[Dan Banquer]

GROUNDING PRACTICES IN CONSUMER AUDIO

  As many of us have observed over the years grounding practices in consumer audio have for many of us been a frustrating experience. Compatibility/Synergy are consistently major issues, as well as safety, reducing ground loops, noise and interference. Designers are equally frustrated by this problem. Some of us wish it would go away and others attempt to deal with as best as we know how.  There does not appear to be much of any standardization that I, and many others are aware of.  Many of us who work in the electronics industry outside of audio who have observed the posts from audiophiles, designers and dealers scratch our heads in near disbelief.
  The following is not only an outline for reducing these problems, but a wake up call to this end of the industry. The following is for the application to consumer unbalanced audio, and could well be a possible outline for positive discussion and direction. It is also a way to use Earth Ground to our advantage instead of a problem.
   Chassis Grounding:
   The following is a technique used in instrumentation for low frequency applications.
The chassis will be earth grounded via the earth ground at the three-prong outlet. The audio signal ground contained in the chassis is not connected to the chassis ground. This will require the design to be electrically isolated from the chassis ground which is easily solved by using nylon stand offs to mount pc boards and isolated bulkhead RCA jacks.    (I am going to break this rule later on but bear with me for the moment). The above forces the design to be star grounded at the return of the power supply, which is always good practice to reduce noise and ground loops. However, this does leave the present configuration susceptible to interference from the inputs. This interference can be reduced by the using a simple common mode ac line filter at the AC input and using either a well shielded coax or microphone cable at the line level input. This configuration also poses an additional problem due the fact that we now have two different grounds with two different potentials. In the past I have observed this problem when using a certain brand of rotary switch for a volume control. The rotary switch was not well isolated internally and had enough of a leakage current so that noise was developed when it was used.  Moving to a different vendor with higher isolation devices corrected the problem. I have not observed any problem with standard switches for on off applications or anything similar.
 I have applied this technique to basic audio chain of equipment consisting of an outboard DAC, line level pre amp, and power amps using the chassis and grounding design I outlined above. The transport that I presently use is a modified consumer device and is equipped with a two-prong plug. The system also has an FM tuner and an old pre amp that is used as a phono pre amp. Both of these devices are standard consumer issue with a two-prong plug. I have observed no compatibility issues with the older style units.
  As I outlined earlier I am going to break this rule at one point. The line level pre amp now has a connection from the return of the line stage pre amp power supply to the chassis of the unit. I have now connected earth ground to the analog “center point of the system.” This did not cause a ground loop at all, and to be more precise, for CD playback the inherent ground loops that are typical for unbalanced circuitry simply disappeared. The FM tuner and the old pre amp appear to be unaffected by the center point earth ground. A welcome addition was that the rotary switch that had a leakage problem because of the two different potential levels described earlier no longer had the problem due to center point earth ground.
The use of the system center point earth ground for low frequency applications has been in the textbooks for at least 30 some odd years and has been applied to other low frequency applications. Applied at this level to a simple chain of audio playback equipment. CD playback now has reduced hum and hiss to levels more akin to balanced design than unbalanced design. Playback of FM tuner and Phono pre amp remains unaffected.
One thing that has surprised me relates to the issue of low frequency applications. I was expecting to find problems with the digital portion of this playback chain. I have not found one to date but I think this needs to be investigated further when time allows.
  A note to all of the tweakers who read this: I am not recommending any changes to existing designs; in fact I would discourage it.
  To DIY folks: You may wish to rethink some of your present chassis/grounding schemes.
  To the rest of the industry; this is a subject that not only deserves discussion but an active participation to reach acceptable standards.
  The grounding system described above will not address the problem of toroidal transformers mechanically vibrating due to either DC on the AC lines or as I have observed on occasion, low frequency oscillations.
   Dan Banquer
    R.E. Designs
P.S. I would greatly appreciate it if the following discussion is limited to the issue of grounding only.

[DVV]

Some of what you say should be done is in fact used in some consumer audio equipment, notably by British companies (Arcam,  TAG-McLaren, Boothroyd-Stuart Meridian, Creek, etc). It has crossed my mind more than once that this could be at least a part of the answer as to why British audio usually sounds better than its flashier counterparts from elsewhere, most notably from Japan.

But to be fair, I have come across audio equipment with outstanding grunding schemes, and the odd thing is, it was almost all from Germany. Of the companies I refer to, still active today are Burmester and T&A, while Wega (bought out by Sony in mid-80-es), Loewe (bought out by Philips, now making mostly TV sets), Uher (bought out by Harman International, today of zero significance in audio) and ASC (which I will never get over lamenting, they were way out) unfortunately are no longer around. What is common to all of them is an outstanding amount of time and attention paid to grounding. Hum loops with any of them? You'd be lucky.

Point is, it CAN be done, people DID and DO do it, but this requires much care, attanetion and knowledge and is hardly interesting to anyone rushing to ship out this quarterly new models.

In other words, that the mass industry doesn't do it right is hardly a wonder, but what is worrying is that much of the so-called "high-end" products use very low end, or no end grounding, resulting in performance way below the prices asked.

Cheers,
DVV

[warnerwh]

Would one of you please explain the importance of the main ground at our homes please?  It seems that over time the grounds could become oxidized and be more resistant and may affect our system somehow.  Maybe this is something we should check.  I just did this at my house and the pipe was completely corroded where the grounding clamp made contact.

[Russtafarian]

I have become a big fan of Equitech's balanced power systems.  I have one at home for audio/video and I had my church put one in for their PA/video projection system.  Equitech recommends chassis grounding every piece of gear to their ground.  The result?  No noise, no ground loops, improved audio/video performance.  I couldn't be happier.

[Dan Banquer]

To Warnerh: The main earth grounds should be checked for corrosion every few years. Especially for those of us who live in some very humid environments. This effects your entire house, not just audio.
To Russtafarian: For the modest set up I outlined in  my post those balanced transformers are not needed. For sound reinforcement, the use of the transformer depends on the "quality" of the equipment and the wiring in your church.
  Gentleman: the problems are in the "present state of the art" equipment and improper or corroded electrical wiring.
    d.b.

[warnerwh]

Thank you for your reply Dan. I sanded the pipe and put two fresh clamps on right next to each other and tightened them very hard.  It seems like water pipes would be very susceptible to corrosion especially in a humid environment like where I live.  Maybe some grease like you use on car batteries would be a good idea or possibly some silicon.

[Dan Banquer]

I would definetly recommend that you get an electrician to look at your work, but your on the right track.
                      d.b.

[DVV]

Thank you for your reply Dan. I sanded the pipe and put two fresh clamps on right next to each other and tightened them very hard.  It seems like water pipes would be very susceptible to corrosion especially in a humid environment like where I live.  Maybe some grease like you use on car batteries would be a good idea or possibly some silicon.

Careful with that grease! Yes, in principle, it could improve contacts, but provided it is not subjected to heating, and that there is no overt source of dust nearby.

WD40, the do-it-all spray, is NOT a good solution, not because it won't improve contacts, but because it tends to drip and is very hard to apply, as is any spray, without having it go where it shouldn't.

If you want to push limits, use a compund you can make at home. Take a bottle of eye or nose drops, one with a pipette (the rubber/glass bit that lets you drip drops). Put in one half of vaseline (available at any drug store) and benzine (gasoline), however the preferred type is the kind you can buy in drug stores in small bottles (at least in Europe), but failing that, quality car gasoline will also do. Shake vigorously for 10-15 minutes, until the mixture inside is just a little more liquid than jelly. Apply carefully in small doses over contacts, make VERY sure you don't overdo it, it must not be allowed to drip. After application, that contact will be clean for the next two years, unless it is open to the weather, which as contacts go, it is of course not.

Exactly the same compound is a great cure for crackling potentiometers, rotary or sliders; insert three drops, one at leftomost, one in the middle and one in the rightmost side, rotate/slide for about a minute or two, and forget that pot for the next two years, it will work (or else!).

Cheers,
DVV

[warnerwh]

DVV: the type grease you suggest is available for car batteries and works great in a very harsh environment of heat and moisture.  Just seems that coating the grounding clamp after all is connected that it would stay good much longer and costs nothing.

Forgive my use of "silicon" for what I meant is a silicon sealant that dries like a rubber.  Once on it would last for decades and the contacts would remain perfect. What do I know though as the NEC would surely have done something about corroding ground contacts if it was important.

Forgive my ignorance here but you guys refer to differing ways of grounding our audio equipment as though there's many companies who don't do a very good job.  This would seem odd considering the prices we pay for our gear. Also it appears this is extremely important.  What I'm wondering is why it isn't done as proper grounding would seem to be very inexpensive or is it?

[Dan Banquer]

It's not expensive, and I never found it particuarly difficult either.
I think the industry needs to take a closer look at this "proposal" and standardize.
For line level units I think a switch on the back panel that either connects the audio signal groud to earth or not would help compatibility issues.
                      d.b.

[warnerwh]

Now I'm wondering why the AES hasn't looked at grounding in more depth.  I've dealt with ground loops twice over the years and it's very annoying to have to track down.

[Dan Banquer]

The June 1995 AES Journal is pretty much devoted to it, however most of that is for balanced operation. Reprints are available. Try Reducing Noise in Electronic Systems by Henry Ott, it's one of my "bibles" so to speak. Jensen Transformer also has a lot application notes that you might helpful, but that is also predominatly for balanced operation.
           Hope this helps.
                       d.b.

[DVV]

DVV: the type grease you suggest is available for car batteries and works great in a very harsh environment of heat and moisture.  Just seems that coating the grounding clamp after all is connected that it would stay good much longer and costs nothing.

Didn't know that - thank you for the info.

Forgive my ignorance here but you guys refer to differing ways of grounding our audio equipment as though there's many companies who don't do a very good job. This would seem odd considering the prices we pay for our gear. Also it appears this is extremely important. What I'm wondering is why it isn't done as proper grounding would seem to be very inexpensive or is it?

Nothing ignorant about your question, it's a very reasonable one in light of what was written here.

Yes, Dan and I are in complete agreement on this issue - audio (and other) companies do NOT do a good job of ground. That's by and large, of course there are exceptions.

There are several reasons for this. One is that to get it right you need to experiment a lot, and that ties up people, labs, materials and time, all of which can be summed up with just one word - money. Most companies are unwilling to go any further up the creek than to avoid any overt ground loops.

Another reason are the case materials. Most use sexy thick aluminium front plates, but cheap pressed steel everywhere else. Aluminium is, as metals go, not very given to magnetics, while steel is very much given to magnetics (but it's cheap). Hence, steel will conduct what is known as addy currents, small and even miniscule currents emanating from electronic circuits, airborne radio waves, etc, and while each is of very low power, when added up they tend to produce serious disturbances.

Also, to be honest, manufacturers cannot possibly know in which environment their audio will be used, and I refer to the electrical properties. Will your wall socket REALLY be earthed, or will it just look like it is? What will be the ground potential on it, the one dictated by IEC norms, or something else?

Now, NOBODY can know the answers to all of the above beforehand, but with some time and trouble invested, a designer can produce very credible, even creditable, grounding potential. The key word here "potential", meaning that he has done what is reasonable to expect of him, and by the book. If his product sits in an electrically faulty (no grounding, no earthing, or poor on both accounts) envirnment, that is indeed not his fault, there's nothing he can do about it.

As for audio costing a lot of money, I'm afraid that's no guarantee at all that what needed to be done was indeed done. The days when a high price was a guarantee of anything are long gone, these days a high price is just an indicator of the probability that the job was well done. And this is not only in audio, it's everywhere.

Cheers,
DVV

[JoshK]

I just wanted to confirm I understand this correctly.  You are using a star earth point in the PSU for, let's say, your amp, but that point is floating, not grounded to chassis.   It is only grounded to chassis in the preamp.  Is this correct?

[Dan Banquer]

Yes. I am using Star grounds for all the equipment that is of my design. The only connection to earth is from the return of the pre amp psu to earth.
          Kabish?
            d.b.

[JoshK]

Thanks...makes a lot of sense.  I didn't quite understand the first time I read this many moons ago, since I hadn't much electronic knowledge then, but not it makes sense.

Is there any reason why this scheme wouldn't work for a mixed unbalanced/balanced system (XLR from preamp to amp, RCA for sources)?

[Dan Banquer]

It may or may not. I think it's going to be trial and error here Josh. Remember; there are no real standards for grounding in consumer audio so anything can happen and it usually does.
                    d.b.

[JoshK]

Thanks, that is what I thought, but it seems like you could do it to the same affect if you floated the XLR connectors too. 

[Dan Banquer]

A balanced connection is a differential connection so there is no ground. Pin 1 on the XLR is "shield" or earth ground which should be connected to the chassis of the unit.
                  d.b.

[audioengr]

The only problem with this type of grounding scheme, particularly for manufacturers of DAC's etc.. is emissions.  EMI can be effectively reduced by grounding circuit-boards to the chassis at multiple points.  While I am not a fan of this, sometimes it is necessary in order to pass FCC testing.

The important things that must be addressed with grounding are:

1) safety ground - the chassis must be grounded to "earth ground" of the AC power cord.
2) ESD - grounds or bypass caps must be applied at all signal inputs and outputs in order to minimize Electrostatic discharge effect on the circuitry
3) EMI - In some systems, the circuit board must be grounded at multiple points to the earth ground in order to pass FCC emissions testing.
4) Signal return paths - these are often confused with chassis ground.  I even have modded a Sony 400-disk CDP where some of the signals were forced to flow through the chassis because of a break in the circuit board ground plane.  The break was only connected when the board was screwed to the chassis.  This shows that even large companies make this mistake.  There are instances of changing the chassis from steel to copper and suddenly it sounds better - there were probably signal currents flowing through the chassis, a bozo no-no.
5) Power return paths - power currents should not flow in the chassis either.

In order to comply with the safety ground requirement above, Every component should be tied to safety ground - the chassis ground.  As for tying the DC-common ground to chassis-ground, this should be done in most cases at one point or many points.  Then, in order to break ground-loops, isolation steps take care of this, such as Isolation IC's or pulse-transformers.   If isolation is impossible, or compromises sound quality, then I would agree that floating the DC-common can be a useful strategy.  However, one must be aware that potentials can develop between the ground of the connectors and the chassis, depending on the phase and circuits of the AC wiring.

Steve N.