EI core versus C-core Output Transformer
There’s always this perception that C-core or double C-core output
transformers are far more superior to the standard EI core output transformers.
C-core transformer versus EI core transformer |
Well, it is true to some extent that C-core has lesser stray
flux compared to EI core, and therefore lost is smaller, and impact to the
surrounding is also lesser in comparison. The core itself will radiate stray
flux, especially with the 90 degC sharp corners that the EI has, more is
radiated compared to the rounded edge of the C-core transformer.
For EI core, the section where the cores are connected
inevitably will have minor gap and therefore there will be stray flux radiated
from there. For C-core, the section is smaller, and it is usually covered by
the bobbin + windings, and therefore stray flux is lesser comparatively.
One reason limiting the popularity of C-core is the
flexibility of size. Usually the C-cores are predetermined in size and therefore
to customize it according to applications will be difficult, resulting in
wastage due oversize core. Users cannot stack more laminations to the core to
increase the capacity. This is something equipment manufacturers do not like.
There are also several other reasons too that involves materials and
manufacturing difficulties and costs but it will not be covered here.
If the EI core winder has enough experience, know-how and
expertise to wind a good EI core transformer, the cost / performance ratio can
match such that of a C-core transformer. The winder just needs to address the
shortcomings of the EI core transformer and apply remedies to resolve it. With
the flexibility to adjust the EI core size (capacity), it brings a lot of
benefit for fine tuning the size requirement of the transformer.
So, don’t be too superstitious. EI core or C-core are all
usable and can sound pretty good. What matters is where you get it from,
whether it is wound by an amateur or a true professional that demands for
quality and reliability, with the right partnering components like the magnet
wire, insulation material, winding
technique, insulation technique, output taps drawing methodology and etc.
Just like what HIFI guru always says, design is far more
important than material. You can have a so-so material, but with the right
design and application, it will still be a good match. With better material, it
would be better! If you have the best material, but with the wrong design, it’s
worse that what’s mentioned above.
J&K Audio Design
19/12/2013
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Click here to find out what output transformers we have.
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