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Old 3rd August 2012, 07:10 PM   #1
lpd is offline lpd  Canada
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Join Date: Nov 2003
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Default Interface Impedence

I have a pair of X's with a diy interface. Looks like Innersound transformer (single for step up) and Innersound bias. Impedance on the speaker input for the amp is .1 (dc), I'm assuming this is not good? Any way to modify, adjust ect to make load on the amp more friendly? I'm going to ground, fuse and make safer for starters. There isn't a treble or bass circuit, which I may have to add as well.

I have added a pic for reference....

http://i796.photobucket.com/albums/y...ping/Inner.jpg
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Old 4th August 2012, 07:47 AM   #2
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Location: Calgary on the Bow
if you are worried use some series resistance. what dis the original owner do? series R is a good idea to keep the transformer core from going into saturation look at Acoustat interface. Best regards Moray James.
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Old 4th August 2012, 07:55 AM   #3
lpd is offline lpd  Canada
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Quote:
Originally Posted by moray james View Post
if you are worried use some series resistance. what dis the original owner do? series R is a good idea to keep the transformer core from going into saturation look at Acoustat interface. Best regards Moray James.

Interface were designed by Roger Sanders. Here is details about them...


"The power supply is 4 kV with taps every 500 volts below that. The audio transformer has a turns ratio of 1:50, a frequency response of 40 Hz to 32 KHz, and will handle 10 kV.

There are no filters in the circuit as such passive components are unreliable and do not produce ideal frequency response characteristics. I use active circuits nowadays, primarily in the form of digital crossovers. These give much better results and make it possible to adjust every aspect of the speaker in real time. They are wonderful for DIY projects.

Transformers do not have an inherent impedance. The impedance of a transformer is determined by its load and turns ratio when measured using an AC signal.

You did not specify how you were measuring the impedance of the transformer or what load you used in the process. But if you measured the transformer without a load using a standard ohm meter, there will be no back EMF being produced and as a result, you will see an extremely low resistance, which is nothing more than the resistance of the wire. It would be normal to see about 1/3 ohm of resistance on the primary side of this transformer when using an ohm meter.

The secondary windings are wired in series and each has a DC resistance of about 75 ohms. So the pair should read approximately 150 ohms if you measure between the small blue and brown wires.

If you measure the impedance (using an AC signal), and you have the audio transformer connected to a capacitor of approximately 2 nF (a typical electrostatic speaker), the impedance will measure much higher due to the back EMF resisting the flow of current. The primary winding will show approximately 150 ohms @ 500 Hz and will fall linearly to about 1.3 ohms @ 20 KHz. This is normal for a capacitor since the impedance of a capacitor is inversely proportional to frequency.

Note that resistance applies to DC circuits (such as what you get with an ohm meter). Impedance is the same measurement as resistance, but applies to AC circuits and typically varies with frequency."


Plugged them into the Kyocera B-910 with fantastic results with steam to spare. I have two pairs so now I have to decide how to set up two sets of X's in one room.

Cheers and thank you.
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