Target Measurement Acquisition

I love my QA401 and I have just received my 402. I’m anxious to test it out and put it into place for my reviews.

One step that’s very time-consuming in testing amplifiers is to adjust the signal generator or amplifier sensitivity controls to reach a target measurement. For example, I take CTA-2006C-compliant S/N Ratio and THD measurements at 1 watt into 4 Ohms, so I work as hard as I can to set the output to 2.00 volts. Likewise, power measurements are taken at 1.0 THD+N - which requires more fine-tuning. I’m probably overly concerned with the accuracy, but I never want to be called-out for rushing my reviews.

I know the process would be difficult, but being able to have the software auto-set the signal generator to reach a target measurement or level would be amazing.

I agree that would be a useful feature. Tell the 402 that you want measurement with the input signal level increased to a point where the output power of the device is say 1w into 4 or 8 ohms, or maybe some other power level- probably not needed as much for newer devices but for older hardware, where frequency response may vary a dB or 2 or 3, it would be very nice.

Hi @Dave_MacKinnon, I think it should be pretty quick to hit exactly. Let’s say I want to hit 6 dBV DUT output from DUT precisely, and I’m using an DUT with unknown gain.

First, just ballpark levels to learn the gain of the amp.

Here I see the amp gain is 29.93 dB and the output (2.93 dBV) is far away from my target. So, if I want 6 dBV out of the amp, that’s 6 - 29.93 = -23.93 dBV. Put that into the generator and you should hit it dead on:

Be aware as the amp starts to go into compression (usually 1-2 dB away from it’s max) you’ll see the gain drop and the linearity go south really quickly. But in the linear region, the gain should be constant.