Is Your System's Noise Floor Low Enough? - Page 5 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #41 of 59 Old 12-18-15, 09:35 AM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

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If you can turn the amp up and down without an increase in noise volume then the point of the noise is before the amp.
Don't you mean after the amp?


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post #42 of 59 Old 12-18-15, 10:25 AM
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Re: Is Your System's Noise Floor Low Enough?

Good question Craver, but I was thinking that the amp is the last item in the chain before the speakers, and, I was considering a pro amp which has volume controls. With everything in the system off except the amp, listen and if it is quiet, then the problem most probably comes from something before the amplifier.

Does that make sense or did I still get it wrong ??

Good Listening

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post #43 of 59 Old 12-19-15, 06:20 PM
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Re: Is Your System's Noise Floor Low Enough?

Hi jack, I follow you. I can only speak for my personal situation. What I find odd is that by changing volume on the avr OR the amp, the sound stays the same. I won't be able to dig into it for awhile but when i do, I'm going to be very thorough, as tending to the snake pit has been on my list for awhile.


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post #44 of 59 Old 12-20-15, 11:17 AM
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Re: Is Your System's Noise Floor Low Enough?

I spent the afternoon in NYC yesterday, went to LUPA for lunch then headed over to Stereo Exchange to a listening session with Sandy Gross from Golden Ear...this after giving blood to Red Cross in the morning, needless to say I was tired when I got home last night.

This morning I decided to listen to my noise floor...
I DID hear hiss with nothing playing (at MAX V within 1") so on advice from this thread, I removed my Tripplite UPS and noticed all the hiss (at MAX V within 1") had moved out...

Guess what, I did hear a very faint 60 cycle hum AFTER the hiss was removed...(which I DID NOT hear with the hiss) I grounded my Monster power to my Tripplite NON-UPS 1800AC line conditioner to the Green ground in the outlet and now THAT is eliminated.

Thank you all for your contributions to great little tweak I would have never ventured if I didn't read it here!
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post #45 of 59 Old 12-22-15, 08:40 PM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

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Savjac wrote: View Post
With everything in the system off except the amp, listen and if it is quiet, then the problem most probably comes from something before the amplifier.

Does that make sense or did I still get it wrong ??
That makes sense.

With the entire system running, if the noise level goes up and down with the volume control, the noise is entering the system before the volume control. It could be getting in
  • with the signal on an input
  • via the power or grounding and entering the AVR's circuitry before the volume control
  • via magic (not really, just seeing if you're listening)


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post #46 of 59 Old 12-22-15, 08:44 PM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

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albe wrote: View Post
I spent the afternoon in NYC yesterday, went to LUPA for lunch then headed over to Stereo Exchange to a listening session with Sandy Gross from Golden Ear...this after giving blood to Red Cross in the morning, needless to say I was tired when I got home last night.

This morning I decided to listen to my noise floor...
I DID hear hiss with nothing playing (at MAX V within 1") so on advice from this thread, I removed my Tripplite UPS and noticed all the hiss (at MAX V within 1") had moved out...

Guess what, I did hear a very faint 60 cycle hum AFTER the hiss was removed...(which I DID NOT hear with the hiss) I grounded my Monster power to my Tripplite NON-UPS 1800AC line conditioner to the Green ground in the outlet and now THAT is eliminated.

Thank you all for your contributions to great little tweak I would have never ventured if I didn't read it here!
I am more than a little embarrassed how long I have put up with noises and buzzes like that. Way to go getting it fixed!


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post #47 of 59 Old 12-22-15, 09:07 PM
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Re: Is Your System's Noise Floor Low Enough?

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AudiocRaver wrote: View Post
That makes sense.

With the entire system running, if the noise level goes up and down with the volume control, the noise is entering the system before the volume control. It could be getting in
  • with the signal on an input
  • via the power or grounding and entering the AVR's circuitry before the volume control
  • via magic (not really, just seeing if you're listening)
Yes Mr. AC I am listening, but I think you may not be all that far off base. I am not an engineer nor did i take any electrical class back in school so electricity, electronics and computers are indeed magic to me. I am the hands on guy so I understand mechanical but those other things provide me with no clues. Your chart early on gave me nightmares LOLOL

Good Listening

Jack

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post #48 of 59 Old 12-23-15, 07:47 AM
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Quote:
Savjac wrote: View Post
If anyone wants to try an experiment this one is cool. Much of the equipment we use does not have a ground plug but merely a double bump on one of the prongs of our power cable. A manufacturer once told me at an audio show in Chicago that when these electronics are manufactured, there is only a 50/50 chance that the line assemblers will get the negative portion of the power cord soldered to the right pin in the electronics. He went on to tell me how to check. You put a cheater plug ( And yes this works with 3 pronged plugs as well ) on the original make end of the chord and plug it into the wall. Then take your multi meter and set it low and take one end of the meter cable and touch the ground of the wall socket and the other end of the meter cable touch a metal component of your equipment. Write down the value. Now turn off the equipment and change the orientation of your cheater plug in the wall outlet and do the same thing with your multi meter and write down the values. Which ever of the 2 values that is lowest would indicate which way the negative side of the power cord should reside in the wall outlet.
By the way, It works.
I really don't understand how that would work with a 2 prong plug?!? A 3 prong I could see being miswired (I've seen it plenty in clients' homes) but A/C is delivering 60v on each leg every 1/60 of a second (120V@60Hz). That means half the time your negative poll is switched. This works because virtually all electronics use DC power internally. So inside your component there is an AC to DC converter. This is usually two parts a transformer is used to step down the voltage:
https://en.m.wikipedia.org/wiki/Transformer
And an AC/DC converter:
https://en.m.wikipedia.org/wiki/Rectifier
So regardless of what leg is plugged into what leg of a 2 prong it should be the same.
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post #49 of 59 Old 12-23-15, 09:11 AM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

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rab-byte wrote: View Post
I really don't understand how that would work with a 2 prong plug?!? A 3 prong I could see being miswired (I've seen it plenty in clients' homes) but A/C is delivering 60v on each leg every 1/60 of a second (120V@60Hz). That means half the time your negative poll is switched. This works because virtually all electronics use DC power internally. So inside your component there is an AC to DC converter. This is usually two parts a transformer is used to step down the voltage:
https://en.m.wikipedia.org/wiki/Transformer
And an AC/DC converter:
https://en.m.wikipedia.org/wiki/Rectifier
So regardless of what leg is plugged into what leg of a 2 prong it should be the same.
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.


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post #50 of 59 Old 12-23-15, 09:53 AM
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So a two prong is only getting voltage half the time?!?
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