Actually, Chris, they wouldn't. The R-core has the same single piece, gapless construction as the toroid. The difference is in the winding method. The toroid normaly requires a rather complex and interesting machine to wind it, while the R-core avoids this by the use of a round core cross-section, which alowes a bobbin to be assembled on the core in two halves. The bobbin itself has teeth on the sides like a gear, which are used to turn the bobbin on the core and thus wind the wire onto it. In all other respects save perhaps a slightly elevated stray flux, it is like a toroid. In fact, it is eminently possible to wind an R-core on a toroid winding machine, without bobins. Trying to cut the R-core is the same as cutting a toroid core, both are wound out of one piece of metal. Te difference is that with the R-core, the width is varied from end to end, so that when wound, the cross-section becomes circular.
You should not have anywhere near enough DC in your AC supply to cause core saturation in any type of transformer. If you do you need to get something done about it before something gets damaged or overheats and causes a fire! Please take that seriously.
The mechanical buzzing that a transformer produces is either caused by mangestriction or stray flux moving a magnetic surface, both poor design/manufacture, not core type. In my 30 years experience EI cores tend to produce more noise from both causes.
I'm not saying that a cheap torroid will allways be quieter than a quality EI.
Electrical noise introduced into the amplifier chain usually comes from; earthing issues, stray transformer flux, poor filtering or poor power supply rejection ratio.
If you are getting electrical HF noise into your amp check earthing.
If the electrical noise is caused by the transformer, encase it in a magnetic sheild, wrap it with a flux strap, use a toriod or do all, (though that may be over kill
Poor filtering and PSRR not a transformer issue.
All core types can saturate but should not do so, (see 1st parragraph). An EI core transformer with an air gap, (note manufacturers try to keep the gap as small as possible so that it's effect will be minimised), will often saturate before a torriods. It depends on how conservitively the core has been designed, not on the air gap.
I'm still to hear any advantage for an EI over a torroid.
OOPS, I'll admit it, there is an EI advantage; they're usually cheaper!
NOTE There are flux leakage transformers with large gaps, ie AC welders, discharge lighting, magamps... We are not discussing these types and they would not be suitable for an amplifier.
Sorry if I'm being a bit long winded, regards
Walker
Passionate, not heated
The mechanical buzzing that a transformer produces is either caused by mangestriction or stray flux moving a magnetic surface, both poor design/manufacture, not core type. In my 30 years experience EI cores tend to produce more noise from both causes.
I'm not saying that a cheap torroid will allways be quieter than a quality EI.
Electrical noise introduced into the amplifier chain usually comes from; earthing issues, stray transformer flux, poor filtering or poor power supply rejection ratio.
If you are getting electrical HF noise into your amp check earthing.
If the electrical noise is caused by the transformer, encase it in a magnetic sheild, wrap it with a flux strap, use a toriod or do all, (though that may be over kill
Poor filtering and PSRR not a transformer issue.All core types can saturate but should not do so, (see 1st parragraph). An EI core transformer with an air gap, (note manufacturers try to keep the gap as small as possible so that it's effect will be minimised), will often saturate before a torriods. It depends on how conservitively the core has been designed, not on the air gap.
I'm still to hear any advantage for an EI over a torroid.
OOPS, I'll admit it, there is an EI advantage; they're usually cheaper!
NOTE There are flux leakage transformers with large gaps, ie AC welders, discharge lighting, magamps... We are not discussing these types and they would not be suitable for an amplifier.
Sorry if I'm being a bit long winded, regards
Walker
Passionate, not heated
Hi walker,
In my experience with audio equipment, spanning over 30 years, I have formed an opposite opinion to yours with respect to core saturation.
I do agree that all transformers can be noisy. That includes toroids.
The only advantages a toroid can have are a lower profile (allowing less rack space to be used), and normally lower external flux.
I would be interested in hearing a good toroid as an output transformer, but I think that gapping would still be prudent. It's not a perfect world we live in.
-Chris
In my experience with audio equipment, spanning over 30 years, I have formed an opposite opinion to yours with respect to core saturation.
I do agree that all transformers can be noisy. That includes toroids.
The only advantages a toroid can have are a lower profile (allowing less rack space to be used), and normally lower external flux.
I would be interested in hearing a good toroid as an output transformer, but I think that gapping would still be prudent. It's not a perfect world we live in.
Well, saturation is a reality with mains transformers. Are you going to solve this on the distribution side, or your smaller transformer design? It's not a problem for heavy industry (that's where the money is), so I'm guessing the small transformer manufacturer had better start dealing with these issues. EI core types are not affected as much.
-Chris
G'day Chris,
are you experiencing core saturation due to supply spikes or DC offset? If it is because of DC it needs to be delt with.
Do you believe that EI core transformers handle saturation better because they have more core mass, because the have an air gap or for some other reason? The air gap in a mains EI is miniscule, as small as the manufacturers can make it. A high quality EI transformer will have a smaller gap than a cheap one. The air gap will not stop the transformer from saturating unless it is much larger.
By the way I'm only thinking of mains input transformers not impedence matching audio transformers. Audio tranformers have different concerns.
In your experience, you have found EI core transformers produce less magnestriction noise. Do I understand that correctly? We seem to agree on torroids having, in general, less stray flux. Though I think that a good flux strap on an EI normally handles stray flux effectively.
RDF; your posting on your brother's problem. I'm guessing that harmonics in the AC supply are more likely the problem not DC.
Regards Walker
are you experiencing core saturation due to supply spikes or DC offset? If it is because of DC it needs to be delt with.
Do you believe that EI core transformers handle saturation better because they have more core mass, because the have an air gap or for some other reason? The air gap in a mains EI is miniscule, as small as the manufacturers can make it. A high quality EI transformer will have a smaller gap than a cheap one. The air gap will not stop the transformer from saturating unless it is much larger.
By the way I'm only thinking of mains input transformers not impedence matching audio transformers. Audio tranformers have different concerns.
In your experience, you have found EI core transformers produce less magnestriction noise. Do I understand that correctly? We seem to agree on torroids having, in general, less stray flux. Though I think that a good flux strap on an EI normally handles stray flux effectively.
RDF; your posting on your brother's problem. I'm guessing that harmonics in the AC supply are more likely the problem not DC.
Regards Walker
EI and C core transformers has superiority over toroids in one aspect mainly: they can be made with minimum capistance between primary and secondary winding and also EI transformers aren't wideband transformers like toroids by the reason of bigger leakage inductance
-I know that it's also disadventage ( bigger magnetic field around transformer), but we don't always need to install transformer very close to supplied circuits.
-I know that it's also disadventage ( bigger magnetic field around transformer), but we don't always need to install transformer very close to supplied circuits.
Hi Walker,
I am in the service industry, so I see complaints from a wide range of customers and equipment. I also understand the technical aspects of each transformer type.
My own opinion is that each type of transformer has it's strengths, but recently (for a few years now) the toroid transformer has been touted as the perfect part for a mains transformer. This is not always true, and there are cases where an EI part is superior. I just have a problem with everyone blindly recommending toroids.
If you look at the construction of an EI type, you will notice that there are two gaps in each magnetic circuit. These gaps are substantial when compared to a gapless toroid transformer.
I haven't researched this, but I'll bet the core of an EI type runs cooler than a toroid as well due to the accessibility of the core itself. It is known that the chassis serves as a cooling device for an EI core. I've also seen cases where a manufacturer has used thermal compound from the core to chassis. Yamaha has also done this with specially made toroids in the P-2200 (for an example).
I don't dislike toroids as much as I have a problem with assigning them to much credit. Also, a transformer with lower high frequency response is a positive. Many transformers were rated for 60 Hz service (some 50Hz and 60Hz), but certainly not 400Hz. Anything that reduces high frequency noise from entering the power supply is a plus. Electrostatic shielding was developed for the same reason, different mechanism. You really do not want wide frequency response in a power transformer to the best of my knowledge.
-Chris
I am in the service industry, so I see complaints from a wide range of customers and equipment. I also understand the technical aspects of each transformer type.
My own opinion is that each type of transformer has it's strengths, but recently (for a few years now) the toroid transformer has been touted as the perfect part for a mains transformer. This is not always true, and there are cases where an EI part is superior. I just have a problem with everyone blindly recommending toroids.
If you look at the construction of an EI type, you will notice that there are two gaps in each magnetic circuit. These gaps are substantial when compared to a gapless toroid transformer.
I haven't researched this, but I'll bet the core of an EI type runs cooler than a toroid as well due to the accessibility of the core itself. It is known that the chassis serves as a cooling device for an EI core. I've also seen cases where a manufacturer has used thermal compound from the core to chassis. Yamaha has also done this with specially made toroids in the P-2200 (for an example).
I don't dislike toroids as much as I have a problem with assigning them to much credit. Also, a transformer with lower high frequency response is a positive. Many transformers were rated for 60 Hz service (some 50Hz and 60Hz), but certainly not 400Hz. Anything that reduces high frequency noise from entering the power supply is a plus. Electrostatic shielding was developed for the same reason, different mechanism. You really do not want wide frequency response in a power transformer to the best of my knowledge.
-Chris
DC on the AC supply
We all agree that there should be no DC on the AC supply, however I measure about 1.5->2V on my supply.
Since I am the only one on my pole transformer the DC on my supply must come from my house.
After a little investigation it appears to come from the heat / cool system.
Since DC on the supply is something we all have to live with I just deal with it.
Brian
We all agree that there should be no DC on the AC supply, however I measure about 1.5->2V on my supply.
Since I am the only one on my pole transformer the DC on my supply must come from my house.
After a little investigation it appears to come from the heat / cool system.
Since DC on the supply is something we all have to live with I just deal with it.
Brian
Let's not forget that toroids are considerably lighter... when you plan on production, freight costs have a lot to do with weight...
As for transformers often being designed 'to the edge' - to get the most out of a core. So, hang a resistive load off the transformer secondary and all is fine, but a rectifier is alltogether different.
As for transformers often being designed 'to the edge' - to get the most out of a core. So, hang a resistive load off the transformer secondary and all is fine, but a rectifier is alltogether different.
rlg_200 said:yeah!
toroid transformer is expensive if u buy in the manufacturer. however if u make on ur own u can less at 50%. I have toroid transformer for my own design and I used it for my sub amp. and my toroid transformer is works cool. thats why I like toriod.
rlg
where can i get info about how wire an toroid? i want to make my own transformer too
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