system.

The *only* comprehensive solution is to avoid the AC safety ground and use a two-wire mains connection. To do so *and* meet safety regulations requires what is known as "double insulation", but this is trivially done (as evidenced by all of the cheap Japanese receivers with two-wire power cords).

The difference between "single insulation" (as would be found in the modified ARC amp) and "double insulation" is not all that great. The double-insulated product will have a second layer of insulation in the AC power wiring that will keep the chassis from becoming live should the first layer of insulation fail. The idea is that if there is a million-to-one chance of one layer of insulation failing, then there would be a trillion-to-one chance of both layers failing at the same time.

------ omitted
[/b
End Quote
http://www.audioasylum.com/audio/general/messages/449743.html

http://www.gcaudio.com/resources/howtos/acpolarity.html

[andyr]

After rereading the post I do have a question for you. Are you sure none of your audio equipment also has the signal ground connected the chassis? Have you checked?


Jim

Yes, dead sure, Jim - as phono stage, preamp, active XOs and power amps are all built by me - and that's the way I build them. 

Regards,

Andy

[jea48]

Andy,

Thanks for the reply.
Jim

[Speedskater]

For more on:
'Why standard outlet testing methods fail to reveal reverse polarity bootleg ground miswiring situations'
See this paper by Mike Sokel.  Mike is a member of several pro-audio forums.

"Failures in Outlet Testing Exposed"
Jul. 15, 2013
Mike Sokol | Electrical Construction and Maintenance

http://ecmweb.com/contractor/failures-outlet-testing-exposed   

[andyr]

For more on:
'Why standard outlet testing methods fail to reveal reverse polarity bootleg ground miswiring situations'
See this paper by Mike Sokel.  Mike is a member of several pro-audio forums.

"Failures in Outlet Testing Exposed"
Jul. 15, 2013
Mike Sokol | Electrical Construction and Maintenance

http://ecmweb.com/contractor/failures-outlet-testing-exposed

Wow!    I could say "shocking reading" but instead I will just ask what is wrong with our sparky training that so many of them are so ignorant / slipshod? 


Regards,

Andy

[Folsom]

Nice post Jim,

The sub amplifiers may be getting some DC. If they persist later. But that being said most sub transformers I've seen that aren't too expensive tend to be non-toroid, so they naturally hum. You can dampen them, but to get rid of it you'd have to replace them.

Getting everything on the same panel will reduce most noise, and hopefully equal the grounds well enough that the "loop" that isn't eliminated by this necessarily, will become negligible. The lowest noise floor will be lifting amplifier ground, or start grounding at the equipment, on the rack, so the run is shorter. But that may not be true with a turntable, the preamp for it could need a change; but again potentially negligible.

[Speedskater]

This is from the Audio Precision newsletter last Spring.

Notes from the Test Bench

By Bruce Hofer, Chairman & Co-Founder, Audio Precision

Recently, AP celebrated the 15th anniversary of our custom designed building. Photo albums were displayed showing the construction and the move into our facility back in 1998. (My, how some people have changed in appearance!) Among my many memories of that time, I was reminded of a particularly nasty problem we experienced as we restarted operations in our new production environment.

Almost immediately after moving we began to experience failures of certain bench tests that are performed by our technicians during the course of product assembly and adjustment. After some research, we discovered our new building had some extremely large magnetic fields in the production area, almost as if it was haunted. These fields coupled high levels of hum into our products that were causing the test failures. AP products are designed to reject reasonable levels of stray magnetic fields that would typically be encountered in a lab or production environment. However the magnitude of the fields we faced were at least 20 dB worse.

We ultimately discovered that several of our AC outlets had been wired incorrectly, having their neutral and ground connections swapped. This is a big no-no from the safety viewpoint, but it also caused all of the neutral currents in a particular circuit (outside of our production area) to return through the safety ground connection and ultimately through plumbing and drainage pipes. Some of these plumbing pipes were located in the space directly above our production area while the main drainage pipe was buried directly below; thus our production area was effectively inside of a huge coil. Our electrical contractor was embarrassed but confirmed our diagnosis, and the problem was quickly fixed.

Sometimes one has to think “outside of the box” to correctly perceive or understand a given problem. In this case, our new building plans provided the necessary insight to recognize the inadvertent source of our unwanted magnetic fields (plumbing that formed a coil around our production area). Perhaps you might want to check the neutral and safety ground connections of the AC outlets in your own work space—there could be some ghosts present!

Enjoy this month’s edition of our newsletter…

Bruce