Where can found R-core Transformer?

Elso:

May I assume that your application is for power transformers? (The characteristics that are appropriate for 50/60Hz power transformers are definitely not the same as what is recommended for wide-band signal transformers.)

Toroidal transformers have good regulation and low output impedance, but OTOH high interwinding capacitance. High interwinding capacitance means wide bandwidth coupling between the primary and secondary windings. This may not be what you want in an audio power supply, as it implies that all kinds of noise as well as 50/60Hz can pass through the power supply. A toroidal transformer intended for a power supply should have an additional electrostatic shield between the primary & secondary windings, as this helps reduce the primary-secondary noise transmission issue somewhat.

EI (frame) core and R-core transformers usually have split-bobbin primary and secondary windings, which cuts down on interwinding capacitance and makes it considerably more difficult for non-50/60Hz noise components to pass in and out of the power supply. Additionally, R-cores have low levels of radiated magnetic flux and mechanical vibration, which allows them to be positioned closer to sensitive aplification circuitry without causing problems.

FWIW, I have experienced much greater variation in quality with EI-core power transformers than R-cores. I can't recall any R-core power transformer that I have used as having caused problems, but while a good EI-core is also perfectly acceptable, some EI-core transformers have definite quality problems in the areas of hum and vibration, temperature rise, magnetic flux radiation, and so on. It pays to go with a good manufacturer.

With R-cores and EI cores, you can also specify additional electrostatic shielding between the primary & secondary windings for less noise transmission, but this is not as critical as it is when using a toroidal transformer for power supply applications.

Also, EI and R-cores are usually physically larger and heavier for a given VA rating (at a given flux) than a toroidal, and this can have a direct impact on the size and weight of the supporting chassis.

hth, jonathan carr
 
Its not shaped like an "R". the shape is somewhat / kind of/ somewhat like a rectangle but with rounded ends. The "R" stands for racecourse as in horse racing, that is what they use to describe the shape. If you go the link Planet 10 posted you will see them. I bought a pair of the single end RW-20's soon after they first came out.

AB
 
Hi,

What are the advantages, (from an users perspective) with using a R-core transformer compared to a C-core? For me they look very similar although I can understand that there are advantages from a mass production perspective i.e. no need to cut the core, polishing the ends and clamp the whole thing together.

Regards Hans
 
Andrewbee said:
Its not shaped like an "R". the shape is somewhat / kind of/ somewhat like a rectangle but with rounded ends. The "R" stands for racecourse as in horse racing, that is what they use to describe the shape. If you go the link Planet 10 posted you will see them. I bought a pair of the single end RW-20's soon after they first came out.

AB


Thanx AB. I always just assumed those were double C-cores, since you don't see what is in the middle where the wire is wound. No band clamp though. It never occured to me. I don't own any of these so I didn't have a hands on model to study.
 
Power Transformers

Hello Jonathan, I am aware of all that information in your post.
I compared a 30 Watt toroid from Amplimo with a dual chamber 30Watt from Era in my DAC and preamp, three years ago. The split bobbin is always giving better sound.
www.amplimo.nl
www.era.de
My interest in transformers is revived as I noted a substantial improvement in sound when I placed a second 30Watt transformer parallel to the original one. I am really puzzled by this result as my DAC does not draw very much current; I guess something like +/-250mA. I have 1 Ohm resistors in series with the secondaries as in Jim Hagerman's schematic for the bugle power supply.
http://www.hagtech.com/images/powersupply.gif
So before ordering a 330Watt EI-core I was curious how much difference a R-core would make.
I also noted a higher DC resistance in the secondary for a 50 Watt toroid from Sedlbauer compared with a 30 Watt dual chamber from Era.
:confused:
 
Advantages of R-core trannsformers

tubetvr said:
Hi,

What are the advantages, (from an users perspective) with using a R-core transformer compared to a C-core? For me they look very similar although I can understand that there are advantages from a mass production perspective i.e. no need to cut the core, polishing the ends and clamp the whole thing together.

Regards Hans
Hi Hans,
You can find the advantages here:
www.jeichicago.com/products/r-core.shtml
www.jeichicago.com/products/r-core_compare.shtml
But the question is what is the effect on the sound. :wave2:
 
>Hello Jonathan, I am aware of all that information in your post.<

In that case, Elso, why didn't you state what type of information that you looking for, instead of asking a horribly vague question that could be interpreted in half a dozen different ways?

As it is, writing a response to your question appears to have been a total waste of time. I will try not to make that mistake again in the future.

jonathan carr
 
Hi!

As for the comparison between a normal toroid and an R-Core, I can only say that I substituted a 300 VA 30 - 0 - 30 toroid for a 360 VA 33 - 0 - 33 and 36 - 0 - 36 R-core on a mono LC The End Millenium.
The 33 V, 330 VA windings driving the amp circuit, stabilized by 4 * 20.000 uF (63V) caps, and the 36 V, 30 VA windings driving the voltage amplifier and the driver stage, sabilized by 8 * 1000 uF (63V) caps.

In comparison, what is most evident is that there is no hum or vibration whatsoever (the cheap toroid was slightly humming and vibrating, only when you tourched it or put your ear near it).
Also there is no power-on thump (and I have no protection circuitry or resistors before the R-core).

If the sound is better, I can not really tell. But then I am also not able to tell the difference between a GC built with LM 3875, LM 3876, OPA 544, OPA 541 and OPA 549...

All I can say that the amp has enough power for my diy 15", 120l subwoofer which weights 67 kg...

I would say that an R-core should at least be considered for high end applications which do not need loads of power, like pre-amps or DACs... Which is exactly what for example Sony uses them for...


Bye,


Arndt