Why does ac polarity affect sound quality?

[bob_m_54]

5 hours ago, andyr said:

 @jeromelang ... can I suggest that you should change the subject title again ... to avoid mis-directing people into thinking you are advocating unsafe electrical practices?

 

How about "Why does ac orientation affect sound quality "?

 

BTW - I use the 'AC meter method' when determining which end of the power transformer's primary winding should be connected to Active.  As you say, measuring for the lower AC reading on the chassis gives the 'right way round'.

 

Andy

 

Are you talking about class 1 (3 pin plug), or class 2 (2 pin plug) equipment here?

 

Class 1 equipment will have a chassis connected to ground. So if you get a reading of more than a few mV between the chassis, and the wall socket Earth contact, then you have a safety ground problem, and shouldn't be using the equipment.

If you are talking about a Class 2 piece of equipment (double insulated), then the outer metal case will be floating wrt the wall socket Earth contact, so any measurement between the outer case and the Earth contact is meaningless, unless you apply a load across those two points (eg a 10K ohm resistor). It's basically the same as touching one probe to the wall Earth contact, and holding the other probe above your head.

 

Edit: I actually cleaned that up a bit. When doing stray voltage checks on military aircraft, after modifications in the weapons systems (no you don't want stray volts) One of the tests involves connecting a 10K resistor between the measured point and aircraft ground (yes a weird name for it), and measuring the voltage on a floating signal line. The maximum voltage was something like 5mV DC, or 50mV, I can't really remember. One of the guys doing the test measured the voltage and got 5VDC, which is quite a bit higher, and was ready to sign off on it. I went WTF?

 

His reply was we always get that, so no big deal... Holy Crap Batman.... I looked at what he was doing and asked why he didn't have the 10K load resistor across the measured points. His reply was .. we don't have one...

 

I tried to explain to him why his measurements were meaningless without the load resistor, and what I actually said was .. "you may as well stick the other probe up yer bum and measure it" he didn't see the funny side of it..

 

You have to remember this was on a wire that could potentially deliver a nice big fat explosive device at entirely an inappropriate time..

 

Yes they are out there...

Edited May 23, 2020 by bob_m_54

[Steffen]

19 hours ago, Addicted to music said:

So those who think they can detect a difference which side the active is connected to a transformer; please explain!

 

From memory, I think it concerned double-insulated equipment, connected via only two mains pins. You could tell which way the mains plug was in from the slight tingle you got (or didn’t get) when touching the metal case. I think this is due to capacitative coupling of the mains winding to the transformer core. Nothing to worry about normally, and not a safety issue, but...

 

If two connected pieces of stereo gear were plugged into the mains in opposing ways then there could be a significant potential between their RCA ground contacts, for example. That’s why it was important to get them all plugged into mains the same way.

 

This would not be an issue of course where the equipment was earthed via a three-pin mains lead.

Edited May 24, 2020 by Steffen
correction

[bob_m_54]

5 hours ago, Steffen said:

From memory, I think it concerned double-insulated equipment, connected via only two mains pins. You could tell which way the mains plug was in from the slight tingle you got (or didn’t get) when touching the metal case. I think this is due to capacitative coupling of the mains winding to the transformer core. Nothing to worry about normally, and not a safety issue, but...

 

If two connected pieces of stereo gear were plugged into the mains in opposing ways then there could be a significant potential between their RCA ground contacts, for example. That’s why it was important to get them all plugged into mains the same way.

 

This would not be an issue of course where the equipment was earthed via a three-pin mains lead.

I can't see that happening, to be honest. It is only a floating voltage with no measurable current available, unless of course there is an insulation breakdown fault through both insulation methods.

[aussievintage]

31 minutes ago, bob_m_54 said:

I can't see that happening, to be honest. It is only a floating voltage with no measurable current available, unless of course there is an insulation breakdown fault through both insulation methods.

It's crazy to measure floating voltages.  I remember as students, measuring the voltage on our hands when standing in a high rise building with fluoro lighting overhead etc.  Yeah, we had measured over a hundred volts on us.

[sir sanders zingmore]

Back the the OPs question… he was asking about people's experience (assuming they lived to tell the tale).

I posted my experience (zero difference), anyone else tried it?

Edited May 24, 2020 by sir sanders zingmore

[andyr]

1 hour ago, sir sanders zingmore said:

Back the the OPs question… he was asking about people's experience (assuming they lived to tell the tale).

I posted my experience (zero difference), anyone else tried it?

 

Well, in Oz - and the UK - it's difficult to swap around how the mains transformer is connected to Active and Neutral, in commercially bought gear.  So I doubt many people have actually experienced the difference in sound. 

 

But it's easy to do this with DIY gear.  I've never compared the sound of an amp either way round but - after reading an article on this subject in "Bound for Sound" - with every amp I've built in the last 20 years, as a matter of course I test to see which orientation of the primary winding gives the lowest AC leakage voltage on the chassis.

Note: there is a temporary 'trick' when doing this - which I am loath to expose on a public post, as I expect it would result in my post being deleted. 

 

Andy

 

Edited May 24, 2020 by andyr

[pwstereo]

15 hours ago, andyr said:

...test to see which orientation of the primary winding gives the lowest AC leakage voltage on the chassis.

Note: there is a temporary 'trick' when doing this - which I am loath to expose on a public post, as I expect it would result in my post being deleted.

I'm picturing you using your tongue, like the 9V battery test

[andyr]

1 minute ago, pwstereo said:

I'm picturing you using your tongue, like the 9V battery test

 

C'mon, Peter - that's the sort of comment one makes about Sand Gropers ... not a fellow Victorian. 

 

Andy

 

[MTsoul]

On 24/05/2020 at 12:28 PM, Steffen said:

If two connected pieces of stereo gear were plugged into the mains in opposing ways then there could be a significant potential between their RCA ground contacts, for example. That’s why it was important to get them all plugged into mains the same way.

I'm somehow experiencing this and I'm hoping you more electrically educated SNAers can help me. 

 

Yamaha R-N602 with 3 pin and stax 727 with 3 pin. Both plugged into 3 pin power boards. When I connect the two via rca, the Yamaha says speaker short circuit, and when I hold the RCAs and touch the chassis, I can feel the vibration of the current. Not sure what I can do. 

[stereo coffee]

40 minutes ago, MTsoul said:

I'm somehow experiencing this and I'm hoping you more electrically educated SNAers can help me. 

 

Yamaha R-N602 with 3 pin and stax 727 with 3 pin. Both plugged into 3 pin power boards. When I connect the two via rca, the Yamaha says speaker short circuit, and when I hold the RCAs and touch the chassis, I can feel the vibration of the current. Not sure what I can do. 

Firstly don't assess by touching , as there is risk of electric shock, which can be FATAL  Turn the equipment OFF, and disconnect from the power point  NOW , and await until fixed by a licensed electrician. 

https://sound-au.com/articles/mains-safety.htm

 

High on the list of Why is or could be a extension lead wired wrongly, see the article. 

 

You need a licensed electrician to inspect , assess and make your power lead and possibly other equipment awaiting diagnoses, equipment safe . 

https://www.elextrofix.com.au/?keyword=Electrician Near Me&matchtype=p&device=c&msclkid=9d876a095a991f45101e34c2cd10bdba

Edited May 25, 2020 by stereo coffee

[bob_m_54]

2 hours ago, MTsoul said:

I'm somehow experiencing this and I'm hoping you more electrically educated SNAers can help me. 

 

Yamaha R-N602 with 3 pin and stax 727 with 3 pin. Both plugged into 3 pin power boards. When I connect the two via rca, the Yamaha says speaker short circuit, and when I hold the RCAs and touch the chassis, I can feel the vibration of the current. Not sure what I can do. 

Is the power board a commercially made device? It sounds like you have a serious problem with either the power board wiring, the equipment power plug wiring, or even the wall socket wiring.

Edited May 25, 2020 by bob_m_54

[jeromelang]

5 hours ago, MTsoul said:

I'm somehow experiencing this and I'm hoping you more electrically educated SNAers can help me. 

 

Yamaha R-N602 with 3 pin and stax 727 with 3 pin. Both plugged into 3 pin power boards. When I connect the two via rca, the Yamaha says speaker short circuit, and when I hold the RCAs and touch the chassis, I can feel the vibration of the current. Not sure what I can do. 

This unit, sold in Australia might come with a 3-pin aussie ac plug, but it is anything but grounded. Just look at the thin, captive powercord. There's only 2 conductor wires running within the thin dielectric outer jacket.

 

 

 

Edited May 25, 2020 by jeromelang

[Batty]

It looks as though that cord has been replaced, there is space for a 3 core cable.

[Steffen]

6 hours ago, jeromelang said:

This unit, sold in Australia might come with a 3-pin aussie ac plug, but it is anything but grounded. Just look at the thin, captive powercord. There's only 2 conductor wires running within the thin dielectric outer jacket.

 

 

 

Indeed. If there is a 3-pin plug at the end of that 2-conductor cord, then it’s most likely a home jobbie, and the source of the issues described.

 

Edited May 25, 2020 by Steffen

[pete_mac]

That Yamaha has the ‘double box’ symbol on the rear label. It is double insulated and thus is manufactured without an earth wire. 

Edited May 25, 2020 by pete_mac

[Lochawe]

22 hours ago, andyr said:

C'mon, Peter - that's the sort of comment one makes about Sand Gropers ... not a fellow Victorian. 

Sandgropers?

Haven't heard that word for decades...

Should I be offended : )

[MTsoul]

1 hour ago, pete_mac said:

That Yamaha has the ‘double box’ symbol on the rear label. It is double insulated and thus is manufactured without an earth wire. 

Thanks, I was just checking that in the manual. 

 

The RCAs are still buzzing though. Any ideas on that? Possibly from the network connection or the turntable? 

 

My layman's guess would be different circuits for the yam and the stax  creating a ground loop? But I only understand half of the sentence I just wrote. 

2 hours ago, Batty said:

It looks as though that cord has been replaced, there is space for a 3 core cable.

Nothing has been replaced, that's straight from the manufacturer

 

2 hours ago, Steffen said:

If there is a 3-pin plug at the end of that 2-conductor cord, then it’s most likely a home jobbie,

No Sir! Wouldn't dream of doing that. 

Edited May 25, 2020 by MTsoul
Extra info

[jeromelang]

Does the R-N602 come with a factory molded ac plug or does it look like an adaptor encased over another plug? Show a photo?

[MTsoul]

19 minutes ago, jeromelang said:

Does the R-N602 come with a factory molded ac plug or does it look like an adaptor encased over another plug? Show a photo?

Standard 2 pin plug. Sorry for misleading everyone earlier, I was looking at the plug next to it in the powerboard. 

 

So Im thinking I need to run a ground between the stax and the yam and see if that fixes it. 

[jeromelang]

16 minutes ago, MTsoul said:

Standard 2 pin plug. Sorry for misleading everyone earlier, I was looking at the plug next to it in the powerboard. 

 

So Im thinking I need to run a ground between the stax and the yam and see if that fixes it. 

 

I believe the 602 was "reworked" by their service staff to remove the entire original ac powercord and replace it with one fitted with an aussie ac plug. The reason for reworking is mostly due to sales qty. For Japanese brands, there is usually a minimum qty required by their factory to justify creating a version (mostly adapted from an UK or EU version) just for the australian/nz market. 

 

There should be no doubts their service staff (or maybe service contractors) are diligent enough to ensure the correct safety standards are adhered to (live and neutral orientation properly observed). But, still it could be prudent to check. Because as mentioned before, the wrong ac polarity will result in higher chassis current leakage.

 

The other issue is finding what may introduce extraneous chassis leakage current onto the 602. Besides the stax, what else are connected to the 602? If all are removed, then does the 602 still exhibit chassis leakage? Can you find out one by one which component/cabling is the culprit?

 

There is no need to employ another wire between the stax and the 602. You just need to ground the 602 alone. I have previously posted a simple method to ground Yamaha products with just a mono RCA cable with one end's ground shield wire connected to the earth pin of a 3-pin plug. Done correctly it can even improve sound quality. Search the archive.

 

Remember to remove both the live and neutral pins. An "empty" ac plug with both live and neutral pins still on the plug will cause sonic problems. 

 

The correct directionality of the rca wire to be used for grounding should be determined first before reworking on it, as it will affect sound quality very drastically. 

[jeromelang]

Looks like for the 602, chassis leakage is a common issue. If it bothers you, trying sending it in for checks?

 

 

Edited May 26, 2020 by jeromelang

[MTsoul]

@jeromelang

 

You nailed it. With everything disconnected still feel the chassis leakage on the front panel of the R-N602. Will be looking up your mono rca solution and applying it. 

[jeromelang]

managed to dig out opened top image of R-N602 from a Melbourne retailor

 

Edited May 26, 2020 by jeromelang

[jeromelang]

Zoomed in image. I hate to see the sight of ferrite cores!

 

Edited May 26, 2020 by jeromelang

[davewantsmoore]

8 hours ago, MTsoul said:

My layman's guess would be different circuits for the yam and the stax

If they are both not plugged into the same powerpoint/powerboard ..... then do that.