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EI Transformers vs Toroidal Transformers

watchnerd

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Looking at high end Japanese analog integrated amps, I find it interesting the big stink each of the manufacturers makes in their marketing literature about the type of transformer they use, as opposed to just its rating.

Yamaha, as the very first feature in its marketing, touts its toroidal transformer:

"Toroidal Transformer
A large toroidal transformer has been used in the A-S3200 in the pursuit of pure musicality. With less flux leakage there is no negative impact on other sensitive audio circuits. Copper wire is directly drawn from the winded core, minimizing energy loss compared to other substitutes, allowing the full emotional energy in the music to be felt by the listener."

Luxman lists the power supply further down the page, but bothers to make a point that it uses an EI transformer:

"High stability power supply
The highly stable power supply circuit developed for the L-509X features a 600 VA EI-core-type power transformer and independent left and right channel large capacity blocking capacitors (10,000μFx4 per channel). This generous custom specification ensures that the power supply unit will not be affected by any load fluctuation."


Aside from the curiousity about why this transformer emphasis seems to be particularly Japanese, is there any meaningful reason to prefer one type vs the other, all things being equal?
 

sergeauckland

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Toroidal transformers have a much smaller external field, are physically smaller and lighter for the same rating, and have better regulation than EI laminated transformers. However, they are more expensive, and their benefits may not be significant in a large power amp where weight and size matters less and without a sensitive phono stage, so a hefty EI laminated transformer will do.

About the only benefit of an EI transformer I can think of is that their primary resistance is greater, and core bigger, so less bothered by DC on the mains, but otherwise A toroidal is better in every other respect save cost.

S
 

valerianf

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There is a simple advantage with the toroidal transformer: at equivalent volume, limited by the AVR enclosure, the available power is increased by 100%. If you want to have strong low frequency percusions that need high current look for a toroidal transformer.
Short story: I had a $60 amplifier that was driving my surround providing strong sound effects.
This amplifier died after some years and I bought the new one from the same manufacturer.
But the sound of the new one is dull.
The old amplifier had a toroidal transformer when the new one has an EI transformer!
The beans counter is the winner (EI technology is cheaper) and I am the looser.
Next I will try a class D amplifier.
 

Wombat

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Toroidal transformers became useful when low profile enclosures became popular. Either type can be suitably designed for purpose. Depending on design parameters and constraints either can be made to suit.

Toroidal transformers are somewhat less forgiving of DC in their primary winding.

Basic overview.
 
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dfuller

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E-I core parts have an advantage over toroidals in one unique way - they mount at multiple points. This is good for equipment that bets banged around a lot (see: guitar amps) because you have less chance of the transformer coming loose from a bolt shearing somehow.

Toroidals are more power-dense and generate less EMF but really don't like having DC on them which E-Is are more tolerant of.
 
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watchnerd

watchnerd

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Toroidal transformers have a much smaller external field, are physically smaller and lighter for the same rating, and have better regulation than EI laminated transformers. However, they are more expensive, and their benefits may not be significant in a large power amp where weight and size matters less and without a sensitive phono stage, so a hefty EI laminated transformer will do.

Thanks.

FWIW, in the above example, they both have phono stages.
 

sq225917

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Toroids for me, with a dc blocker in front of anything larger than 400va
 

ShadowFiend

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Both types of transformer have advantages & disadvantages.

1. Toroidal transformer generates much less stray magnetic field than EI-Core
2. EI Core has lower coupling capacitance between primary & secondary, so it blocks high frequency common mode noise from main AC far better than toroidal transformer
3. Toroidal transformer is susceptible for DC current from main, which cause hum sound.

If we only care about performances, EI Core is better at low wattage application like preamp/phono/DAC. Even though the stray magnetic field is stronger with EI-Core, at lower wattage application, the stray magnetic field is also pretty small, and can be blocked efficiently with shielding by transformer shield case made by iron and a sheet of mu-metal. Or even better, you can put the EI transformer to external power supply outside, and forget the stray magnetic field.

When manufacture cost is also in the equation, toroidal transformer is preferred as it enables smaller case design with low stray magnetic field.

Toroidal transformer is better at power amplifier. At the high current application, the stray magnetic field of EI-Core is too much that it can not be blocked effectively. And the external power supply is also not an option. The load current is too high, and causes a voltage drop in amplifier power supply, which does not have regulators to correct it.

My favorite transformer for power amplifier is R-Core, but high quality R-Core like Kitamura Kiden (Japan) is so expensive. The Indian R-Core is also very good.
 

FrantzM

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Toroidal transformers have to come to signify "High End" in the eyes of audiophiles of all persuasion. Any modern day High End Audio devices that needs to sell must feature a toroidal transforme, Same electrical performances could have been achieved with either, it is a matter of implementation as in most technical/technological endeavors.. As usual it is a bit more nuanced.
Read this thread on Audiogon..
https://forum.audiogon.com/discussions/toroidal-vs-non-toroidal-transformers

Peace
 
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watchnerd

watchnerd

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Toroidal transformers have to come to signify "High End" in the eyes of audiophiles of all persuasion. Any modern day High End Audio devices that needs to sell must feature a toroidal transforme,

Errrr....Luxman doesn't seem to have a problem selling and they're using EI transformers.
 

FrantzM

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A few exceptions. The overwhelming majority uses toroidal.
 
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watchnerd

watchnerd

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A few exceptions. The overwhelming majority uses toroidal.

I think most tube amps use EI transformers? Or at least some other non-toroidal kind.

MC1502-Transformers.ashx


Also, I'm pretty sure the McIntosh solid state amps don't use toroids, either.

MA8900-StereoNET2.ashx
 
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Panelhead

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I use both, and for a given power (voltage and current) rating EI are much more expensive than toroidal. The bandwidth of toroidal is higher, some more line noise couples through. The EI filter the line a little.
Normally buy the Antek toroidal due to pricing, availability, and size. And try to place in an external enclosure to minimize stray flux.
 
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watchnerd

watchnerd

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Toroidal is expensive so they work at max possible flux (they saturate easily by over voltage). With correct design EI lamination is better and easy to repair, and the core is naturally grounded. No real advantage for typical audio application.
http://www.soundstagenetwork.com/maxdb/maxdb071998.htm
I use both, and for a given power (voltage and current) rating EI are much more expensive than toroidal. The bandwidth of toroidal is higher, some more line noise couples through. The EI filter the line a little.
Normally buy the Antek toroidal due to pricing, availability, and size. And try to place in an external enclosure to minimize stray flux.

Okay, we have some people saying toroidal is more expensive and others saying EI is more expensive....
 

levimax

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EI transformers have much lower in rush current on start up so you dont need "soft start" circuits for large VA transformers which saves a lot of trouble especially for DIY. These "soft start" circuits all have some potential safety / reliability issues.
 

Doodski

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Power amps with a toroidal mains power supply have a lower output impedance.
 
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