Axiom Home Page Forums General Discussion Technical Questions Who can solve this problem?

Well Randy, as I said when I suggested that you put the closet light on while listening, I continued to read this and ponder, but nothing sensible resulted(the closest was that the Emotiva brought evil spirits into the closet which were subdued by the friendly spirits activated by the lights).

I'll comment on some of your other points. It isn't unusual for there to be a very low mechanical hum from the transformer when you put your ear just above the top vents. The three receivers that I use do this, but it isn't audible a couple feet away. The alternating magnetic fields in the transformer can vibrate the laminations in tune with the 60Hz power. A toroidal transformer, such as those the Emotiva uses, is supposed to be less susceptible to hum because the core is more tightly wound. My stuff can't be heard beyond a few inches, so it's effectively noise-free, and I'd think that the same would apply to the Emotiva.

As to the electrical(as opposed to mechanical)hum or hiss at a very low level heard with your ear next to the speaker, again with my receivers turned up to maximum gain(with nothing playing, of course)a faint hiss from the tweeters and faint hum from the woofers is heard a few inches away, but there's nothing at the level settings that are commonly used. So, in effect the equipment is both mechanically and electrically noise-free and isn't a cause for concern.

Here are the pics of the breaker box. There is a bar on both sides, connected by some type of strap at the bottom, all hooked to the heavy black cable on the top right next to the main power breaker that feeds the entire system. The second picture shows how the are all screwed down to the ride side. The left side is similar. I find it hard to believe it is wired wrong, we've lived hear for 4 years and have had no issues. Also, all electricians in Iowa, Illinois, etc. belong to the Union and are certified and must follow strict building code guidelines. You guys really think this is incorrect?

ps: nevermind the cheap power bar to the right, that just powers my DSL wireless modem and network router which is hooked to a 110 block.

Thanks John, I feel better knowing the low electrical hum from the woofers and hiss from the tweeters (faint with ears very close) may be normal. I also hear it with the Denon, so it must not be the amp.

The static issue is really getting stranger, the more troubleshooting I do. Today I turned every breaker off, one by one in the entire house. When I was done, the only breaker on was the 20amp feeding my HT area. There was still static in the tweeters, just like when I have the other 15amp light circuit on with the closet light on.

I thought I was onto something, but soon got more confused. I checked the lights on the ceiling of the closet which are connected to the closet switch. The lights are just the cheap ceramic kind you get at most improvement stores for closets.

Anyway, I turned the power off to the 15amp circuit so I could look at the wiring. For light so I could see what I was doing, I used my halogen work light and ran a long extension cord to another part of the basement for power. The first light checked out ok, so I proceeded to look at the second light at the end of this switch circuit. I noticed I only had the black and white wires hooked up. These ceramic lights have two gold screws for power, and two silver screws for neutral, but really don't have a green screw for the ground, like switches and outlets.

So I thought since the neutral and grounds come togethor back at the circuit box, I would try hooking the ground to the other silver screw. Once done, I jumped down and ran over to the speaker. YESSSSS the static was gone.

But, my excitement quickly ended when I turned off the halogen light, the static came back. WHAT, how can this be, it doesn't make sense.

What is really funny is, I can set the halogen light just inside the door turned on, and the static goes away. If I move it outside the closet door a few feet the static comes back.

It is almost like there is some darn force field at my doorway to the closet. If there is a light source, closet or other source, the static goes away when the light is powered. I'm going nuts.

The closet dimensions are probably 4ft x 12ft, very long and narrow. When you first walk in the door there is a switch which powers two 60watt bulbs, one at each end of the closet. The AV stuff is at the other end.

Sounds very frustrating Randy- I'm sorry. I know you'll get to the bottom of it. Look on the "bright" side (pun intended) - if we don't figure it out you can start selling the latest greatest snake oil product: "The audio purifying bulb" and make yourself rich

Thanks for posting pictures of your panel (and the amp in the other thread- very nice ) Not that I've seen tons of panel installations, but I'm confused by what I am seeing. Those two bars full of screws down each side look like the neutral bus, connected together with the strap at the bottom as one would expect. I wish I could enlarge the pic more, but it sure looks like the grounds are connected to the same bus?!? I've never seen this before myself. Although I can't make out a separate grounding strap where the grounds should go.

Strange to me, but I'm no expert. Hopefully some of the others with more knowledge on this can make better sense of it.

One thing I know for sure, we need to resolve this quick so you can get back to more important things, namely enjoying the system instead of this headache. Oh, and I think I speak for all of us when I say... "bring on the pics of the new speakers!"

Dave, they already beat Randy to it .

Well here is a paragraph out of the book I purchased from Menards when I wired my basement. According to this the neutral AND bare and/or green wires connect to the neutral bar, which ultimately hook to the ground going to the ground rod in the yard.

"The main neutral wire is connected to the neutral bus bar. This bar is connected to a system ground wire, which leads to a grounding rod. White wires for every circuit, and possibly bare or green ground wires, also connect to the neutral bus bar. As a result, each 120-volt circuit has a black or colored wire leading from a circuit breaker, a white wire leading to the neutral bus bar, and possibly a bare copper or green-covered ground wire also connected to the neutral bar. "

this comes form the step-by-step guidebook on Home Wiring

ps: funny thing is Dave, The publishing information is from PO Box 70865, Salt Lake City, Utah 84170

Very interesting Randy. It sounds correct according to the book for sure. I haven't seen it in my area, but as I said before I'm no expert so there for sure is much I don't know.

I knew that eventually both are connected back to ground, but in my case it isn't done at the panel. I believe it is back at the main service/shutoff panel which is on the outside of the house with the utility co. power meter.

Silly about the location of the publisher on the book. I guess the local electricians here get there books elsewhere.

John, wow! Good find. It does look like the same type of idea. There you go Randy, for only $100 you can convert line noise into light.

Hi Randy

You've got great advice from everyone in this thread about troubleshooting circuits but as I thought it might be worthwhile taking another look at the amp itself. I've never heard it so I checked the specs which generally look pretty good but this commentary about the signal to noise ratio caught my eye. As we all know the M80s are very transparent because they are so linear so those tweeters will be more sensitive to any HF noise. The following discussion was from the Audioholics article. Gene DellaSalla's measurements showed an unflattering noise profile for this amp.

"Signal to Noise Ratio (SNR) Measurements

Measuring the Signal to Noise ratio of this amplifier proved to be quite challenging due to the lack of proper LPF for limiting the bandwidth to below the switching frequency.

By applying A-weighting response curve, I was able to achieve partially reasonable measurements of 82dBA (A-wt) at 1 watt or about 102dBA at 270wpc.

From Emotiva Engineering Labs:We perform my signal to noise ratio test a little different than you do. We base our measurement strictly on the rms voltage as measured on the AP with a <10Hz to 30Hz bandwidth selected. No other weighting is applied. The amplifier is connecting to a purely resistive load, in this case 4 ohms. We measured a noise floor voltage of 268uV using the balanced output of the AP with a 50 ohm output impedance - generator selected to off to terminate the input to the amplifier. From this starting point we let the AP do all the work. We select the output level from which I want the S/N ratio to be referenced at and call that the 0dB point. Below are some measurements we have taken:

102dB ref 300W
101dB ref 270W
87 dB ref 10W
77dB ref 1W

These numbers should be more consistent with what you are hearing from the amplifier. Also, we believe these numbers represent a best case scenario because we are using the balanced input. The key to this test is the noise floor of the amplifier. This can change significantly if power cables are inducing 60Hz into signal, other equipment could be radiating noise, etc.

In any event, the 77dB @ 1 watt number isn’t flattering to say the least, but given the unique amplifier topology, I suspect the out of band switching noise is producing a non representative number since noise was never an audible issue in real world listening tests. When using the Yamaha RX-V2500 as the preamp for the Emotiva MPS-1, the set-up was dead quiet and sounded as silent as other amps I have measured with significantly lower noise floors. "

I also noticed that he ranked the signal to noise ratio lowest among his performance parameters. I know you tested the Denon as well but it may be worth focussing on the amp itself as a noise source. Sometimes its a compatiblity issue with the pre-amp. If you were nearby I'd lend you one of my Brystons for comparison.

http://www.audioholics.com/productreviews/avhardware/emotivaMPS1p5.php

Bump