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Author Topic: Best way to do a transfer function of an amplifier output?  (Read 309 times)

John Penkala

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Best way to do a transfer function of an amplifier output?
« on: June 18, 2018, 02:29:40 pm »

I'd like to do a transfer function of an amplifiers output to "see the processing". How are folks padding down the output of the amplifier to a level that a USB I/O can handle? Any help is appreciated.

JP
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Nathan Riddle

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Re: Best way to do a transfer function of an amplifier output?
« Reply #1 on: June 18, 2018, 02:46:15 pm »

You can connect it directly, just don't exceed 24v or so (for an interface with line level inputs) :P

(I've done it, just be careful of the gain knob ;) )

Any *nearly voltage divider will work though.
http://www.epanorama.net/circuits/speaker_to_line.html/

If you really don't want to blow up your equipment then isolated transformer is best way to go.

If you want to run the amp (depends on max voltage) into clipping then you'd need higher value resistors and wattage.

good luck have fun!
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Ivan Beaver

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Re: Best way to do a transfer function of an amplifier output?
« Reply #2 on: June 23, 2018, 02:09:55 pm »

I built a box that has a pad on the amplifier output, then that goes into an old Altec line level transformer.

The main reason for the transformer is to provide physical isolation between the amp and the interface input.

This way you can look at bridged outputs, or amps that have both output terminals floating.

Be sure to use a high quality transformer to avoid saturation.

The pad size will depend on the size of the amp being looked at.  But if you calculate it to get to around a -10dBu or so, the transformer should be fine.

Or you can simply turn the amp down.

It all depends on exactly what you are trying to measure and why.

BTW I use this method when setting up/matching transfer functions of amps with DSPs in them.
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David Sturzenbecher

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Re: Best way to do a transfer function of an amplifier output?
« Reply #3 on: June 23, 2018, 03:43:09 pm »

I have always used the VIbox from linearX in the past with great success. Unfortunately they are no longer available due to the passing of the companies owner.


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