ARTA impedance measurements - help needed!!

[Svein_B]

zobsky, you seem to be using a SONIC IMPACT amplifier for your measurement setup.

As I understand, the T-amp and others chip-amps have "floating" speaker outputs, meaning that both the + and - speaker outputs are active (like a bridged amp). I suspect that this could be a potential source of your problems.

For testing I suggest:
- set your jig to Impedance Measurement mode (I consider the calibration switch unnecessary)
- do not connect a speaker
- Set level to get a couple of volt AC on the speaker terminals.
- Run calibration to check that you get equal signals to both channels (< 0.2 dB difference). Adjust balance if necessary.
- You may also use ARTA to run FR measurement on this set-up.


Svein B.

 

[zobsky]

zobsky, you seem to be using a SONIC IMPACT amplifier for your measurement setup.

As I understand, the T-amp and others chip-amps have "floating" speaker outputs, meaning that both the + and - speaker outputs are active (like a bridged amp). I suspect that this could be a potential source of your problems.

For testing I suggest:
- set your jig to Impedance Measurement mode (I consider the calibration switch unnecessary)
- do not connect a speaker
- Set level to get a couple of volt AC on the speaker terminals.
- Run calibration to check that you get equal signals to both channels (< 0.2 dB difference). Adjust balance if necessary.
- You may also use ARTA to run FR measurement on this set-up.


Svein B.

I'll try that. Without a driving amplifier, how would you suggest I get the line-out signal to the jig? Should I make something up to mate the jig's "amp-in" binding posts to the computer's "line-out"?

Thanks

 

[Svein_B]

I suggest you try a conventional amplifier, if you have one.
If your sound card has a speaker/headphone output that may also work.

I think the results with a balanced amplifier such as the T-amp, will be reduced impedance readings. When the load resistor equals the reference resistor I expect the result to indicate zero. Not sure what the result will be when the load is less than the reference.

SveinB.

 

[zobsky]

Just posting to thank everyone for their useful suggestions. In the end, the sound card line-out was enough to drive the speakers to obtain valid impedance curves. I had no issues using my panasonic mic capsule to obtain frequency measurements with ARA. Neat piece of software.

Thanks again.

End results:

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.