[guest1632]

hi all,


I got bored, so I decided to check out this problem with my amp.

What prompted this was, at one time, I had a CDPlayer with a nonpolarized AC plug. If I plugged it in one way, the mids would be forward, and I wouldn't have as much detail. The other way, the mids were pulled back a little and the bottom and top were extended with more detail.

So I decided to try this out with my amp. I took one of the half dozen or so power cords from computers, and from the IEC end, back about a foot or so, cut the cord. Then using my RadShack DVDm I then made sure I had continuity between each wire on each end. I then used some wire nuts to fasten this all together. I used a small one on the third wire, so as not to mix them up.

I listened to a song for awhile, and then unplugged the plug from the wall, switched wire sides, and plugged it back in. Listening to the same song and repeating this process, I think! I heard a slight difference. The difference being that it seemed that the top end was perhaps a bit more effortless There wasn't as much hash, so to speak.

This was at best very subtle.

So my question is why is this? Before this little experiment with my CDPlayer, and now possibly my amp,  had always thought that it doesn't matter with AC, because you are connecting with a transformer.

I've heard somewhere that there is suppose to be a test to tell if your AC wiring in to the particular audio device is correct or not.  So if anyone can shed some light on this subject, that would be helpful.

Ray

[miklorsmith]

Liudas from Lessloss sent me the following message on this question to check AC polarity in your house:

Rule #1: Make sure you have a real ground. This means that it doesn't swing with the AC current and it actually does go somewhere. Like deep into the ground. The fatter your home's wires, the better. Marty DeWulf has some good tips on this on his website.
 
Rule #2: Check out this picture (attached). This is how the plug should look when you check for polarity. If the plug is upside down, or sideways, it makes no difference, since there are no rules for this. The positive polarity should be the one which is marked in this picture, meaning that if the ground holes were on top, then the positive polarity would be on the left, and not on the right, as it is here.


 
Rule #3: To test for polarity, you need to buy one of these (see attached picture). It is a screwdriver polarity tester with an LED in it. You can get one at your local electrical hardware store (shouldn't cost but $1 or $2). Tell the guys there that you want to check your 120V wall socket's polarity and they'll get you the right tool for it.


 
Rule #4: What you do is you stick the screwdriver into the holes and where the LED lights up, that's where the phase is. Where it doesn't light up, that's where the phase is NOT. You touch a metal thing on the screwdriver and that's what makes the LED light up (your body acts as ground). Never touch more than one connection simnultaneously!!! Don't have your kids watching when you carry out this test, needless to say. It is a standard electrician's test, but ask about it if you aren't sure about what you're doing. Be safe, please.
 
Rule #5: You can also check if everything is correct by checking on the IEC end of the power cables, too. There are three holes, and the hole marked "L" should be the only one where the LED lights up, when you stick the screwdriver in. Again, you are never to stick in anything into two or more holes simultaneously. Just poke one hole at a time and you will see the LED come on when your finger is on the metal thing on the screwdriver.

[guest1632]

Liudas from Lessloss sent me the following message on this question to check AC polarity in your house:

Rule #1: Make sure you have a real ground. This means that it doesn't swing with the AC current and it actually does go somewhere. Like deep into the ground. The fatter your home's wires, the better. Marty DeWulf has some good tips on this on his website.
 
Rule #2: Check out this picture (attached). This is how the plug should look when you check for polarity. If the plug is upside down, or sideways, it makes no difference, since there are no rules for this. The positive polarity should be the one which is marked in this picture, meaning that if the ground holes were on top, then the positive polarity would be on the left, and not on the right, as it is here.


 
Rule #3: To test for polarity, you need to buy one of these (see attached picture). It is a screwdriver polarity tester with an LED in it. You can get one at your local electrical hardware store (shouldn't cost but $1 or $2). Tell the guys there that you want to check your 120V wall socket's polarity and they'll get you the right tool for it.
 
Rule #4: What you do is you stick the screwdriver into the holes and where the LED lights up, that's where the phase is. Where it doesn't light up, that's where the phase is NOT. You touch a metal thing on the screwdriver and that's what makes the LED light up (your body acts as ground). Never touch more than one connection simnultaneously!!! Don't have your kids watching when you carry out this test, needless to say. It is a standard electrician's test, but ask about it if you aren't sure about what you're doing. Be safe, please.
 
Rule #5: You can also check if everything is correct by checking on the IEC end of the power cables, too. There are three holes, and the hole marked "L" should be the only one where the LED lights up, when you stick the screwdriver in. Again, you are never to stick in anything into two or more holes simultaneously. Just poke one hole at a time and you will see the LED come on when your finger is on the metal thing on the screwdriver.

Hmmm . . . picture not coming through.  How do I get it to show up?

Hi Miklorsmith,

I'll look in to that. Now, since this amp is a DIY build, how do I test it to make sure it is polarity correct?

Ray

[miklorsmith]

No idea.  I KNEW I shouldn't have replied to anything in The Lab.   

[guest1632]

No idea.  I KNEW I shouldn't have replied to anything in The Lab.   

Hey no problem. The info you gave me was great.

Ray

[Occam]

A mickeymouse point about nomenclature. Usually?, in North America, the narrow blade is generally called 'hot', the wider blade 'neutral' and the rounded centered opening '(safety)ground'. I find this chart tremendously helpful, which is why I have it in both my gallery and my computer.


I've got a couple of these outlet testers

Which tell you if your (NA)outlet is wired correctly. Note - It doesn't tell you how good the connections are, simply if they're correct, and if not, generally what is miswired. They're less than $4 at Hechinger.

Some relevant links on minimizing reactive leakage currents to ground -
Bound for Sound Article
http://boundforsound.com/tweak.htm

Jon Risch's comments -
http://www.AudioAsylum.com/audio/tweaks/messages/36909.html

And now for my cautionary comments -

NEVER EVER reverse the wiring of a polarized plug. If you wish to reverse 'hot' and 'neutral' wiring to minimize reactive leakage currents, it must be done internally to the component and that reversal must only be done after the power switch and fuse/breaker so that these still effectively act on the 'hot' line. If you don't understand this, don't even think about doing this. AC voltages can and do kill.

If you've a vintage component that has a polarized 2 prong plug, you MUST do the following test.  Check for continuity from each blade of the plug to the conductive parts of the chassis. Although its be against code for going on 40 years, some (even very good) vintage components connected the neutral to the chassis. If you find such continuity, talk to someone who is knowledgeable and competent in vintage components and don't even think about doing any reversals on your own, you will make your chassis 'live' and possibly kill yourself. (this is why balanced power is problematic on some vintage components)

There is no such thing as a 'cheater' adapter. These adapters are used to provide a grounded receptacle to an outlet that was not grounded by connecting the wire or metal tag to a grounded screw on the outlet box. If you know what you are doing, these adapters are useful for temporary diagnostic purposes ONLY. If you're going to defeat the existing ground do not mention or discuss it on AudioCircle. You are free to endanger your own and your loved ones lives, if you are that foolish,  but not the safety AudioCircle members.

[guest1632]

A mickeymouse point about nomenclature. Usually?, in North America, the narrow blade is generally called 'hot', the wider blade 'neutral' and the rounded centered opening '(safety)ground'. I find this chart tremendously helpful, which is why I have it in both my gallery and my computer.


I've got a couple of these outlet testers

Which tell you if your (NA)outlet is wired correctly. Note - It doesn't tell you how good the connections are, simply if they're correct, and if not, generally what is miswired. They're less than $4 at Hechinger.

Some relevant links on minimizing reactive leakage currents to ground -
Bound for Sound Article
http://boundforsound.com/tweak.htm

Jon Risch's comments -
http://www.AudioAsylum.com/audio/tweaks/messages/36909.html

And now for my cautionary comments -

NEVER EVER reverse the wiring of a polarized plug. If you wish to reverse 'hot' and 'neutral' wiring to minimize reactive leakage currents, it must be done internally to the component and that reversal must only be done after the power switch and fuse/breaker so that these still effectively act on the 'hot' line. If you don't understand this, don't even think about doing this. AC voltages can and do kill.

If you've a vintage component that has a polarized 2 prong plug, you MUST do the following test.  Check for continuity from each blade of the plug to the conductive parts of the chassis. Although its be against code for going on 40 years, some (even very good) vintage components connected the neutral to the chassis. If you find such continuity, talk to someone who is knowledgeable and competent in vintage components and don't even think about doing any reversals on your own, you will make your chassis 'live' and possibly kill yourself. (this is why balanced power is problematic on some vintage components)

There is no such thing as a 'cheater' adapter. These adapters are used to provide a grounded receptacle to an outlet that was not grounded by connecting the wire or metal tag to a grounded screw on the outlet box. If you know what you are doing, these adapters are useful for temporary diagnostic purposes ONLY. If you're going to defeat the existing ground do not mention or discuss it on AudioCircle. You are free to endanger your own and your loved ones lives, if you are that foolish,  but not the safety AudioCircle members.

Hi Occam,

Let me first state that I am in no way telling people to disable the safety ground on any equipment. If you read my earlier posts, I had taken some precaustions on which wire was what. So again, all I want to know is once it is determined if your wall socket is polarized correctly, because my amp is DIY, all I want to know is how to determine if the AC IEC is wired correctly.

Ray

[Occam]

Ray,

Sincere apologies if you or anyone else thought I was questioning the safety of your intended investigations. The later comments were general cautionary ones, appropriate for any discussion of connecting mains lines to components, and not specifically directed towards you.

Regards,
Paul

[guest1632]

Ray,

Sincere apologies if you or anyone else thought I was questioning the safety of your intended investigations. The later comments were general cautionary ones, appropriate for any discussion of connecting mains lines to components, and not specifically directed towards you.

Regards,
Paul

Hey Paul,

No problem, just wanted this to be understood.

So do you have any ideas that could help me here?

Ray

[Occam]

Ray,

The easiest method would be to use a double pole double throw toggle switch wired for phase reversal of the ac situated between the normal on-off switch & fusing, and your transformer primary. Consider  the 6 terminals of this switch. The 'line' and 'neutral' outputs to the transformer primary would come from the center 2 terminals of the switch. 2 insulated wires form an X diagonally across the 'throws' on the opposite ends of the switch. The intput is taken from the two terminals (poles) at one end (throw). When the toggle in one direction it outputs in normal phase, and when its in the opposite direction the connection is made via the 'X' reversing phase. I've included a picture of the wiring of the switch (though I don't know how helpful it is)

I believe this is what Steve Sammet of SAS Audio does on his preamps to provide AC phase reversal.
Alternatively, you could use a center-off dpdt toggle switch for that same purpose, if and only if you fuse both the 'line' and the 'neutral'. This single switch could serve as both the on-off and phase reveral switch. I believe this is what Andyr did on his AKSA poweramp. Its a bit awkward for others to use, as in one direction its on with normal phase, in the center its off, and in the other direction its on but with reversed AC phase. Its just not as intuitively obvious as a normally operating switch.

Hope this helps,
Paul

[guest1632]

Ray,

The easiest method would be to use a double pole double throw toggle switch wired for phase reversal of the ac situated between the normal on-off switch & fusing, and your transformer primary. Consider  the 6 terminals of this switch. The 'line' and 'neutral' outputs to the transformer primary would come from the center 2 terminals of the switch. 2 insulated wires form an X diagonally across the 'throws' on the opposite ends of the switch. The intput is taken from the two terminals (poles) at one end (throw). When the toggle in one direction it outputs in normal phase, and when its in the opposite direction the connection is made via the 'X' reversing phase. I've included a picture of the wiring of the switch (though I don't know how helpful it is)

I believe this is what Steve Sammet of SAS Audio does on his preamps to provide AC phase reversal.
Alternatively, you could use a center-off dpdt toggle switch for that same purpose, if and only if you fuse both the 'line' and the 'neutral'. This single switch could serve as both the on-off and phase reveral switch. I believe this is what Andyr did on his AKSA poweramp. Its a bit awkward for others to use, as in one direction its on with normal phase, in the center its off, and in the other direction its on but with reversed AC phase. Its just not as intuitively obvious as a normally operating switch.

Hope this helps,
Paul

Hmmm, hadn't thought of that. However, this doesn't answer my question. Supposing that my outlet is wired correctly. How do I make sure the premaries are also in polarity with the outlet? What test do I do to check that out?

That switch idea will have to give that one some thought.

Ray

[Occam]

Ray - as you said 'primaries' and your in the States, I'll break this down into a 2 part answer.
1. If you've dual primaries on your transformer to allow it to be wired for either 120 or 240vac operation, and as your SKA? amp is presently running correctly on 120vac, you already have your primaries paralleled properly, 'dot' to 'dot' and 'no-dot' to 'no-dot' as indicated in the wiring diagram of whatever transformer you're using. I assume this really isn't what you're asking.
2. Now the second answer as to which orientation of  'hot' and 'neutral', with one way nominally being the way you have it presently hooked up, and the other being reversed, the answer is either; they'll both work. Now, the answer to the question as to which is preferable is (IMO) the one that give the lowest leakage current to chassis as indicated by the procedures outlined in either of the 2 references I previously provided links to -
http://boundforsound.com/tweak.htm
http://www.audioasylum.com/audio/tweaks/messages/36909.html
These 2 links outline the procedures, and I really don't think I could explain them any more clearly.

[guest1632]

Sorry about that, didn't look at the links.

Ray
Ray - as you said 'primaries' and your in the States, I'll break this down into a 2 part answer.
1. If you've dual primaries on your transformer to allow it to be wired for either 120 or 240vac operation, and as your SKA? amp is presently running correctly on 120vac, you already have your primaries paralleled properly, 'dot' to 'dot' and 'no-dot' to 'no-dot' as indicated in the wiring diagram of whatever transformer you're using. I assume this really isn't what you're asking.
2. Now the second answer as to which orientation of  'hot' and 'neutral', with one way nominally being the way you have it presently hooked up, and the other being reversed, the answer is either; they'll both work. Now, the answer to the question as to which is preferable is (IMO) the one that give the lowest leakage current to chassis as indicated by the procedures outlined in either of the 2 references I previously provided links to -
http://boundforsound.com/tweak.htm
http://www.audioasylum.com/audio/tweaks/messages/36909.html
These 2 links outline the procedures, and I really don't think I could explain them any more clearly.

[guest1632]

Ray - as you said 'primaries' and your in the States, I'll break this down into a 2 part answer.
1. If you've dual primaries on your transformer to allow it to be wired for either 120 or 240vac operation, and as your SKA? amp is presently running correctly on 120vac, you already have your primaries paralleled properly, 'dot' to 'dot' and 'no-dot' to 'no-dot' as indicated in the wiring diagram of whatever transformer you're using. I assume this really isn't what you're asking.
2. Now the second answer as to which orientation of  'hot' and 'neutral', with one way nominally being the way you have it presently hooked up, and the other being reversed, the answer is either; they'll both work. Now, the answer to the question as to which is preferable is (IMO) the one that give the lowest leakage current to chassis as indicated by the procedures outlined in either of the 2 references I previously provided links to -
http://boundforsound.com/tweak.htm
http://www.audioasylum.com/audio/tweaks/messages/36909.html
These 2 links outline the procedures, and I really don't think I could explain them any more clearly.

Hi Paul,

Actually, you can. Assuming for the moment, the wall outlets are set correctly, ... The first article doesn't state what you do with the black plug. Red and Black. Red goes to the chassis. Now, a possible problem here, the RCA's are floating. So on the 2nd article one goes to the outside of the RCA, and the other goes to the "safety ground" connection.  Like you said, a double pole, double throw switch might just be the ticket. I do have this cord made up, so with a few twists, I can change polarity as it were on the cord. in keeping with your caughtious approach, the safety ground has not been lifted. I might have to go back and ask Greg for further instructions here. But if you have some further ideas, I'm open to them. Sorry to ask you to be a bit more granular.

Ray 

[Occam]

Ray - In connecting the meter, if red goes to the chassis, black goes to an outlet's functioning safety ground.