Best (C core?) transformers for passive monitor controller

Saxtrack · 3rd September 2007

Hi,

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?

Thanks

Saxtrack

nosebleedaudio · 3rd September 2007

Jensen JT-11-BMCF, is their best 600 to 600 ohm.

Saxtrack · 4th September 2007

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

Any other suggestions?

tINY · 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?

-tINY

Saxtrack · 4th September 2007

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.

tINY · 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.

-tINY

3rd September 2007	#1
Saxtrack Gear Head Join Date: Oct 2005 Posts: 56 Thread Starter	Best (C core?) transformers for passive monitor controller Hi, 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? Thanks Saxtrack

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3rd September 2007	#2
nosebleedaudio Lives for gear Join Date: Jun 2005 Location: Birmingham, AL USA Posts: 3,547	Jensen JT-11-BMCF, is their best 600 to 600 ohm.

4th September 2007	#3
Saxtrack Gear Head Join Date: Oct 2005 Posts: 56 Thread Starter	Thanks. Do you know if the Jensen uses a C core? Any other suggestions?

4th September 2007	#4
tINY Gear Guru Join Date: Jul 2004 Location: Orygun Posts: 10,206	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? -tINY

5th September 2007	#6
tINY Gear Guru Join Date: Jul 2004 Location: Orygun Posts: 10,206	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. -tINY