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post #51 of 60 Old 12-23-15, 10:50 AM
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Re: Is Your System's Noise Floor Low Enough?

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Not quite true. With a 120V two-prong outlet, one prong goes to neutral, which ends up tied to ground back at your service panel or somewhere back there (Talley, help!). The other prong, "hot," goes to 120V. If there is a third prong, the ground, it goes directly to ground at your service panel for safety.

After passing through the power transformer of a typical piece of audio gear with a linear power supply, the rectified and filtered result is DC, as you say. The transformer secondary may or may not be balanced, depending on the design of that piece of gear. On the 120V primary of a power transformer, one lead will go to ground and the other to "hot," as discussed. The incoming AC, at the socket, is not balanced at a 120V outlet, as you suggested. At a 120V outlet, where only one phase of the incoming 240V power is wired, the power will appear unbalanced relative to ground. The 240V power coming into your home is balanced, but you only see both phases of that power in one outlet at a 240V dryer or stove or air conditioner outlet.

With a piece of gear that has a two-prong plug, depending exactly how it is wired inside, the test Savjac described should work.

Some enthusiasts defy all of these rules with special balanced transformers and power distribution, but this is in defiance of code and is rare.
Let me say what I know. your 120V will have one lead hot, one lead neutral and one ground.... even though your neutral is grounded (done at the panel in homes) it is not considered a ground. grounded conductor = neutral, grounding conductor = ground. Also your 240V power at your house is not balanced. The phases are 120 degrees apart. Balanced = 180degrees out of phase from each leg and you get that by grounding the center tap on the secondary. This provides 60V on one side and 60V on other side.

balanced is not a defiance of code but yes it is rare. A requirement for moving to balanced is the need for GFCI protection to remain "in code".

Some equipment like many receivers and bluray players will only use two prong outlets because they are considered to be double insulated and they float the ground. Double insulated appliances are legal and I believe some are done in the audio world to minimize ground loops and the problem exists when you have a pre-amp that is two prong and an amp that is three prong and using RCA connectors because the negative is bonded at some point to the ground in the pre-amp thus causing a ground loop. Balanced connectors helps this but simply grounding all the equipment to a common ground also does this as well.

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post #52 of 60 Old 12-23-15, 06:57 PM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

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Let me say what I know. your 120V will have one lead hot, one lead neutral and one ground.... even though your neutral is grounded (done at the panel in homes) it is not considered a ground. grounded conductor = neutral, grounding conductor = ground. Also your 240V power at your house is not balanced. The phases are 120 degrees apart. Balanced = 180degrees out of phase from each leg and you get that by grounding the center tap on the secondary. This provides 60V on one side and 60V on other side.

balanced is not a defiance of code but yes it is rare. A requirement for moving to balanced is the need for GFCI protection to remain "in code".

Some equipment like many receivers and bluray players will only use two prong outlets because they are considered to be double insulated and they float the ground. Double insulated appliances are legal and I believe some are done in the audio world to minimize ground loops and the problem exists when you have a pre-amp that is two prong and an amp that is three prong and using RCA connectors because the negative is bonded at some point to the ground in the pre-amp thus causing a ground loop. Balanced connectors helps this but simply grounding all the equipment to a common ground also does this as well.
Excellent summary, thanks, Talley. I had completely forgotten about the 120° phase angle on the two 120V phases.

Question: If measuring between those two phases, wouldn't you measure something like 180V between them, a value greater than 120V but less than 240V ??


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post #53 of 60 Old 12-23-15, 07:21 PM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

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So a two prong is only getting voltage half the time?!?
A two prong is getting AC voltage all the time, but it is all on the "hot" lead relative to ground. That voltage is a sine wave, 120V RMS. Each peak gets to 170V peak in each direction relative to ground. In a piece of audio gear with a typical center-tap-secondary and full-wave rectifier power supply, each side of the DC is getting recharged 120 times per second.


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post #54 of 60 Old 12-23-15, 08:35 PM
 
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Re: Is Your System's Noise Floor Low Enough?

Is the 3rd wire different once it exits the house... I ask this because last year we had over 200V going to all our outlets in the house. PG&E came out to our house, and found that one of the wires (from the transformer on the pole) had a bad connection, and they said the 3rd wire was what controlled the voltage. They said that since the wire had a bad connection it allowed full voltage to go to our house. We lost some thermostats, and a low voltage transformer in the deal.

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post #55 of 60 Old 12-23-15, 09:12 PM
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Re: Is Your System's Noise Floor Low Enough?

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Excellent summary, thanks, Talley. I had completely forgotten about the 120° phase angle on the two 120V phases.

Question: If measuring between those two phases, wouldn't you measure something like 180V between them, a value greater than 120V but less than 240V ??
I can't remember off the top of my head but it's 120v RMS... peak to peak is around 150v. Remember it cycles at 60hz meaning 60 times a second there is ZERO voltage... If you were lightning quick you could touch it and not get shocked but chances are 100.1% your not so your gonna get zapped lol.

All sorts of systems out there... delta high leg, delta corner ground is one that I still don't understand and is dangerous and yes I have encountered it although it's seldom used. wye connected (star) so many variables exist.

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post #56 of 60 Old 12-23-15, 10:13 PM
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Re: Is Your System's Noise Floor Low Enough?

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Is the 3rd wire different once it exits the house... I ask this because last year we had over 200V going to all our outlets in the house. PG&E came out to our house, and found that one of the wires (from the transformer on the pole) had a bad connection, and they said the 3rd wire was what controlled the voltage. They said that since the wire had a bad connection it allowed full voltage to go to our house. We lost some thermostats, and a low voltage transformer in the deal.

sounds funny and really not sure. could of been a number of things. losing a neutral or having a bad connection can fluctuate voltage but man it really depends... alot of utilities will operate different voltages albeit within 5% of eachother. I still find it crazy that you'll have 6-10 powerhouses spread across an entire state and they all work together because they are phase aligned to provide the overall power sharing.

I have to retract my previous statement. Single phase in a home the 240V is a balanced IF derived from a single phase 7200v leg on a 13kv 3phase system. If two transformers are used in deriving 240v from a 13kv system then you'll have 240v that is 120 degrees out of phase. It can depend on where your at (city or urban). TYPICALLY your balanced 240V single phase. Had a discussion with a fellow friend who reminded me that. I haven't been in the residential sector in over 10 years and deal strictly w/ 3 phase now but you can still find residential from 3 phase in more urban areas.. or if your underground too you can 3 phase. Just really all depends on your area.

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post #57 of 60 Old 07-20-16, 09:17 AM
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Re: Is Your System's Noise Floor Low Enough?

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Wow... I've only listened to a few tracks but like you said the clarity but more so the openness has really improved dramatically. (...) but the sound is more centered. It's a very weird change. The instruments show more pinpoint location and have appeared to of moved in slightly but the space or the sound of the room they recorded in has really opened up and grew around my room.

It's definately a change for the plus but wow(...).
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(...) It makes you wonder how systems there are out there that could sound a whole lot better with just a little diagnostic work and a few minor changes.

It is a weird change. Kind of hard to describe the difference until you have heard it. Openness, depth of the darkness between sound images, contrast, the sound that is there seems to stand out more ..
All those comments are thrue.

I got the same impression since yesterday when I finally get rid of a hum that I did even not know that it was there before I cranked up the main volume with the bd player in multi-channel mode and put it to pause. My set-top box is connected via hdmi to the player not the receiver. The only link to the receiver is hdmi cable from the player and hdmi to the TV. Disconnecting the coax cable from the set-top box made the hum to disappear. I first discovered that the cable was not properly grounded outside the house. After having corrected this, the hum was still there! Finally I changed the hdmi cable between the set-top box (cable decoder) and the player. The hum at 60hz was lowered by more than 90%. I also connected a coax cable between the set-top box and the receiver = hum killed and what a difference in the sound and SS&I !

I must to say that I was confused by the fact that the hum was there only in Multi-channel LPCM and not when the sound track is bit streamed. A member of another forum explained to me that there is a difference in the sensibilty to grounds between those 2 modes in the electronics into a gear(!)

Yesterday I thought that it also improved the quality of the SS&I when I listenned music played back by the BD-player and send into the receiver via the analogue RCA cable outputs. I thought that I was imaginating things. But, If I am not mistaken, cd music signal is in PCM then "translated" in electic signal into the player and then send to the rca outputs. Maybe this explains that. :

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post #58 of 60 Old 07-23-16, 03:23 AM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

You have made some real progress. Once you hear the difference, it is unmistakable.


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post #59 of 60 Old 07-25-16, 07:32 AM
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Re: Is Your System's Noise Floor Low Enough?

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(...) it is unmistakable.
That's it. I am most surprise.
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post #60 of 60 Old 02-24-17, 02:10 PM
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Re: Is Your System's Noise Floor Low Enough?

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THE LESSON:

Check your noise floor! With no music running, and with streaming taking place, CAREFULLY crank up your volume level and see what you can hear at the LP and next to your tweeter.

CAUTION - CAUTION - CAUTION - CAUTION - CAUTION - CAUTION - CAUTION - CAUTION - CAUTION
Turn your volume setting down to normal or below before selecting a different source or making ANY change to your AVR settings or anywhere else in your system. Then turn it back up after that change has been made to hear the result.
CAUTION - CAUTION - CAUTION - CAUTION - CAUTION - CAUTION - CAUTION - CAUTION - CAUTION
  • If you hear noise at the LP with a normal listening level, your soundstage is seriously compromised.
  • If you hear noise at the LP with volume at max, or at the tweeter with a normal volume setting, your soundstage is probably somewhat compromised.
  • If you hear noise at the tweeter with volume at max, your soundstage might be somewhat compromised.
Re-awakening a recent thread for a late check-in:
Fascinating, and Kudos to you, sir!
Just when others think your system's max performance has been reached, you wring out another ounce. Reading through this topic reminded me to pay attention to both ambient and system noise floors. Thank you!

.
I try to be as good as my dog thinks I am
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