Has anyone tried any Double C-core transformers? (4a SS amp kit)

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gonefishin

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Joined 2003
#1
I've searched thru several sites (and google), but can't seem to find many people who have actually tried various Double C-core transformers in their SS amps. If anyone has any experience with any double C-core brand...or a couple brands...I'd love to hear your thoughts.

Also, being new to this SS state of affairs. The (lowered voltage) AKSA 55 amp has peaked my interest. This will be the amp I'm looking to use the Double C-cores on (80VA / AC secondary of 18-0-18V).

All suggestions/comments welcome!

thank you 😀
dan
 
#5
fdegrove said:

Double C and EI core xformers can have alot of advantages over toroidal powerxformers escpecially in this age of RFI pollution.
Click to expand...

Frank, I know the EI trafos couple less RFI than toroids, but
I just got an idea. Here in Sweden it is possible to buy EI
kits at decent prices, where the primary is wound and you
wind the secondary/ies yourself. They look as in the attached
picture.

Given that there are two bobins arranged as shown, would
a metal plate between the bobins serve as an electrostatic
shield (connected to a suitable ground point, of course)?
Unfortunately, the bobin seem to be double but come
in one single piece, yet I guess one could attach such a
shield on the secondry bobin if making it in two pieces.

These kits come decently priced by the way. A 420VA is
around 40 Euro and also has the advantage that you can
tailor the voltages and number of secondaries to your own
needs.

One more question to you all, is the thing you call a double
C-core the same thing as is often called an R-core?
 

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#6
Hi,

Christer, the dual bobbin designs normally do not require extra electrostatic shielding as the design itself already provides for excellent reduction of capacitive coupling between primary and secondary (-ies).

You can find those DIY kits at most suppliers through Western Europe BTW.

C-core, most often double c-core are mostly used for outputxformers and consist of what looks like the cores of two toroids cut in half (hence the C), the windings wrapped around the halves and than brought together again with a metal tier.

R-core look more like an eliptical, rectangular shaped toroid and is similar in construction to the C-cores, neither of wich are laminated. The R-core is mostly popular for its high effeciency as a powertransformer (SMPS) and normally not used for OPT duty although I do know of at least one company that makes those specifically for audio.

Cheers,😉
 
#10
fdegrove said:

Christer, the dual bobbin designs normally do not require extra electrostatic shielding as the design itself already provides for excellent reduction of capacitive coupling between primary and secondary (-ies).
(/QUOTE]

Thanks for the prompt answer. So I understand you then that
it would be overkill to add a shield for those trafos. Well, on
second thought that sounds reasonable.


C-core, most often double c-core are mostly used for outputxformers and consist of what looks like the cores of two toroids cut in half (hence the C), the windings wrapped around the halves and than brought together again with a metal tier.

R-core look more like an eliptical, rectangular shaped toroid and is similar in construction to the C-cores, neither of wich are laminated. The R-core is mostly popular for its high effeciency as a powertransformer (SMPS) and normally not used for OPT duty although I do know of at least one company that makes those specifically for audio.
Click to expand...

Maybe I misunderstand you, but I get the impression they
are basically the same thing, but the double C-core is circular
and the R-core elliptical (I know what the latter looks like and
the are used as mains transformers at leasst in some japanes
equipment, as I undeerstand mainly for their low capacitive
coupling). I think, BTW, the original question was regarding
mains tranformers, not OPT one, which is also what I am
interested in. Anyway, thanks for clearing things up.
Click to expand...
 
#11
grataku said:
No Christer it woudn't work.
Click to expand...

Could you elaborate on why? I understand from Franks answer
that it wouldn't be necessary anyway, but I'm still curious why
it wouldn't work? I am of course referring to a shiel between
primary and secondary bobins, not between the secondary
windings, but I guess that was obvious.
 
#12
Yeah, that's what I use it for. It makes excellent isolation for my system, no more need for a magic box on the cable wire and a lot of noise from the power is lost in that transformer.

Another thing I use it for is as a power supply transformer in a test amplifier I designed. It would be nice to get another transformer like this so I can leave one in the amp and use the other for power filtering.
 
#13
Hi,

I think, BTW, the original question was regarding mains tranformers, not OPT one, which is also what I am interested in. Anyway, thanks for clearing things up.
Click to expand...

Sure, I know it's about mains xformers but as the R-core is the more efficient of the two the double C is mostly used for OPTs of high quality as the cutting of the amorphous cores allows for tight matching between core halves and windings, this is important there but of little influence for powerxformers.

Cheers,😉
 
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