Is Your System's Noise Floor Low Enough? - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 59 Old 12-16-15, 05:42 PM Thread Starter
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Thanks Wayne. I figured you would say that! I just did a little impromptu check at lunch. The distance is more like 6 inches. The sound is a mix of hiss/hum. The sound doesn't change output no matter how loud or soft the volume. That makes me think 60hz hum. I have 4 dedicated 20a circuits to the wall for the purpose of powering my gear, but everything is plugged into an APC h10. Any ideas? So far, I'm loving this amp.

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Interesting that the noise level does not change with your volume setting. Do you have an external power amp? The noise appears to be entering the system after the volume control of your Yamaha You can try a ground lifter plug on it also to see if that helps. I agree with Tally to try it without the ups also. I had to try a couple to end up with a very quiet model that puts out a pure sine wave when it fires up. And is very quiet. When it comes to hum and noise, the solution can seem mysterious and nonsensical sometimes.


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post #22 of 59 Old 12-16-15, 06:01 PM
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Re: Is Your System's Noise Floor Low Enough?

Yes Wayne. It is an external amp. It's fed by an onkyo txnr-808. The amp is a pro model p2500s. I tried going straight to the wall and it didn't change a thing. Also, nothing changes by altering the gain(or should I say attenuation) knobs on the amp. I used 1/4" to TS connectors. I wonder if it's there?


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post #23 of 59 Old 12-16-15, 10:13 PM
 
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Re: Is Your System's Noise Floor Low Enough?

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Yes Wayne. It is an external amp. It's fed by an onkyo txnr-808. The amp is a pro model p2500s. I tried going straight to the wall and it didn't change a thing. Also, nothing changes by altering the gain(or should I say attenuation) knobs on the amp. I used 1/4" to TS connectors. I wonder if it's there?


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Strange... my horns are 112db efficiency, and mine were dead silent with my P2500s amps when i had them. My P7000s amp is dead quiet with the Danley DTS-10 too.

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post #24 of 59 Old 12-16-15, 11:37 PM
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Re: Is Your System's Noise Floor Low Enough?

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Strange... my horns are 112db efficiency, and mine were dead silent with my P2500s amps when i had them. My P7000s amp is dead quiet with the Danley DTS-10 too.

I remember you saying that. That's partly why I was so surprised to hear noise. It doesn't change amplitude so I feel like it's not in the pre stage. Puzzling, and frustrating. Btw Ron, no regrets buying this amp. Despite the noise, it has still changed my space for the better. That's also why I need to get a handle on this.


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post #25 of 59 Old 12-16-15, 11:50 PM
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Re: Is Your System's Noise Floor Low Enough?

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I remember you saying that. That's partly why I was so surprised to hear noise. It doesn't change amplitude so I feel like it's not in the pre stage. Puzzling, and frustrating. Btw Ron, no regrets buying this amp. Despite the noise, it has still changed my space for the better. That's also why I need to get a handle on this.


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It could just be noise on the AC lines coming from all sorts of who knows where. You may want to try moving all 4 of your dedicated 20 amp circuits to the same leg on the panel if it's not done so already.

Like mentioned this can come from anywhere.... even the neighbors house since all residential shares feeds.

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post #26 of 59 Old 12-17-15, 12:22 AM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

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I remember you saying that. That's partly why I was so surprised to hear noise. It doesn't change amplitude so I feel like it's not in the pre stage. Puzzling, and frustrating. Btw Ron, no regrets buying this amp. Despite the noise, it has still changed my space for the better. That's also why I need to get a handle on this.


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I just reported in this thread that the Furman PST-8D power conditioner that I just got has solved (still have to measure to confirm) the HDMI noise problem from the music server. Your problem might just be noise from one component getting into another through power. Furman conditioners are good at eliminating HF and RF noise problems.

Also, don't forget to try a ground isolation plug.


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post #27 of 59 Old 12-17-15, 06:41 AM
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Re: Is Your System's Noise Floor Low Enough?

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I just reported in this thread that the Furman PST-8D power conditioner that I just got has solved (still have to measure to confirm) the HDMI noise problem from the music server. Your problem might just be noise from one component getting into another through power. Furman conditioners are good at eliminating HF and RF noise problems.

Also, don't forget to try a ground isolation plug.
Please do not defeat the ground of the equipment or recommend it. It's a safety hazard.

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post #28 of 59 Old 12-17-15, 07:00 AM Thread Starter
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Please do not defeat the ground of the equipment or recommend it. It's a safety hazard.
As Talley says, it can create a safety hazard. If you try it, do so with great care. If you do not know how to approach it safely, do not try it. All due respect, I would not suggest it if I thought it was a real great risk. Ground loops are a common cause of noise in audio systems, and isolating or lifting grounds is a common way of diagnosing and trying to solve such problems. A lot of modern equipment does not even have the third wire ground, by design, to help prevent ground loop problems.

A good power conditioner like the Furman, is probably a better solution all around , in that it breaks the loop effectively in the frequency range concerned with filtering, all with perfect safety.


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post #29 of 59 Old 12-17-15, 09:45 AM
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Re: Is Your System's Noise Floor Low Enough?

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As Talley says, it can create a safety hazard. If you try it, do so with great care. If you do not know how to approach it safely, do not try it. All due respect, I would not suggest it if I thought it was a real great risk. Ground loops are a common cause of noise in audio systems, and isolating or lifting grounds is a common way of diagnosing and trying to solve such problems. A lot of modern equipment does not even have the third wire ground, by design, to help prevent ground loop problems.

A good power conditioner like the Furman, is probably a better solution all around , in that it breaks the loop effectively in the frequency range concerned with filtering, all with perfect safety.
I've been doing alot of research on the ground loops and general noise. I am a master electrician for Texas, went through 5yrs of training... and have 15years of experience. I'm extremely educated in AC circutry and also work in the Petrochemical industry for the past 10yrs for an instrumentation company where we install automated DCS systems typically with 24v systems dealing with milli-amp controls. Isolated grounds, reference grounding, shielding, etc.... over the years I've grown to see alot in the industry. My background is commercial/residential service work, new construction commercial and again past 10 years petrochemical. I by no means am any expert but I do consider myself to be successful in my career and very knowledgable. One thing that I must admit is I am by no means any expert on A/V equipment INTERNAL circuitry. I am researching because I want to become a good source of information so I can assist others on this site with any issues. I am however not an electrical engineer so please keep that in mind.

With that being said one of the best articles I can recommend anyone reading is this one:

http://www.surgex.com/pdf/PowerGround.pdf

most all noise.... can be eliminated through proper grounding. Some devices only promote. UPS equipment being one of them. I've designed my power system feeding my equipment to be that of an isolated ground type. It works... when done right. Noise you are hearing are without a doubt caused by something... and typically it's the noise on shields and/or high frequency noise on the a/c line being present because the grounding system is not up to par to dissipate this.

People think I'm nuts for my power system... but it works. Here is my dedicated panel showing the isolated ground bar.... where I have dedicated grounds going to each receptacle in my system traveling back to a main bus. This bus is isolated from earth ground in the panel using isolation mounting blocks and this ground bar is connected to the ground rod outside where the earth ground is also connected. My ground rod(s) are the main common point and this connection is IN THE GROUND. I have both the isolated ground wire from the busbar and the common earth ground wire from the panel attach to a single ground rod that is kept very short and uses a large #2 cable. Then I have TWO more ground rods installed forming a triangle that are spaced 10' apart and those are connected together using a 2/0 cable.

I do not use surge protection and do not use UPS equipment.
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post #30 of 59 Old 12-17-15, 10:55 AM Thread Starter
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Re: Is Your System's Noise Floor Low Enough?

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...most all noise.... can be eliminated through proper grounding.
I completely agree. And the grounding system you describe sounds exemplary, and it is always better to keep noise low through using such practices, but I am also confident that very few listening or home theater rooms have a grounding system like the one you describe. Just like most rooms do not have ideal acoustical symmetry or ideal acoustical treatment. In the case of grounding, it promotes a quiet system while being safer than lifting grounds, another good reason to do it that way, but even so there are probably only a few who would go to the trouble.

It is a reality in our hobby that few users have the luxury of having ideal anything in their systems. Most start from a best they can do on a budget perspective and have to do some bandaid work from there. But your description of an ideal grounding system is much appreciated and is useful for all to keep in mind as the ideal and as a goal when the opportunity arises.

Quote:
Some devices only promote. UPS equipment being one of them. I've designed my power system feeding my equipment to be that of an isolated ground type. It works... when done right. Noise you are hearing are without a doubt caused by something... and typically it's the noise on shields and/or high frequency noise on the a/c line being present because the grounding system is not up to par to dissipate this.
I would not say that UPS equipment only promotes, implying that there is only downside and no upside. UPS in my case is for my Windows desktop machines - I have two - and helps prevent operating and file system corruption in the event of power outage. A well-designed UPS can be fairly quiet in terms of HF noise generation. Mine is used only for those two computers, the rest of my audio equipment runs on the same outlets/circuit but not off of the UPS.

I readily agree that typical UPS equipment can be a source of noise, and might not even keep a computer from shutting down the way it is supposed to. Mine is designed to provide a pure, low-distortion sine wave output when the input power disappears, and I have tested it to be effective in running my systems safely.

Another point not yet mentioned, that I learned the hard way (a long, painful story) is that all of the equipment in an audio and/or computer system should run off of the same power phase. Most homes are supplied from a 240 V two-phase transformer. So there are two phases available in a house at its outlets. Without a voltmeter, one cannot tell if two sets of outlets, even in the same room, are on the same phase or on the opposing phases. I always check with a voltmeter. Measuring from hot to hot will show the 240 V value if two sets of outlets are on opposing phases. This can cause noise and even equipment damage where sensitive inputs in equipment on one phase are driven from outputs on the opposing phase. Some will argue that it should not be a problem, I can testify from first hand experience that it can be a cause of equipment damage.

Talley, I appreciate your post and your comments and perspectives, and I am not arguing with anything you have said - except on the UPS point a little - simply clarifying a few points.


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