Noise

[speakerman1]

I have some other places I go to to discuss things. This is a big subject. It is our worst enemy. There are different types of noise. Distortion is one. There are other noises. Those lines of flux create noise. You guys in the PL threads talk about it ; but a lot don't read the threads. I don't know if you read other threads. I have seen some described that I have never have heard of. In audio years I'm pretty new at this. AC noise is another. The AC noise is a big one. I don't know what RF noise is.

I hear noise 24 hours a day. I have ringing of the ears. It is sort of like the old joke. If a tree falls in the woods and no one is there to hear it does it make a sound? Does it make a noise? If I can't hear the noise is it there? The next time I take a hearing test I will ask for the print out. When I ask questions I may seem like a jerk. If so I apologize. Just because your system does it doesn't mean all systems do. Just treat me as the ignorant person I am. Please explain it to me.

How do you deal with AC noise? How do you deal with noise at all? Wires is a curse. The can make and also pick up noise. Make it your goal in this life to prove me wrong. Slap me like a red headed step child that I am. In the last week I have discussed dedicated wiring in your house, no transformers, DC power supplies, filters, wires, the service in your house and grounding. Grounding can cure a lot of ills in a system. I'm sort of a purist in my thinking. Less is better. I have one IA. I think a component doing one thig is better than making it do a bunch of things.

Lee the resistor may fix the problem. My thinking is what is causing the problem? Wouldn't figuring that out and fixing it be a better fix? It always goes back to less is better with me.

Larry

 

[laatsch55]

It's a case of the ungrounded potential finding the easiest way back to ground. By using a rtesistor in PARALLEL, not series it makes it harder for the potential to take thaty path so it takes the path less resistive.

 

[speakerman1]

Why is it though? You ain't getting off that easy. LOL

Larry

 

[speakerman1]

I guess what I was getting at is what tools do you use to try and get rid of as much noise as possible?

Larry

 

[Pure_Brew]

First off, the most important noise for me to deal with are simply the mechanical induced noises that can occur in power transformers, relays and transport/source mechanisms.

In one amp I eliminated relay hum by building a DC supply to feed just the relay. The hum was induced by AC, which causes the relay to want to open and close 60x a second. Not going to be an issue for most amps I imagine.

On transformer hum, I used the PS Audio Humbuster and it works, but mainly on toroids. I don't fully understand the function, but there can be distortion at the zero-cross on the AC waveform. I believe laatsch mentioned transformer relocation/rewire can work within the amp that has this issue. Looks like they don't make it anymore, along with a bunch of other things.

On transports/source I suppose I would chose just based on audibility. I chose a lower priced Marantz CDP over a much more expensive NAD CDP due to the fact I could hear the NAD spinning from across the room.

As far as noise in a system that is audible through speakers, I find that stacking components, AC cords too close to signal cords and CATV systems not properly grounded can be sources of noise. These are all easily remedied.

Components that induce noise all on their own as heard through the speakers has been beyond my ability to troubleshoot and remedy, other then getting rid of them. Once this occurs, I have also never found line filters at any price that would fix those issues. Also, unless the analog RCA cables are complete trash in a system, I don't typically find noise issues there.

 

[laatsch55]

To a certain degree Larrt, an amplifier's design is going to dictate it's noise floor.Power supply design and type, output topology, v/a stage type, all have certain methods to deal with noisde.S

Starting with the AC mains in, an "X" cap[acotor should be placed accross the transformer primary pair. This keeps RF emissionsnot internal to the amp to a minimum,. The bridge rectifier needs "snubbing" caps to

 

[speakerman1]

What is RF emissions?

Larry

 

[speakerman1]

Never mind I call it something else. EMI Have done some reading this AM. I had a misunderstanding of ferrite beads. Learning today. Here is some reading.
http://www.jensen-transformers.com/an/g ... eminar.pdf

Larry

 

[laatsch55]

I fell aslep in the middle of my post. I'll finish it tonight.

 

[speakerman1]

This is what I was taught.

http://en.wikipedia.org/wiki/Transformer.

Also EMI is the result of EMF.

http://en.wikipedia.org/wiki/Electromagnetic_field

Larry

 

[speakerman1]

Here goes a big question. When using shielding. Do you guys ground the shielding? We even had a procedure to do it. You cut a slit in the insulation and pull the shield through it. Twist then termiate it. We keep as much insulation intact. It goes under the clamp of the canon plug. Then it is stripped and the wires terminated You may be doing a 50 pin CP. The wire is only one inch long after the insulation. Wow went around the hill to get there didn't I? Here is the question. Has anyone ever tried keeping the AC and DC grd.s separate? Just thinking. I probably have asked before. I think a DC ground to the case. The AC grd.s to a separate component. Like the grd lug on the pwr cond.

 

[NavLinear]

Here are some photos of a cable I had on my desk that show one of the techniques for terminating a shield to ground. We used a solder sleeve with a wire attached to the solder ring that - when heated it will solder this wire to the shield. Both ends seal with a material that has a lower melting point than the sleeve providing an environmental seal.

There are different schools of thought regarding the grounding of the shield. One common method is to float the shield at one end of the cable and tie the other end of the shield to ground. Another is to tie both ends of the shield to ground. With higher frequencies I've seen situations where the shield was tied to ground at four foot intervals - the signal on the center conductor created havoc with signals on adjacent wires when the shield wasn't terminated in this manner.





We have used two seperate grounds for analog and digital sections to isolate them from each other in some of the designs I've been involved with. These grounds are normally tied together at some point - typically at single point ground (aka star ground). Lot's to read on the subject.

I think you think too much!

 

[speakerman1]

I have hum. So I am trying to isolate it. Mostly on phono. I may have to crank it. But it is there. If I'm awake I'm thinking. LOL

 

[speakerman1]

We never terminated to the back shell. You know what the blue lines on the splice are for? I have those type splices. Work slicker than snot on a door knob. LOL

 

[speakerman1]

Well you could test to see if the question to be is to float or float not? We terminated to pins. Doing mods you wear out burnishing brushes. Just think if you didn't have static wicks. I wouldn't be running to ground it. Even the fuel nozzle gets grounded and the truck gets grounded. Every piece of equipment gets grounded. you think 120 60 cycles is bad. Try it at 400 cycles. It don't make you jerk back. It hurts bad enough to make you walk away and go to the bathroom before you pee yourself. Working around a hot aircraft isn't fun. You drop a screw. You aren't leaving it. If it doesn't trip something going to who knows where.