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    Grounding - Some Thoughts

    Peter W.
    Peter W.

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    Grounding - Some Thoughts  Empty Grounding - Some Thoughts

    Post by Peter W. on Wed Nov 30, 2016 10:17 am


    After seeing, and participating in, the discussion on 3-wire cords, and seeing other discussions on grounding in general, I think that relating a few experiences may be useful. First, a few things:

       a) I have always, well, at least since I was 22, lived in houses or apartments with radiators on cast iron risers from a central boiler that was also directly connected to the (copper) water service. Meaning that I have had a good ground available in every room of the house/apartment.
       b) In general, I have linked all my audio components, even those with 3-wire cords from the factory, together and thence to a good ground.   For those components not equipped with an actual ground lug, I have used a spade lug on an exterior screw in some unobtrusive location.
       c) And, just for common sense, kept the path as short as possible.
       d) Using fairly robust fine-stranded copper wire, usually 12-gauge.

    I have never had any hum problems due to this method. And on at least one occasion, when a very-vintage power-transformer chose to fail on a very vintage, very cheap solid-state amp, the fuse blew on the amp rather than giving me or anyone else a shock.

    When I was living and working overseas, our villa had central AC, all ductwork, no suitable, similar local grounds available but the ground in the receptacle (NEMA style). Being the boss, I had our electrician drive a ground rod outside (even though we were in a desert country we were very near the Gulf, so the water table (brackish) was about two meters down). From there, I came up in insulated #8 stranded wire to my work bench, and to the living room for the grounds, one for my hobby, the other for the stereo.
    Point being, after all this, I would not rely on the third leg of a receptacle being always a “good ground”, especially as compared to another receptacle or other local ground such as a water pipe. Nor, these days, would I rely on a water pipe much as with the advent of shark-fittings, PEX, dielectric unions and other devices and materials, continuity is often interrupted.

    And, especially in older installations, BX (armor-flex/MC) cable relied on the exterior armor for the ground, and older NM (Romex) permitted the ground wire to be one gauge smaller than the primary wires. Such grounds are adequate for appliances, tools, and similar, but not so much for audio.

    As things stand right now, I use the heating system standing radiators on black-iron or copper risers, verified all the way to the main municipal water service as grounds for the five operating stereos and my workbench, as described above. No hum issues.

    I very strongly urge individuals who own/operate/maintain audio equipment, especially older/vintage/legacy equipment however well restored to install a separate, high-quality ground rather than rely on the mains ground, which can be problematic or worse. Keep in mind that the tools that verify correctly polarized receptacles and grounds are pretty broad-brush devices, such that resistances of a few dozen ohms will not show as a failure – but could be damaging to equipment, or its users. I know that this might be difficult for renters or apartment dwellers. But in those cases, be absolutely sure to make sure, and be sure, again, that _all_ your equipment is connected to the same ground and not several. And if all your equipment shares the same preferably dedicated circuit, that is even better.

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    Post by sKiZo on Thu Dec 01, 2016 11:39 pm

    I have a 140 foot grounding rod here in the form of a 4" well. I did make sure they strapped the pump either side to maintain a good solid connection.

    Also worth mentioning, a dedicated power circuit for the stereo is a good idea. I ran a line directly to the main buss just for that.

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    Post by wildiowa on Fri Dec 02, 2016 6:37 pm

    I am very basic in my understanding of schematics etc. but I have always been baffled as to the grounding scheme and design logic on the Dynas. Let me explain that all of mine (2 MkIII's and one ST70) were owned by a recording studio/sound company back when they were using A-7 Voice of the Theatres. As a result, for convenience in hooking up a sound system all have been modified with standard 1/4" phone jacks for both input and output. These were rather crudely added by drilling holes into the case and adding the jacks, all grounded directly to the chassis.

    When I dug these amps out again after 30 or so years I decided to replace the caps and made the diode mod but kept the old boards. In firing them up I did get some hum and at that point I was on this board long enough to understand that the grounding situation was very funky on some of the older Dynas. My solution, given the fact each amp had been drilled and the phone jacks added and they were already compromised cosmetically, was to order some ground isolation jacks that have a plastic washer between the case the phone jacks. This keeps them away from a common ground and frankly I don't know if it helps anything or is correct or not or is a futile effort, but it's done.

    I honestly don't use these enough to listen for differences or changes but again, it just always seemed to me that in any amp the chassis was ground. And in a two-wire amp it seems the neutral or white should go to the chassis.  The Dyna seems contrary to this the bias caps wired with the pos to the chassis and the neg to the bias side....what's with that?? And in the two-wire power cord configuration when you talk about running the hot (black) wire to the chassis like I think I have heard some discussion here, isn't that like deadly or something??

    You guys probably all understand this but it seems there are plenty of hum issues and mysteries and exploded caps inserted with the wrong polarity to be mere coincidence for us rookies and amateurs. Not sure if this is easily explained, or needs to be....but....

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    Post by GP49 on Fri Dec 02, 2016 9:29 pm

    wildiowa wrote:And in a two-wire amp it seems the neutral or white should go to the chassis.

    NEITHER side of the mains should be connected to the chassis on a Dynaco amplifier. EVER.

    What would your situation be should your wall outlet be wired backwards? This does a house
    where I was recently checking out the outlets, I found several that the contractor had wired backwards.

    An All-American five tube radio, yes. One side of the mains is connected to their chassis. But they are
    built so that the user cannot touch the chassis...only plastic knobs and controls or other parts that are
    isolated from the chassis and from direct connection to the mains.

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    Post by wildiowa on Fri Dec 02, 2016 9:57 pm

    Yeah I didn't do very well expressing the ground to chassis thing...please no one hook your mains to the chassis. On the Dynas I just put the green ground direct to a star on the chassis when I replaced the old two-wire with a new three-wire power cord. But I did have to think through which polarity I wanted to go to the fuse, power switch etc. on the other two connections...I also have two old Silvertone guitar amps that I have replaced the old power cord with a new three-wire grounded cord and bypassed the death cap and switchable ground. Ya gotta think through the path of the AC before you do some of these changes or you can get knocked on your butt. I have tried to preserve the two-cord vintage setup on a couple of old tube guitar amps but you will inevitably get a blast when your sweaty lips hit a microphone. You just gotta ground those things for your own safety. If your amp is not grounded and the PA is, you got trouble. That doesn't seem to be as big of a consideration with the hifi stuff as we are not handling it...hopefully, except to give it an occasional hug.

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    Post by tubes4hifi on Sat Dec 03, 2016 2:42 pm

    the black wire is HOT, (it's the smaller slot on modern AC outlets) and the white wire is NEUTRAL (the larger slot on modern AC outlets) and the ground wire is usually green.
    the black HOT wire should go thru the fuse and the power switch.

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