Hi,
I just joined this forum. Great forum, and very helpful people, including Mr Pass himself! I am planning on my first (from scratch) diy project, a pair of aleph 3 monos.
While researching for power transformers, I came across the article http://www.soundstage.com/maxdb/maxdb071998.htm
This article makes the case for using EI core transformers for better audio. Curious about your opinions on this subject.
I am getting the PCBs from Kristijan. The power supply that Kristijan suggests has a 2 x 21v 200VA transformer. I could only find a 2 x 18v 175VA EI core transformers. So, custom wound is my only option? I couldn't find any toroids neither with that specs. The aleph 3 service manual doesn't specify the specs for the transformer, but the rails are 25v. Please help me in finding a transformer.
Thanks for any help,
pcn
I just joined this forum. Great forum, and very helpful people, including Mr Pass himself! I am planning on my first (from scratch) diy project, a pair of aleph 3 monos.
While researching for power transformers, I came across the article http://www.soundstage.com/maxdb/maxdb071998.htm
This article makes the case for using EI core transformers for better audio. Curious about your opinions on this subject.
I am getting the PCBs from Kristijan. The power supply that Kristijan suggests has a 2 x 21v 200VA transformer. I could only find a 2 x 18v 175VA EI core transformers. So, custom wound is my only option? I couldn't find any toroids neither with that specs. The aleph 3 service manual doesn't specify the specs for the transformer, but the rails are 25v. Please help me in finding a transformer.
Thanks for any help,
pcn
There's also Toroid corp of Maryland:
http://toroid.com
I like their kits which supplies you with a pre-made primary which you wind on whatever secondaries you want. The kit comes wiht a design guide and a final wrap. You supply the magnet wire for the secondary. Not real useful for standard types of transformers like the aleph units you want, but if you have a need for a lot of windings or odd voltages, they are handy.
Sheldon
http://toroid.com
I like their kits which supplies you with a pre-made primary which you wind on whatever secondaries you want. The kit comes wiht a design guide and a final wrap. You supply the magnet wire for the secondary. Not real useful for standard types of transformers like the aleph units you want, but if you have a need for a lot of windings or odd voltages, they are handy.
Sheldon
yeah, just checking the toroid.com website for their kits, very VERY useless when it comes to standard toroids .. $72 for a 400VA model???
i got a 400VA model for like $55 already wound for 2 secondaries
of course, if you do need odd secondary voltages, and odd # of transformers, then its a good deal
i got a 400VA model for like $55 already wound for 2 secondaries
of course, if you do need odd secondary voltages, and odd # of transformers, then its a good deal
The article doesn't make mention of another factor which is relevant in todays High-End systems: AC Filtering.
Although I can't recall details, I remember reading an article about the frequency responses of EI ve Toroidal AC power transformers, and it concluded that EI's were better as they had a vastly lower frequency response to EMI and 'hash' and thus acted as better AC line filters than Toroidals.
Although I can't recall details, I remember reading an article about the frequency responses of EI ve Toroidal AC power transformers, and it concluded that EI's were better as they had a vastly lower frequency response to EMI and 'hash' and thus acted as better AC line filters than Toroidals.
Sound good but....
I read the article regarding the benefits of EI core transformers and thought, hmmm, nice attempt at explaining why some manufacturers use cheaper transformers. Great smoke and mirrors job!
Look out here comes the caveat; I'm not infallible but I do have both electrical and electronic engineering qualifications and 25 years audio experience.
The article reminded me of a very scientific paper that described the grain orientation of copper wire used for speaker cables. It stated that because the copper was DRAWN, (stretched through a die to make it the required thickness) in one direction the grains are directional and the electrons travel easier in this direction. Sounds good but 2 minor flaws, (read bloody great flaws!) The wire is drawn in both directions during manufacture and sound is carried by AC, electrons flowing in both directions equally!
OK, so back to the transformers, DC offset in AC power supplies is very very small and effects BOTH EI and toroidal transformers the same, they do not saturate the cores of transformers unless;
1. There is something VERY wrong with your supply and if there is expect some of your equipment to over heat and burnout.
2. The transformer has been made without enough core material, (read cheap) and that applies to both styles of manufacture!
I haven’t heard everything on the subject I’m sure, but I’ve yet to hear a good reason to use EI core transformers in preference to toroids except COST. I’d love to go on further but I’ve got a life to live and music to listen to.
So enjoy the music, both transformers work well, (usual ceveats),
Walker
I read the article regarding the benefits of EI core transformers and thought, hmmm, nice attempt at explaining why some manufacturers use cheaper transformers. Great smoke and mirrors job!
Look out here comes the caveat; I'm not infallible but I do have both electrical and electronic engineering qualifications and 25 years audio experience.
The article reminded me of a very scientific paper that described the grain orientation of copper wire used for speaker cables. It stated that because the copper was DRAWN, (stretched through a die to make it the required thickness) in one direction the grains are directional and the electrons travel easier in this direction. Sounds good but 2 minor flaws, (read bloody great flaws!) The wire is drawn in both directions during manufacture and sound is carried by AC, electrons flowing in both directions equally!
OK, so back to the transformers, DC offset in AC power supplies is very very small and effects BOTH EI and toroidal transformers the same, they do not saturate the cores of transformers unless;
1. There is something VERY wrong with your supply and if there is expect some of your equipment to over heat and burnout.
2. The transformer has been made without enough core material, (read cheap) and that applies to both styles of manufacture!
I haven’t heard everything on the subject I’m sure, but I’ve yet to hear a good reason to use EI core transformers in preference to toroids except COST. I’d love to go on further but I’ve got a life to live and music to listen to.
So enjoy the music, both transformers work well, (usual ceveats),
Walker
To answer your question about transformers, I will quote interview with John Curl, a designer behind Mark Levinson JC-2 and Vendetta preamplifier:
"When we talk about transformers we have to separate power amps and preamps. While they are not perfect, Toroidal transformers are logical choice for power amplifiers because they are very efficient, they tend to have a fairly low hum field, and they're readily available in large power ratings.
For preamplifiers and other line-level components, the old type EI transformers or what's called a D-core or split C-core transformer is actually better than a toroid. First of all, they tend to be more compact, and second, and perhaps more importantly, they have very low capacitance between the windings.
This can be a problem when Toroids are used in low level signal applications; the windings are on top of each other so they talk to each other. And today the AC power is so dirty. We fix that by using a transformer that isolates the winding, which is important on low level circuits. The old style EI or the new C- or D-core is the ultimate in that respect-as long as it is a dual-bobbin winding with physically separate bobbins for the primary and for secondary. It makes big difference in sound quality."
I'm only using split bobbin transformers for line level equipment now, never had problem with buzzing.
"When we talk about transformers we have to separate power amps and preamps. While they are not perfect, Toroidal transformers are logical choice for power amplifiers because they are very efficient, they tend to have a fairly low hum field, and they're readily available in large power ratings.
For preamplifiers and other line-level components, the old type EI transformers or what's called a D-core or split C-core transformer is actually better than a toroid. First of all, they tend to be more compact, and second, and perhaps more importantly, they have very low capacitance between the windings.
This can be a problem when Toroids are used in low level signal applications; the windings are on top of each other so they talk to each other. And today the AC power is so dirty. We fix that by using a transformer that isolates the winding, which is important on low level circuits. The old style EI or the new C- or D-core is the ultimate in that respect-as long as it is a dual-bobbin winding with physically separate bobbins for the primary and for secondary. It makes big difference in sound quality."
I'm only using split bobbin transformers for line level equipment now, never had problem with buzzing.
Can't argue with subjective posts
Can't argue with subjective posts, but that doesn't mean that they're wrong!
jh6you, your experiences are interesting, have you been able to evaluate the same amp designs with different transformers? Some thing I'll have to try some time.
EI for preamps, hmmm, I don't see that input filtering is the job of the transformer, just a benefit and EI's fix the noise problem by introducing another, as do dual bobbin transformers. A Faraday shield, (electrostatic shield), easily takes care of Capacitive coupling between primary and secondary windings. Both transformer constructions can have them included but I have to admit that I've seen more fitted to IE transformers than toroids. Again cost raises its ugly head.
If you have a noisy AC supply, fix it, don't expect the transformer to remove the symptoms. AC supply filtering isn't a black art, though at times it appears to be
I still think that toroids are better transformers, all be it at a higher price, but I've been wrong before, and will be again
Both transformer constructions still do a great job, enjoy the music, take care, regards WALKER!
Can't argue with subjective posts, but that doesn't mean that they're wrong!
jh6you, your experiences are interesting, have you been able to evaluate the same amp designs with different transformers? Some thing I'll have to try some time.
EI for preamps, hmmm, I don't see that input filtering is the job of the transformer, just a benefit and EI's fix the noise problem by introducing another, as do dual bobbin transformers. A Faraday shield, (electrostatic shield), easily takes care of Capacitive coupling between primary and secondary windings. Both transformer constructions can have them included but I have to admit that I've seen more fitted to IE transformers than toroids. Again cost raises its ugly head.
If you have a noisy AC supply, fix it, don't expect the transformer to remove the symptoms. AC supply filtering isn't a black art, though at times it appears to be
I still think that toroids are better transformers, all be it at a higher price, but I've been wrong before, and will be again
Both transformer constructions still do a great job, enjoy the music, take care, regards WALKER!
I was also biased to use EI as I was told that they are superior to toroids. So was for a big surprised when I built powr supply for my GC using two 200VA EI transformer with split bobbuns (one transformer per rail). It sounded worse than a PS using a single, 400VA Plitron toroid, everything else being equal. So now I will be listening firs before deciding on a transformer.
"A Faraday shield, (electrostatic shield), easily takes care of Capacitive coupling between primary and secondary windings."
Garbage repeated endlessly is still garbage.
A split-bobbin EI transformer has less capacitance than a toroid with an electrostatic shield.
I own a capacitance meter, do you?
"I still think that toroids are better transformers, all be it at a higher price, but I've been wrong before, and will be again"
In small quantities toroids cost less than EI types, one reason why they are popular.
"AC supply filtering isn't a black art, though at times it appears to be"
Maybe you should apply for the job of designing them. Most off-the-shelf line filters INCREASE the noise.
I have had people want to return power amps with toroids because of mechanical 'buzz' from the transfomer. I don't get that with EI types.
Put these on toroids all the time, never used one yet on an EI transformer:
http://www.hifi-notes.com/images/offsetkiller300i1.jpg
Garbage repeated endlessly is still garbage.
A split-bobbin EI transformer has less capacitance than a toroid with an electrostatic shield.
I own a capacitance meter, do you?
"I still think that toroids are better transformers, all be it at a higher price, but I've been wrong before, and will be again"
In small quantities toroids cost less than EI types, one reason why they are popular.
"AC supply filtering isn't a black art, though at times it appears to be"
Maybe you should apply for the job of designing them. Most off-the-shelf line filters INCREASE the noise.
I have had people want to return power amps with toroids because of mechanical 'buzz' from the transfomer. I don't get that with EI types.
Put these on toroids all the time, never used one yet on an EI transformer:
http://www.hifi-notes.com/images/offsetkiller300i1.jpg
Not sure I should touch this one.........
In brief, let's say in transformers, you only get what you pay for. I have many good and bad examples of either style.
I use both, and I can not give an easy, all-encompassing rule as to which and when. Sorry, it is not that easy. Sometimes factors other than performance dictate which is used. The trick is then to make whatever you end up with work.
I know........no help at all............
Jocko
In brief, let's say in transformers, you only get what you pay for. I have many good and bad examples of either style.
I use both, and I can not give an easy, all-encompassing rule as to which and when. Sorry, it is not that easy. Sometimes factors other than performance dictate which is used. The trick is then to make whatever you end up with work.
I know........no help at all............
Jocko
Djk, read your post with much mirth, cheers.
Lets not forget that the amount of capacitance isn't the important issue, its ability to pass noise through electrostatic coupling from primary to secondary windings seems to be the concern. With a faraday shield there is a lot of capacitance from primary to the shield and much the same between the secondary and shield. If the shield is connected to a quiet enough ground, then dV/dt (electrostatic) garbage in, garbage goes to ground. The secondary is electrostatically connected to ground not the primary. Please correct me if I’ve missed the point you were trying to make. Garbage in garbage out, is a little vague.
I still believe that "A Faraday shield, (electrostatic shield), easily takes care of Capacitive coupling between primary and secondary windings."
Djk, you’re not the first to buy an off the shelf filter and expected of it, what it wasn’t designed to do, been there myself in the murky past.
Regarding magnetostriction noise. I’m not even going to try to guess how many noisy transformers that I’ve come across or had to silence, but it’s got to be 3 figures at least. The majority of transformers are EI so it would be hard for me to accurately gauge which where more prone the magnetostriction noise. I have a humming EI here at the moment that I have to deal with, I’ll try the usual fixes and replace it if they don’t work. One common denominator with noisy transformers that I have noticed is the cheap ones tend to be the culprit more often, funny that.
Djk, I also have been able to buy toroids in the past occasionally cheaper than EI but they were I suspect surplus stock. If cost is the main driver here I think we all know the winner
The offset killer? A MOV? That won’t kill the offset, it will clip the waveform, the offset remains, but you’ve got to love the marketing
Dhaen, you are right in my experience, toroids with faraday shields are the exception and more costly, in fact EIs with shields are also a rare breed. I’ve only found them where noise is an issue that the manufacturer is prepared to deal with. If low cost and availability were a key issue then EIs without shields would be the obvious choice in most cases.
Tbla, I wish I could read Danish? So you’ve got me at a disadvantage, would you like to summarise the article?
Enjoy the music, take care, regards WALKER
Oh, and capacitance meters, yes I do own a few, 3 last count, but that doesn't mean I know anything other than where to but them
Lets not forget that the amount of capacitance isn't the important issue, its ability to pass noise through electrostatic coupling from primary to secondary windings seems to be the concern. With a faraday shield there is a lot of capacitance from primary to the shield and much the same between the secondary and shield. If the shield is connected to a quiet enough ground, then dV/dt (electrostatic) garbage in, garbage goes to ground. The secondary is electrostatically connected to ground not the primary. Please correct me if I’ve missed the point you were trying to make. Garbage in garbage out, is a little vague.
I still believe that "A Faraday shield, (electrostatic shield), easily takes care of Capacitive coupling between primary and secondary windings."
Djk, you’re not the first to buy an off the shelf filter and expected of it, what it wasn’t designed to do, been there myself in the murky past.
Regarding magnetostriction noise. I’m not even going to try to guess how many noisy transformers that I’ve come across or had to silence, but it’s got to be 3 figures at least. The majority of transformers are EI so it would be hard for me to accurately gauge which where more prone the magnetostriction noise. I have a humming EI here at the moment that I have to deal with, I’ll try the usual fixes and replace it if they don’t work. One common denominator with noisy transformers that I have noticed is the cheap ones tend to be the culprit more often, funny that.
Djk, I also have been able to buy toroids in the past occasionally cheaper than EI but they were I suspect surplus stock. If cost is the main driver here I think we all know the winner
The offset killer? A MOV? That won’t kill the offset, it will clip the waveform, the offset remains, but you’ve got to love the marketing
Dhaen, you are right in my experience, toroids with faraday shields are the exception and more costly, in fact EIs with shields are also a rare breed. I’ve only found them where noise is an issue that the manufacturer is prepared to deal with. If low cost and availability were a key issue then EIs without shields would be the obvious choice in most cases.
Tbla, I wish I could read Danish? So you’ve got me at a disadvantage, would you like to summarise the article?
Enjoy the music, take care, regards WALKER
Oh, and capacitance meters, yes I do own a few, 3 last count, but that doesn't mean I know anything other than where to but them
I'm confused 
Are you saying the big cap(s) in series with the transformer primary cannot or do not block DC from reaching the transformer?
mlloyd1
Are you saying the big cap(s) in series with the transformer primary cannot or do not block DC from reaching the transformer?
mlloyd1
walker said:....
The offset killer? A MOV? That won’t kill the offset, it will clip the waveform, the offset remains, but you’ve got to love the marketing
.....
This article makes one fundamental mistake: the assumption that different AC loading on the two phases of the secondary of your power distribution transformer results in DC. It does not.pcn said:
What causes DC is asymmetric rectification, which commonly occurs when some appliance is controlled by a Triac or attentuated with a diode.
Dc does cause noise in toroids, and is a pain in the butt for high end manufacturers, where absolute mechanical silence is required. The solution generally revolves around some form of filtering or DC current limiting. Companies like Plitron, which we use, design their primaries more conservatively and also pot the mechanical assembly better. A thermistor in series with the primary also helps, as does dual rectifiers on the secondary.
As to the difference in sound between EI and toroids? The toroids, properly used, win every time for higher power applications.
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