Dedicated power to audio equipment

[HIFI]

I have two 20amp lines running to my audio room.

 

First question . . . The electrician ran separate grounds for each circuit. Was this the correct wiring or should both circuits for dedicated audio share ground?

 

Second question . . . It was suggested that the Mac mini be plugged in (ac power) to another circuit to help shield noise to audio system. Was this good advice?

 

Thanks in advance for helping.

[pooger]

Yes on both. The reason for independent grounds is to have digital equipment on one circuit and analog on the other. (Of course, if the analog has a switching supply in it, then it gets considered digital.) Basically to keep as much digitally derived noise away from the analog equipment. If you can have your computer, along with anything else that has a switching supply (say a hard drive or other peripheral) in a general house circuit (where there's already hash from refrigerators, etc.) that helps keep the dedicated digital circuit cleaner also.

[HIFI]

I think I want to clarify . . .

 

I currently have my Mac connected to non dedicated audio power.

 

I have two 20 amp lines run just for audio. Should these lines share ground? I have one amp plugged in to one circuit and second amp along with all front end equip plugged into to second line.

 

As a follow up question my DAC is part of my front end and therefore plugged into dedicated audio AC lines. Currently FireWire connection from DAC to Mac. Any issues I might address?

 

Thanks

[Deaf Cat]

Hope you don't mind another question, here.

 

When you say dedicated, where does the dedicated line start from?

Is it from the existing fuse box/consumer unit?

So a 20A fuse/rcd/rcbo run for SMPS stuff and another one for linear PSU powered stuff?

 

Or is there/could/should there be a dedicated consumer unit for audio stuff, and use the original house consumer unit for SMPS?

 

Thanks :-)

[coxhaus]

I think dedicated circuits mean they run from your breaker panel whether it is the master panel or the main panel does not matter.

 

A couple of things to check for better sound is to make sure you have an eight foot copper ground rod connected to your master panel for ground. Here in Texas where it gets hot without rain in the summer time you might want to water the ground rod a little when extremely dry. Watering seems to help.

 

The other thing to check for is your house power feed to and from the main breaker to the pole feed. I upgraded mine because it was old and too small. It was sized in the 1960s when electrical loads were smaller. I had 100 amp wire feeding a 150 amp main breaker box. I now have a 250 amp master breaker box with 300 amp wire. I opted for larger copper wire as I think it was less than $200 more.

[HIFI]

Hope you don't mind another question, here.

 

When you say dedicated, where does the dedicated line start from?

Is it from the existing fuse box/consumer unit?

So a 20A fuse/rcd/rcbo run for SMPS stuff and another one for linear PSU powered stuff?

 

Or is there/could/should there be a dedicated consumer unit for audio stuff, and use the original house consumer unit for SMPS?

 

Thanks :-)

 

I have two 20amp lines running from my main breaker box. I use these to lines for amps, preamp, DAC,CD player,turntable.

[bluesman]

The electrician ran separate grounds for each circuit. Was this the correct wiring or should both circuits for dedicated audio share ground?

It's unlikely that you have truly separate ground circuits for each line. You have one house ground at the main breaker panel. While every outlet / duplex / plugmold etc connected to a breaker in the panel has a "separate" ground through its own Romex feed, they're all tied to the same actual grounding point. Unless you have a separate panel for each circuit, fed by a separate drop and having a separate ground, every outlet in your house shares the same ground point.

 

So how can you have a ground loop between or among components that are all "grounded" to the same point? The answers are in the finite resistances of all those wires and the different ways in which circuitry may be "grounded". If there's any electrical potential at all between two "grounds" (grounded chassis, etc), current can flow and generate noise. Each Romex run has enough resistance to set up an electrical potential between the outlet it powers and true ground, even if in millivolts or less. And where there's potential plus resistance in a complete circuit, there's current flow (E = IxR).

 

I found a different kind of problem in my own house (which we designed and built, so this was an oversight on my part even though the engineer, builder and electrician should each have predicted and prevented it). Several of the circuits in our house are run side by side within one side of the main I-beam that supports the main floor. Each one induces a current in the rest - so when shutting off breakers to "modernize" our duplex outlets (yes, that's one of those compromises we discussed in the "why would a man ever marry" thread), I was shocked (pun intended) to discover potential in the outlets I thought I'd shut down. I assumed the breaker was faulty and called my electrician (not the one who did the construction) - and he figured out what was going on. My test lamp did not glow in the outlet, so there's not enough oomph to actually generate any significant current flow. But man did it tingle when I touched it.

 

Fortunately, the wiring to my audio panels (2 plugmolds, each on its own 20 amp circuit) run directly from the panel (which is directly below them) and not in the bundled batch.

[HIFI]

Here is what I know . . .

 

I had an electrician run two lines sharing one common ground and then had that ground fixed, in ground, to a dedicated ground rod. I did not like the noise that I was getting from appliances and certain lights so I asked electrician, who knows nothing about audio, to help me fix. We did a temporary bypass going straight to power line in, other side of consumer breaker box, with same noise outcome. He then ran a second ground for second dedicated circuit because I thought that was correct. I am just wondering did I make a bad suggestion.

 

My original question is still should I have separate grounds or combined grounds for the aforementioned dedicated AC lines for my audio room.

 

Hope this is helpful in helping me.

[Speedskater]

The everything anyone needs to know about AC power wiring and Audio Video Systems:

 

**************************************

"Power White Paper" from Middle Atlantic.com

 

http://www.middleatlantic.com/pdf/PowerPaper.pdf

 

**************************************

The Jim Brown of Audio Systems Group white paper

 

"Power and Grounding for Audio and Audio/Video Systems"

http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

 

****************************************

The new 2012 Bill Whitlock paper (PowerPoint plus text)

"An Overview of Audio System Grounding and Interfacing"

by

Bill Whitlock, President

Jensen Transformers, Inc.

Life Fellow, Audio Engineering Society

Life Senior Member, Institute of Electrical & Electronic Engineers

http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

 

*************************************************

The older 2005 Bill Whitlock of Jensen Transformers Seminar paper (more text less PowerPoints)

 

http://www.jensen-transformers.com/an/generic%20seminar.pdf

 

*********************************************************

I'm not sure why some of the links aren't links?

[bluesman]

My original question is still should I have separate grounds or combined grounds for the aforementioned dedicated AC lines for my audio room.

I don't think it matters - but, as you found out, you have to try different things to see what works in your own location. Two grounds with two connections could actually set up electrical potential between the two at your equipment location, making ground-related hum a reality if source and/or preamp is on one and amp on the other. On the other hand, a standard setup like mine and most others can also result in potential between the ground pins on different outlets. As the noisy stuff (refrigerators, HVAC circulating fan motors etc) is all on separate lines with separate breakers (even though they all share a common house grounding point), I'm blessedly free of noise in my audio lines (as far as I can tell, anyway) despite a "common" ground point for all.

 

It seems intuitively right to separate all audio circuits and their ground point(s) from the rest in the house, as electrical noise (whether induced by adjacent lines or by emissions from devices / motors etc) would be isolated from your audio feeds. But I don't think there's a single or simple answer that applies to all.

[Speedskater]

[................................]

A couple of things to check for better sound is to make sure you have an eight foot copper ground rod connected to your master panel for ground. Here in Texas where it gets hot without rain in the summer time you might want to water the ground rod a little when extremely dry. Watering seems to help.

[....................................]

 

That rod in the dirt has nothing to do with audio quality! It's there for safety during thunderstorms or power company high-voltage failures. Every good paper or book on the subject has the information in the opening sections.

[Speedskater]

[.........................]

I found a different kind of problem in my own house (which we designed and built, so this was an oversight on my part even though the engineer, builder and electrician should each have predicted and prevented it). Several of the circuits in our house are run side by side within one side of the main I-beam that supports the main floor. Each one induces a current in the rest - so when shutting off breakers to "modernize" our duplex outlets (yes, that's one of those compromises we discussed in the "why would a man ever marry" thread), I was shocked (pun intended) to discover potential in the outlets I thought I'd shut down. I assumed the breaker was faulty and called my electrician (not the one who did the construction) - and he figured out what was going on. My test lamp did not glow in the outlet, so there's not enough oomph to actually generate any significant current flow. But man did it tingle when I touched it.

[......................]

Whatever your problem was - it was not not induced current from another circuit.

Mike Sokol has an excellent paper on troubleshooting this type of problem.

 

[h=1]Failures in Outlet Testing Exposed[/h] Jul. 15, 2013

Failures in Outlet Testing Exposed | Contractor content from Electrical Construction & Maintenance (EC&M) Magazine

[coxhaus]

The worst ground problems I have had 15 or 20 years ago were related to cable and SAT disk connections in that they had their own lightening grounds which created a multiple ground situation causing a low hum. I had to lift the ground on these devices to get rid of the hum. The cable was the worst as I wanted cable FM. As soon as I disconnected the cable the hum went away. So I think multiple grounds can be tricky. I would opt for a one ground rod system per house. Once the second ground is in the system it propagates through out as all the grounds are tied together within a house.

 

I now use power isolation for all my equipment in my stereo room. I have 3 220 volt breakers feed my isolation gear.

[bluesman]

Whatever your problem was - it was not not induced current from another circuit.

I don't know your background or level of experience, so I'll just refer you to NEMA engineering department's bulletin #88 on Phantom Voltage (last reaffirmed December 2011):

 

"Due to the high impedance of measuring instruments, a voltage reading may be detected on open conductors where there is no hard electrical connection to a voltage source. Conductors that are installed in close proximity to one another, and are capacitively coupled to each other, can cause this a.c. voltage reading. Such a reading could be 2 or 3 volts, or it may be as high as the voltage on the adjacent conductors. This is what is referred to as a “phantom” voltage...[a] 50 foot run may produce a pronounced capacitance effect whereas a one foot sample may not produce any."

 

The run of bundled Romex along the beam in my basement is about 50' long.

 

Phantom voltage can't harm you, but I definitely felt a tickle in my finger when I first bridged the bare wire ends (and I wasn't going to hold on to see if it was harmful...)

[Savage]

I would encourage listening tests. There are some good places to start, digital/analog as mentioned above but don't completely write-off mixing some of these together if your ear agrees.

 

I found the mac and usb converter much less noisy than expected with the latter actually sounding better on the analog circuit. The mac made little difference where it was placed...not what I was expecting at all.

[Deaf Cat]

So, a breaker per piece of equipment, overkill?

 

My house breaker box is in the stair cupboard, easy enough to come of the incoming mains to another breaker box, 90% of my stereo stuff is in the stair cupboard, all nice and close, no floors to come up, all cables run surface etc.

 

I was thinking one rcbo for music pc, another for pre/dac, another for top end amp, another for bass monos, thinking being the word, as I know rcbo's are nice and safe but running from an rcbo direct to the power input on the amp...

 

As far as I am aware, (needs more research) how my house is wired, I can't go for a copper rod in the ground, just in case there is a fault somewhere in the neighbour hood, and then all others in the neighbourhood will be using my earth... :-o

[sandyk]

FWIW, connecting the shield of a DTV coax at a splitter under the house to a separate earth stake on the shady side of the house at a previous address ,fixed problems due to fridge door light and motor starting up etc.

It never hurts to try additional earthing measures.

Regards

Alex

[Speedskater]

'bluesman' at first I was going to describe "Phantom Voltage" but then I read in your post:

But man did it tingle when I touched it.

"Phantom Voltage" does not cause tingling any greater than a static electricity tingle.

 

Your post has a much better description "Phantom Voltage" than mine ever could.

 

By the way this "Phantom Voltage" is a very different thing than the "Phantom Voltage" that powers good microphones.

[sandyk]

Tingling is often the result when SMPS powered gear is connected / disconnected to an earthed power amplifier.

The voltage readings can be as high as half the mains voltage from the SMPS powered device.

It is due to the typical low value, high voltage capacitor(s) connected between the primary and secondary sides of the SMPS PSU.

[bluesman]

"Phantom Voltage" does not cause tingling any greater than a static electricity tingle

Right - but when you're absolutely not expecting it, even that can be pretty shocking.

 

[Booster MPS]

Right - but when you're absolutely not expecting it, even that can be pretty shocking.

 

 

I find your light hearted take on the dangers of electricity re Volt ing.

[bluesman]

I find your light hearted take on the dangers of electricity re Volt ing.

Ohm my! (Sorry - like the choke said to the power supply, I couldn't resist...)

[Allan F]

Ohm my! (Sorry - like the choke said to the power supply, I couldn't resist...)

 

If you people don't stop this nonsense, you will be severely pun-ished!

[bluesman]

If you people don't stop this nonsense, you will be severely pun-ished!

Aw, c'mon Allan - we just need an outlet for our energy. Otherwise our circuits will get board.

[Jud]

FWIW, connecting the shield of a DTV coax at a splitter under the house to a separate earth stake on the shady side of the house at a previous address ,fixed problems due to fridge door light and motor starting up etc.

It never hurts to try additional earthing measures.

Regards

Alex

 

Must have taken a lot of wire to run all the way to your previous address!