Has anyone used an "ARTA Style" Voltage probe with REW?

[David Eisan]

Hello,

The title pretty much says it all,

Has anyone used and ARTA Style Voltage probe with REW?

 

[Antonio Di Motta]

Yes I always use this configuration since, in general, the line input of the sound card accepts signals up to a maximum of 1veff while the acoustic measurements are normally
carried out with a speaker voltage of 2.83Veff equal to 1W out of 8 ohms and therefore it is absolutely necessary to attenuate the signal through the divider R1 R2.
As far as the output capacity is concerned, this protection is not absolutely necessary, in fact if we use an amplifier with single power supply this capacity is already included in the
amplifier while if we have a dual power amplifier no capacity is needed.

 

[Antonio Di Motta]

If we measure the response of a driver for high frequencies it is absolutely useless to carry out the measurement starting from 20Hz, just set the sweep to 500Hz and we do not risk improperly stressing the driver. No protection capacitor is also needed because it would alter the response by making an unwanted cut of frequency.

 

[Antonio Di Motta]

If the measurement is made at 2.83Veff at the amplifier output, it is not necessary to insert the two protection zener diodes, since the signal will always be lower than the maximum input level of the sound card. In the proposed configuration with the 8,2Kohm and 910 ohm divider, the attenuation introduced is 20db therefore the input signal to the sound card is 1/10 xVout_amplifier, that is 283mV.
In this configuration, to reach 1 Veff at the input of the sound card we must reach the output level of the amplifier at 10veff equal to 12.5W.