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Best (C core?) transformers for passive monitor controller
Old 3rd September 2007
Gear Head

Best (C core?) transformers for passive monitor controller


I would need advice which transformers would be great for a transformer volume control to be used with a passive monitor controller and/or as a hifi preamp.

Lundahl, Jensen?

Any suggestions here?

Which exact type of transformer would be suitable?


Old 3rd September 2007
Lives for gear
nosebleedaudio's Avatar

Jensen JT-11-BMCF, is their best 600 to 600 ohm.
Old 4th September 2007
Gear Head

Thanks. Do you know if the Jensen uses a C core?

Any other suggestions?
Old 4th September 2007

Do you mean a transformer volume control like a variac, where the transformer turns ratio is varable? If so, I am not aware of any.

If you want to use a transformer to isolate the input from the output, that's another story....

Why is it important what kind of core is used?


Old 4th September 2007
Gear Head

I mean a transformer coupled to a volume control to keep the output impedance
of a passive volume control stable. I read that C cores deliver superior audio quality.
Old 5th September 2007

I'm not sure how "stable" you'll keep the output impedance simply by using a transformer. Remember that impedances are reflected through the transformer by the square of the turns ratio (if I remember correctly).

So, the only way to "stabilize" anything is by having a pretty big step-up transformer (if I remember my theory right - it's late and I don't feel like checking).

Usually, a passive volume control is designed like an L-pad with a target input impedance for the device being driven into.


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