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Old 17th December 2002, 06:17 AM   #1
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Default Reactive Load Tests?

I'm looking for the best way to load a new amplifier tester I'm building. In the past, I've used simple high wattage resistors for basic power output (zero phase angle), but I'm getting more sophisticated and need reactive loads for more accurate stability tests. I'm not necessarily looking for a speaker-simulated impedance curve, but a set phase angle change.

I found something similar to what I would like to do at the Audiograph PowerCube site:

8 ohm +60, +30, 0, -30, -60 degrees +/- 5%
4 ohm +60, +30, 0, -30, -60 degrees +/- 5%
2 ohm +60, +30, 0, -30, -60 degrees +/- 5%

Any hard and fast rules for making this happen? The tester will be designed to handle ~600W RMS per channel. Hand winding inductors is not out of the question.

Thanks All!
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Old 17th December 2002, 04:43 PM   #2
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At what frequency?
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Old 17th December 2002, 05:30 PM   #3
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Oh yeah...

I believe the standard IHF-A202 test is 400Hz.
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Old 23rd November 2011, 02:16 PM   #4
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So, has anyone built a DIY version of Audiograph's Powercube?
AudioGraph Power Cube - Stand Alone System

What's inside that box anyway?
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Old 23rd November 2011, 04:14 PM   #5
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regards Andrew T.
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Old 23rd November 2011, 04:54 PM   #6
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Old 23rd November 2011, 05:18 PM   #7
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Originally Posted by dirkwright View Post
So, has anyone built a DIY version of Audiograph's Powercube?
AudioGraph Power Cube - Stand Alone System

What's inside that box anyway?
Wow. That looks like the kind of box I sent Jon Risch a block diagram of back on 3/26/2007 via my g-mail account. Luckily, I kept that e-mail on record..

This is the block diagram. By altering the gain of the control side, you can simulate different resistances. By altering the sine/cos feed to the control load, you can change the impedance parameters you desire.

The way it works, if you want 8 ohms and the load is 8 ohms, the control out is zero. If you wish 4 ohms, drive the control side at a gain of -1, that makes the middle of the 8 ohm load remain at zero volts...the higher you make the control gain, the zero point of the load resistor will move closer to the amp under test, it will look like a lower resistor.

The phase angle works the same way, but just by altering the sine/cos mix.

Cheers, jn
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File Type: jpg basic amp test diagram[1].jpg (112.6 KB, 138 views)

Last edited by jneutron; 23rd November 2011 at 05:21 PM.
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Old 23rd November 2011, 05:43 PM   #8
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Thanks. I don't think Audoiograph does that, since they have a liquid cooled version... on a cart in a big box of course...

Have you built something like this?
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Old 23rd November 2011, 06:02 PM   #9
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Originally Posted by dirkwright View Post
Thanks. I don't think Audoiograph does that, since they have a liquid cooled version... on a cart in a big box of course...

Have you built something like this?
Yes. Back in '86 IIRC.

Mine had modifications to present as a constant resistor load, a constant voltage, or a constant power. I used a swtpc as the control amp. I never tried the phase aspect however.

Why would liquid cooled be different?

Cheers, jn
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Old 23rd November 2011, 06:20 PM   #10
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Originally Posted by jneutron View Post
Yes. Back in '86 IIRC.

Mine had modifications to present as a constant resistor load, a constant voltage, or a constant power. I used a swtpc as the control amp. I never tried the phase aspect however.

Why would liquid cooled be different?

Cheers, jn
So, we'd need a pretty powerful control amp then?

From what I can see from their website, the stand alone Power Cube has a bunch of electronics in it, whereas I think the Load Box is a set of passive components in a box with many switches. I think the load box would be an easier thing to build.

I just thought that the liquid cooled version was funny... like liquid cooled computers and amplifiers.

Last edited by dirkwright; 23rd November 2011 at 06:30 PM.
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