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Emotiva pt1 phase issues rd 02a.

wadimek11

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Salesman tried selling me expensive cables. He connected some streamer to emotiva pt1 then basx 300. He then rotated cable and sound was way different. I have hard time figuring out what happend. Of course he said that the reason why I don't like those speakers is because all my installation in the house might be in wrong phase and that I don't know anything. Can anyone explain how is this possible and what could have caused the issue with the rotating rd 02a cable in emotiva pt1 unit?
 
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wadimek11

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What was hearable was complete balance change which was weird because I naver heard anything like that before and I never was able to replicate it at home.
 

MaxwellsEq

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Obviously having both speakers in phase is essential (I'm assuming it's wired correctly).
Swapping the absolute phase may change the sound. This is where on both speakers you put the black plug into the red socket and vice versa. For pure tones there's no impact, but for some asymmetric signals there may be a difference.
 
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wadimek11

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What I meant is that both speakers from amp were in phase. He just switched the power phase and amp changed sound drastically. Why is that? Shouldn't transformer cancel any phase issue in the power?
 

MaxwellsEq

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He just switched the power phase and amp changed sound drastically. Why is that? Shouldn't transformer cancel any phase issue in the power?
Interesting! I'd be quite surprised if swapping the mains phase makes a measurable difference. However, electronic power supplies are not like bulbs where phase is totally irrelevant.
 

RayDunzl

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He just switched the power phase and amp changed sound drastically.

The AC feed to your house (in the US) has three wires.

120vAC referenced to ground

120VAC referenced to ground with polarity opposite to the other feed - 180 degree phase difference.

0V Ground Return

The out of phase 120VAC provides 240VAC when the load is across the two phases, for kitchen range/oven/clthes dryer, Central Air conditioner, and any other high power applications.

At the breaker box, half the breakers will wire to one 120VAC line, and half to the other.

Your gear shouldn't care which "phase" it is connected to. They are the same, unless compared to each other, like a mirror image.


Why is that?

Why it "sounded different" would be a mystery, shouldn't be related to which 120VAC wire from the transformer outside feeds the gear.

Shouldn't transformer cancel any phase issue in the power?

The gear transformer only sees 120VAC 60Hz on either feed.

I would go "Uh huh" and move on.

Salesman tried selling me expensive cables.

Uh huh.

---

There might be an issue if some of the gear is on one breaker (and phase) and some on the another. Maybe . Ground noise? Maybe. Probably not.

Or he has something interesting about his power at the store.


He then rotated cable and sound was way different.

Different how?
 
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wadimek11

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I honestly have no idea what happened. Thats why Im asking on forum. I have no idea why it changed sound but it was really hearable and difference was quite drastic. I wonder if he could switched something else from back of the device that made such a difference. Whole changed took 10seconds and he showed the cable really clearly although I looked from the front of the device. It just doesn't let me sleep about what exactly happened there.
 
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wadimek11

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It was in Europe on 240V 50hz power outlet.
The AC feed to your house (in the US) has three wires.

120vAC referenced to ground

120VAC referenced to ground with polarity opposite to the other feed - 180 degree phase difference.

0V Ground Return

The out of phase 120VAC provides 240VAC when the load is across the two phases, for kitchen range/oven/clthes dryer, Central Air conditioner, and any other high power applications.

At the breaker box, half the breakers will wire to one 120VAC line, and half to the other.

Your gear shouldn't care which "phase" it is connected to. They are the same, unless compared to each other, like a mirror image.




Why it "sounded different" would be a mystery, shouldn't be related to which 120VAC wire from the transformer outside feeds the gear.



The gear transformer only sees 120VAC 60Hz on either feed.

I would go "Uh huh" and move on.



Uh huh.

---

There might be an issue if some of the gear is on one breaker (and phase) and some on the another. Maybe . Ground noise? Maybe. Probably not.

Or he has something interesting about his power at the store.




Different how?
 

Rusty

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I'm thinking what you are describing is reversing a non-polarized plug in the socket? If so, older vintage gear used to have such plugs (not just without a ground pin, but also identical sized blades for hot/neutral that would allow turning the plug either way), and I have turned the plug and heard differences, primarily with preamplifiers and tuners. Don't know why, but I've heard it.
 

AdamG

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First guess. He turned the volume up when you were not looking.

Second guess. He did nothing, but “expectation bias” kicked in and presto magico you heard a difference.

That’s all I got! :eek:
 
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wadimek11

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First guess. He turned the volume up when you were not looking.

Second guess. He did nothing, but “expectation bias” kicked in and presto magico you heard a difference.

That’s all I got! :eek:
There is no way. It killed highs completely. I know what is small difference and what feels like someone would -9db high tones.
 
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wadimek11

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I think thats exactly what happend. Although I don't know why it even made a difference. I couldn't replicate it at home with any of my devices.
I'm thinking what you are describing is reversing a non-polarized plug in the socket? If so, older vintage gear used to have such plugs (not just without a ground pin, but also identical sized blades for hot/neutral that would allow turning the plug either way), and I have turned the plug and heard differences, primarily with preamplifiers and tuners. Don't know why, but I've heard it.
 

MaxwellsEq

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There is no way. It killed highs completely. I know what is small difference and what feels like someone would -9db high tones.
There's definitely something wrong, then. Between the mains pins and the device output there are: (linear) a transformer, rectifiers, capacitors. For lower voltage/power devices there is then a regulator (or more). Then, each gain stage will typically have supply noise-rejection capability. Finally feedback will correct errors.

Whilst I can potentially believe that the transformer/rectifiers may be designed in such a way that it's imperative to keep the live side connected to the live pin, none of the other components should be affected. Certainly, I can't see how the frequency response would be affected as significantly as you describe.

The only way forward is to demonstrate this on the bench and then identify why. There is no magic in electronics.
 
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