AC Polarity and the reduction of noise and hum
- Thread starter marty
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Here is something to add to this. It's Rane's excellent Tech Note about system grounding and the differing combinations possible. It is also well understood the problem is no industry standard. I have 4 systems currently operating and hands down the quietest of the 4 is the completely balanced system. Not saying the others are excessively noisy but any system I have to put my ear at the edge of a midrange horn to hear any noise at all is darn good!
Rob
this is the famous aes48 which tells you what to do with pin 1 of the xlr cable in balanced connections (connect it to the chassis at both ends). in my ayre amp, this is not the case so i connect the chassis to the earth ground with good results. mr pass appears to be not that fond of this 48 either in this dated thread over at diyaudio (http://www.diyaudio.com/forums/pass-labs/117444-xlr-pin-1-question-chassis-vs-circuit-ground.html)
i like the PIMMS a lot and i have a few lying around if anyone wants to borrow or buy one of them. all schuko models. i thought they were isolation transformers though.
Isolation Transformer is a great way to reduce noise on power line.
Here my project based on an Isolation transformer with electrostatic shields and Furutech Receptacle.
Lol,
You hit 2 at once .
Free flow for electrons, plus mass loaded resonance control.
I remember a plant i worked , there they didnt lock a big roll up with large diameter copper cable
They use to cut off a meter day until it was empty , and stripped IT and delivered IT to a metalscrap at then 5 euro a kg copper price
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Now we are cooling with oil! Dan, I want to be in your camp! Let me know if there are any hazing rituals I need to go through first.
Steve williams
Site Founder, Site Owner, Administrator
lol yes noticed the nails only later .
Its beautifully made however.
To keep on topic i never look at polarity plugging in a powercable, which probably makes me a sinner
Its beautifully made however.
To keep on topic i never look at polarity plugging in a powercable, which probably makes me a sinner
I do however change polarity in the x over as phase shift (can ) occur due to the filtering components used , anyone interested in a good explanation on X overs / phase shift .
If a speaker is not wired properly it can cause loss of out put at a certain freq( x over area ) , making the sound dull /not dynamic , its basically " loss of energy ".
For example , when i see a LS with a 5 db dip at the x over point i view it as a design mistake , first the sound is not linear over the FR band secondly there could be ( doesnt have to be ) cancelling out( making the sound dull ) .
Thats why i would never buy a LS that is only designed by ear
what is phase shift?
Phase is the timing of a signal, and the shift is the degree of the delay that occurs on the signal when passed through a crossover. Each order of crossover introduces a 90 degree phase shift. A 180 degree shift is an inverse of the wave. If 2 speakers are 180 degrees out of phase then they will cancel each other wherever they produce the same frequencies. Even with crossovers, both speakers will produce sound for several octaves beyond the crossover point. If this problem occurs, there will be a noticeable dip in the frequency response at the crossover point. To solve this problem, wire one, but not both, of the speakers backwards (+ to -). Usually, phase shift problems only occur with 2nd order (or 6th order) crossovers, but can also occur when using multiple 2-way crossovers in a 3-way (or more) speaker system. The only way to really find and fix a phase shift problem is trying all possibilities in reversing the speaker leads. If reversing the leads makes the system sound louder, then you know you have fixed the problem.
http://www.diyaudioandvideo.com/Guide/WireSpeakerCrossover/
If a speaker is not wired properly it can cause loss of out put at a certain freq( x over area ) , making the sound dull /not dynamic , its basically " loss of energy ".
For example , when i see a LS with a 5 db dip at the x over point i view it as a design mistake , first the sound is not linear over the FR band secondly there could be ( doesnt have to be ) cancelling out( making the sound dull ) .
Thats why i would never buy a LS that is only designed by ear
what is phase shift?
Phase is the timing of a signal, and the shift is the degree of the delay that occurs on the signal when passed through a crossover. Each order of crossover introduces a 90 degree phase shift. A 180 degree shift is an inverse of the wave. If 2 speakers are 180 degrees out of phase then they will cancel each other wherever they produce the same frequencies. Even with crossovers, both speakers will produce sound for several octaves beyond the crossover point. If this problem occurs, there will be a noticeable dip in the frequency response at the crossover point. To solve this problem, wire one, but not both, of the speakers backwards (+ to -). Usually, phase shift problems only occur with 2nd order (or 6th order) crossovers, but can also occur when using multiple 2-way crossovers in a 3-way (or more) speaker system. The only way to really find and fix a phase shift problem is trying all possibilities in reversing the speaker leads. If reversing the leads makes the system sound louder, then you know you have fixed the problem.
http://www.diyaudioandvideo.com/Guide/WireSpeakerCrossover/
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im on the fence with balanced vs single ended..,I have owned many components that sound better with either scheme..I prefer to have both in a component , but if not , I would generally choose a RCA single ended device as the rca plug is ubiquitous.
DDK and MikeL use single-ended interconnects.
Jim White -- can there be any serious question whether Jim is qualified to opine on the sonic results of the Io -- I believe prefers the balanced connections on the Io. Vladimir Lamm obviously believes in single-ended. Flemming advocates balanced connections.
The argument that single-ended should not be used for long interconnect runs because you have a small amount of voltage drop seems silly since one can simply raise a volume control a litte bit to compensate.
The view that balanced connections cancel even-order harmonics but not odd-order harmonics seems more damaging, if this is true. Is this true?
In conclusion, we have another important topic which is clear as mud!
Jim White -- can there be any serious question whether Jim is qualified to opine on the sonic results of the Io -- I believe prefers the balanced connections on the Io. Vladimir Lamm obviously believes in single-ended. Flemming advocates balanced connections.
The argument that single-ended should not be used for long interconnect runs because you have a small amount of voltage drop seems silly since one can simply raise a volume control a litte bit to compensate.
The view that balanced connections cancel even-order harmonics but not odd-order harmonics seems more damaging, if this is true. Is this true?
In conclusion, we have another important topic which is clear as mud!
DDK and MikeL use single-ended interconnects.
Jim White -- can there be any serious question whether Jim is qualified to opine on the sonic results of the Io -- I believe prefers the balanced connections on the Io. Vladimir Lamm obviously believes in single-ended. Flemming advocates balanced connections.
The argument that single-ended should not be used for long interconnect runs because you have a small amount of voltage drop seems silly since one can simply raise a volume control a litte bit to compensate.
The view that balanced connections cancel even-order harmonics but not odd-order harmonics seems more damaging, if this is true. Is this true?
In conclusion, we have another important topic which is clear as mud!
Yes, which is why balanced can sound worse vs single ended. IMO, balanced only works out in the context of super-low harmonic distortion systems so when the evens are canceled the odds don't dominate the sound and make it annoying and mechanical sounding.
DDK and MikeL use single-ended interconnects.
Jim White -- can there be any serious question whether Jim is qualified to opine on the sonic results of the Io -- I believe prefers the balanced connections on the Io. Vladimir Lamm obviously believes in single-ended. Flemming advocates balanced connections.
The argument that single-ended should not be used for long interconnect runs because you have a small amount of voltage drop seems silly since one can simply raise a volume control a litte bit to compensate.
The view that balanced connections cancel even-order harmonics but not odd-order harmonics seems more damaging, if this is true. Is this true?
In conclusion, we have another important topic which is clear as mud!
Voltage is not the reason, nor is bandwidth loss; noise coupling is the primary reason long single-ended runs are usually avoided. See earlier posts.
Differential circuits cancel even order harmonics, not odd, true, but remember both components are very small. A single-ended circuit's distortion is typically dominated by the second harmonic distortion term; cancel that, and you haven't increased the third, but it is now dominate without the larger second harmonic.
There are pros and cons to both but in general, at least theoretically, balanced will provide superior performance, with the potential costs including greater power and complexity (not always true). A lot of designs include differential circuits along the way even if only internally.
Implementation matters, of course...
HTH - Don
Don gave the precise and exact answer. But to expand, the drop in voltage we worry about here is in the shield of the RCA/unbalanced connection. That drop in voltage will by definition cause a flow of current (it is like titling a full cup of water). Since the source of that voltage is mains, the shield is now dancing up and down with the frequency and harmonics of mains.
The above by itself is not a problem in differential/balanced connections. In unbalanced however, the signal, the center pin of RCA, is in reference to the shield. If for example you output nothing and the shield is dancing up and down, the receiver "hears" the dancing up and down as the signal. Hence the reason you hear hum or buzz (harmonics of mains).
In differential interconnects, there are two wires independent of the shield that carry the audio signal. As a result they are immune to vagaries of voltage drop in the shield, or differential in voltage between the chassis of two pieces of audio equipment (topic of this thread). It is absolutely superior to using unbalanced connection.
To give you a specific sense of this in an example, simple math shows that enough current flows in the shield of of an unbalanced connection can cause your signal to noise ratio to drop to poultry 70 db. That is just 12 bits of resolution! The same exact system/situation over balanced connection will boost the signal to noise ratio to whopping 130 db! Well beyond 96 db of 16-bit CD for example and beyond anything we can reproduce (analog or digital).
Balanced interconnects are trivially implemented using solid state electronics. The cost is in the noise in class of product we are discussing, pun intended
. Tube amp manufacturers don't want to use this solution likely because then the whole path is not tube. So it has been turned into a feature: "single ended sounds better." Well, it doesn't if you don't want your signal to be accompanied with tons of mains signal mixed in it.Members here go to heaven and hell to try to deal with "grounding issues." Yet they go and use single ended interconnects where it nicely carries and dumps mains related distortion into their audio path! It makes no sense.
RCA connections were invented to interconnect equipment in the same box. Never was it intended to go many feet to monoblock amps by speakers which is so common here.
Thankfully we are deaf as a stomp when it comes to low frequencies so that is the reason there is not as large of a cry as it should be. Still, if you sweat all the details, and your RCs are going the distance, you need to use balanced interconnects if you have any hope of staying true to the source music.
DDK and MikeL use single-ended interconnects.
Jim White -- can there be any serious question whether Jim is qualified to opine on the sonic results of the Io -- I believe prefers the balanced connections on the Io. Vladimir Lamm obviously believes in single-ended. Flemming advocates balanced connections.
The argument that single-ended should not be used for long interconnect runs because you have a small amount of voltage drop seems silly since one can simply raise a volume control a litte bit to compensate.
The view that balanced connections cancel even-order harmonics but not odd-order harmonics seems more damaging, if this is true. Is this true?
In conclusion, we have another important topic which is clear as mud!
Ron,
The topic will stay clear while you do not mix the technical aspects with preference, and particularly how we should check preference ...
Amir is what you saying is that THD is proven to be lower on balanced amplification versus single ended amplification??
Amir,
If we use something like an Interocitor from Steve McCormack in between the SE preamp and the Balanced amp...does this work in your opinion? I have heard nothing but great things about it from Gary Koh and Microstrip.
In our case, i do hear a little noise which i suspect is from the 'grid' of the house...but tube noise is greater...and i still need to stand next to the tweeter with my ear actually perpendicular to hear this noise when the entire room has no lights on, no music playing, etc. Nevertheless, as an audiophile, i have to ask!
If we use something like an Interocitor from Steve McCormack in between the SE preamp and the Balanced amp...does this work in your opinion? I have heard nothing but great things about it from Gary Koh and Microstrip.
In our case, i do hear a little noise which i suspect is from the 'grid' of the house...but tube noise is greater...and i still need to stand next to the tweeter with my ear actually perpendicular to hear this noise when the entire room has no lights on, no music playing, etc. Nevertheless, as an audiophile, i have to ask!
No, I am actually completely staying away from the internal architecture of an amplifier. All we are discussing is how audio is transmitted between two pieces of audio equipment. This can and is routinely implemented in balanced mode regardless of whether the amplifier itself is single ended or balanced.
As an aside, THD is perceptually blind so it is not a useful measure of audible distortion.
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