#75223 - 03/02/06 04:52 PM
Re: nonstandard power cord on 970?
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Desperado
Registered: 03/21/01
Posts: 14054
Loc: Memphis, TN USA
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The two-prong power connector found on a fair bit of Outlaw's gear (the big amps being an exception in general, as I recall) is pretty common for the industry. How many DVD players have you owned with three-prong plugs? How many cable or satellite receivers? Heck, my TV doesn't even have a three-prong plug. As I mentioned I would think most of the niche Outlaw customer base would have upgraded to a similiar scheme at least for their home theater/listening room. It is probably very common for Outlaw components to be plugged into outlets whose wiring hasn't been touched since the house was built 50, 60, or even 80 years ago. Having grown up in a house from 1927 and owned two houses from the 1950's, I can vouch for the cost and challenges involved in updating to a three-conductor dedicated circuit for home theater. I suspect that far fewer Outlaw owners have made improvements to their wiring than you might think.
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#75224 - 03/02/06 05:32 PM
Re: nonstandard power cord on 970?
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Desperado
Registered: 01/17/02
Posts: 380
Loc: South Weymouth, MA USA
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If your oustside sourced signals aren't grounded at the same place as your incoming electricity to your dwelling you should insit it be done by the installler or signal provider!!! It's a fairly inexpensive procedure. Jim
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#75225 - 03/02/06 06:00 PM
Re: nonstandard power cord on 970?
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Desperado
Registered: 01/14/02
Posts: 1176
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Originally posted by openhelix: If everything is grounded/filtered correctly I really don't see how low voltage signal will bleed over onto AC. Imagine a long coax, both ends of the shield earth grounded. Now send a current through the center conductor, through a load, and back up the shield. Notice that there are two 'return' paths for current, one along the shield, one in the earth. Gounding/filtering won't really help.
_________________________
Charlie
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#75226 - 03/02/06 07:09 PM
Re: nonstandard power cord on 970?
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Gunslinger
Registered: 02/16/06
Posts: 107
Loc: Santa Clara, CA
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That's not what you were explaining above. What you said previously, as I understood it, was a low voltage signal (like cable TV) coming in, hitting a component and somehow finding its way into the AC line. If the LV and HV "parts" are properly isolated then the signals should not interfere/bleed.
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#75227 - 03/02/06 07:28 PM
Re: nonstandard power cord on 970?
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Desperado
Registered: 01/14/02
Posts: 1176
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Originally posted by openhelix: That's not what you were explaining above. What you said previously.... If the LV and HV "parts" are properly isolated then the signals should not interfere/bleed. It's actually precisely the same thing, with more focus on a specific single case the second time. Try this: "Imagine a long coax, both ends of the shield earth grounded. Now send a current through the center conductor, through a load, and back up the shield. Notice that there are two 'return' paths for current, one along the shield, one in the earth." Now imagine that instead of directly grounding our end of the shield, we instead connect it to our cable box. The shield is now connected to chassis ground via the threaded shell connector. Next, we run a signal connector from the cable box to our Pre/Pro, say, an audio left channel RCA connection. That connector may or may not be shielded, but it won't matter, because it's a single ended connection, meaning one of the signal wires is connected to the "shell" connector at each end, and on most devices the shell is chassis grounded. Now the chassis of our pre/pro is grounded thru (yes, indeed!) the ground wire of its' power cord. Thus, current will flow along the cable signal wire, down the chassis grounded signal wire of the low level signals, and out back to the cable ground rod via the devices grounding conductor and thus to the house grounding system to earth. EDIT: I'd like to know what the supposed benefits of grounding would be in a case like this, as per the assertion that Outlaw was "using a lesser connection"; I see it as more of a design choice.
_________________________
Charlie
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#75228 - 03/03/06 05:40 PM
Re: nonstandard power cord on 970?
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Gunslinger
Registered: 02/16/06
Posts: 107
Loc: Santa Clara, CA
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Charlie, is it really worth rehashing a discussion that I'm sure you're read a million times at places like audioasylum, avsforum, etc on 2 vs 3 prong connections? i think not. Both sides of the argument are pretty common knowledge. If you really need a unbiased explanation, here ya go: http://www.gov.ns.ca/enla/electricalsafety/esbadapterplugs.asp Your argument on the RCA cable is moot when you consider the existence of single-ground cables that are only grounded on one side which are fairly prevalent in many analog audio (over RCA) designs. In addition, even in the case of a dual grounded RCA cable, the resistance should be significantly higher over the aluminum chassis versus the copper conductor and since current follows the path of least resistance, it will never enter. Current only takes one path at a time through any given circuit. High relative resistance effectively equals isolation in circuit design, excepting field dynamics which aren't really at issue here. I think we'll just have to agree to disagree. Design choices always have compromises. I see this as one of them. I simply would have liked to see the logic behind the decision. You've given a lot of "maybe" scenarios, but none of it relates to what the outlaws might have been thinking when they made the decision. Gonk's explanation that, in his experience, many homes to outlaw equipment are older and have old-spec wiring seems the best possible explanation. However, I would have liked to see the Outlaws err on opposite side and allow a three-to-two adapter with a grounding lug for 2-conductor systems.
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#75230 - 03/03/06 06:46 PM
Re: nonstandard power cord on 970?
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Desperado
Registered: 01/14/02
Posts: 1176
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A discussion of cheater plugs isn't germane to a discussion of a UL approved device. Originally posted by openhelix: .... moot when you consider the existence of single-ground cables that are only grounded on one side which are fairly prevalent in many analog audio (over RCA) designs. As I explained already, this is a non-issue. In a single ended connection such as an RCA type, ou have a pin and a shell. Even on the cables you describe, the "shell" HAS to have a conductor associated at each end. For example: Shell->Shield->(No Connection) Shell->grounded signal wire->Shell Pin->Floating conductor->Pin Is a fairly typical construction. Note that there is and MUST BE a path from shell to shell for the interface to work. The connection of the SHIELD is not really of interest. Originally posted by openhelix: .... since current follows the path of least resistance, it will never enter. Current only takes one path at a time through any given circuit. Perhaps I didn't understand you before, but I thought you said you were an EE? I assumed that was Electrical Engineer? If this little "fact" were remotely true then only one device on each distribution grid would get power at once. Your neighbor turning on their TV would turn off your water heater. Indeed, taken to it's extreme conclusion electrical devices as we know them would be impossible. This is, to put it plainly, wrong. Current follows all available paths. This is a basic electrical fact. The small current flowing in the path I described proves (using basic algebra and Ohms' law) that there is a voltage also present. The presence of a ground-loop induced current therefore causes noise. But none of that is primary to the discussion. The main thing is that Outlaw designed this unit to not use a grounding conductor and had the realization of that design UL approved. The device is safe, and furthermore, not intrinsically inferior due to this design choice. I appreciate that you want to bow out of this gracefully, and I applaud your intentions to do so, but I'm not going to let you present fiction as fact to further that aim.
_________________________
Charlie
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#75231 - 03/03/06 07:05 PM
Re: nonstandard power cord on 970?
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Desperado
Registered: 01/14/02
Posts: 1176
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Where's Soundhound when you need him, anyway? Jeez.
_________________________
Charlie
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#75232 - 03/04/06 10:42 AM
Re: nonstandard power cord on 970?
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Deputy Gunslinger
Registered: 12/23/05
Posts: 11
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"Makes sense, but I'm sure you're aware of all issues with a standard 2 conductor line. Most modern homes have been built with 3 conductors inbound and three conductors to every outlet"
This statement is a little misleading. Yes, a modern home's electric service has three conductors inbound - one ground, two hot wires (different phases). Each outlet has three conductors, but not the same as the three inbound. A single phase hot wire, plus a neutral and ground, which are tied together at the distribution box. So in reality, only two of the three wires from your electrical service are present at an outlet.
And being an EE (electrical engineer) has little to do with being an electrician.. I'm an MSEE, but wiring my basement addition took a whole bunch of different skills.
dave
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