Hi!
I'd like to diy a balanced power station. Several years ago I did one with a 1000va (230/2X115vac) EI transformer and tried it with a cd player and a little 50w class AB amp. So it was big enough but the result wasn't good: lost of weight and the music life was gone!
But I believe that this technology can work fine: does somebody construct his own balanced power station with the same quality result as Equitech (for example)? What do I have to tell to the man who would wound the balanced transformer to get the right quality?
thanks for sharing your secrets!
I'd like to diy a balanced power station. Several years ago I did one with a 1000va (230/2X115vac) EI transformer and tried it with a cd player and a little 50w class AB amp. So it was big enough but the result wasn't good: lost of weight and the music life was gone!
But I believe that this technology can work fine: does somebody construct his own balanced power station with the same quality result as Equitech (for example)? What do I have to tell to the man who would wound the balanced transformer to get the right quality?
thanks for sharing your secrets!
Jon_Risch's Web Site
Have you looked at this? I have been using 2 Signal SU-2 balanced with a technical ground now for several years on source and amps. I switch back to "standard" power on occasion but for me the balanced gives a blacker back round, I find the overall sound to be cleaner.
A Signal SU-2 is a big ugly chunk of iron.
Have you looked at this? I have been using 2 Signal SU-2 balanced with a technical ground now for several years on source and amps. I switch back to "standard" power on occasion but for me the balanced gives a blacker back round, I find the overall sound to be cleaner.
A Signal SU-2 is a big ugly chunk of iron.
The secondaries should be bifilar wound so there is equal capacitance between each coil and ground. This is so the high frequency noise theoretically cancels. Probably easiest to do on a toroid core. Go large on the core.
High frequency noise flies right through bifilar windings, when compared to split bobbin or electrostatic shielded transformers. Have had best success with shielded isolation transformers. Besides the fact balanced power is an NEC violation in residential service (which no one seems to care about) it will not provide any significant benefit over a standard isolation transformer serving properly designed equipment.
This argument has been beat to death in other threads, and never goes anywhere.
Look into how they build isolated power for surgery rooms to understand which type of transformer design works best for high isolation and low noise. No toroids there.
This argument has been beat to death in other threads, and never goes anywhere.
Look into how they build isolated power for surgery rooms to understand which type of transformer design works best for high isolation and low noise. No toroids there.
National Electric Code. Obviously only applies to the US, but there is strong correlation in general to other countries, as codes place safety high on the priority list. Balanced power is restricted to commercial use only, and even then there are a number of specific requirements that must be met in order to comply.
Not that I am the Code Cop, and insist we all be conformists, but it is telling that those who choose to use balanced power in the home normally fail to meet the numerous other requirements that are listed in order to provide for a safe installation. I have yet to hear of or see anyone's residential installation that complies. You will usually get a claim that "I know what I'm doing" therefore no worries.
When having to decide between a boring, old-fashioned isolation transformer with fresh neutral bond versus a 'new' exciting method of balanced power that few are using, it is the fashionability that wins out, rather than the practical and effective solution that is also legal. I would challenge anyone that can prove balanced power is an improvement over isolated-bond that either they are a victim of psychological effects, or they have connected equipment that is poorly designed.
Not that I am the Code Cop, and insist we all be conformists, but it is telling that those who choose to use balanced power in the home normally fail to meet the numerous other requirements that are listed in order to provide for a safe installation. I have yet to hear of or see anyone's residential installation that complies. You will usually get a claim that "I know what I'm doing" therefore no worries.
When having to decide between a boring, old-fashioned isolation transformer with fresh neutral bond versus a 'new' exciting method of balanced power that few are using, it is the fashionability that wins out, rather than the practical and effective solution that is also legal. I would challenge anyone that can prove balanced power is an improvement over isolated-bond that either they are a victim of psychological effects, or they have connected equipment that is poorly designed.
But with bifilar with equal capacitance, the noise can cancel. Electrostatic shielding is a must. Whether or not using toroid or split bobbin.
Balanced power is an NEC violation for house wiring to wall socket, but doesn't mean it can't be done in a plug-in device. NEC doesn't cover that.
To re state what I think you have said, balanced power created from a normal outlet feeding the transformer then feeding my equipment, is viewed by NEC differently than balanced power being fed directly to an outlet? If this is correct that's an important and welcome distinction. If I can confirm my meaningless balanced power solution is not a code violation, well just think how good that's gonna sound.
Common mode noise could care less about the balance of a winding. If I provide it with a big fat capacitor between primary and secondary, noise will travel right through it. Bifilar windings do not come close to the attenuation of a shield. Shielded toroids are fairly rare; I haven't seen too many off the shelf units, at least. Split bobbin does not require a shield, and I have never seen one with it. One of the reasons for split bobbin is to negate the need for a shield. Are we talking the same thing, here?
Shields are normally used when one winding is wound on top of another, called a concentric winding. It is an improvement over split bobbin in that leakage inductance is reduced due to improved flux linkage between windings. The shield is placed between the windings, shunting common mode noise to ground and effectively guarding the path between primary and secondary. Layered windings reduce leakage even further, with the detriment of higher capacitance between windings. It is difficult to impossible to shield multilayered windings. Bifilar is the acme of a layered structure; primary and secondary are wound together. Worst capacitance and best linkage. Impossible to shield. This is why good input transformers are not bifilar.
Toroid is unique, in that the purpose is less about winding/leakage performance, and more about reduction of magnetic stray. Without a shield capacitance is typically high enough that noise travels well between windings. The few times I use a toroid I always preface it with an EI or split bobbin isolation transformer, grounded secondary.
So each winding configuration is generally a tradeoff between leakage inductance versus capacitance. A shield will nearly eliminate inter-winding capacitance when it can be installed.
The NEC has jurisdiction over cord-and-plug connected equipment. It does not stop at the outlet- run that one by your local inspector. Additionally, the common desire for DIY balanced power is to have a big transformer provide power to an outlet strip; the multiple cord-and-plug connected audio equipment then plugs not into the wall, but into the outlet strip. You better believe the NEC has jurisdiction over that power strip and what feeds it.
What one chooses to do inside a chassis after going through a transformer located inside that chassis is another matter. You have great flexibility there.
Red herring. There are two secondaries, not one. The common mode noise is opposite phase in each, so they cancel in the ground line.
Dude said he was having one made. So he can add a shield. In any event, they are a common option on transformers at not much expense. And they are standard in any balanced transformer commercially available.
And that common mode noise then contaminates the ground line. The primary purpose of a balanced power supply is to provide a clean ground line.
The bifilar windings in a balanced power transformer are not the primary and the secondary. They are the two secondaries. They are NOT layers. The two secondary windings are wound together at the same time with side-by-side wires so that each winding will have the same capacitance, so that high frequencies will couple the same noise voltage to each winding for better cancellation. But then this is stated in just about every tech topic on balanced power.
So use a shield. Jeez!
The NEC is an installation standard, not a product standard.
I don't know why I bother trying to teach transformer fundamentals anymore.
Let's try a different approach- I used an isolation transformer once, and the sound became more liquid. That's what is needed to convince people.
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