Introducing the QA480

I will purchase one, please.

Richard Marsh

Please let me know when you start selling the QA480. I’d like to get one too.

I would like to purchase one QA480 as well. Cheers.

Hi @CurtisIIX, please send a mail to sales with QA480 in the subject and you’ll get an emailed link when orders can be made.

I read through your notes on the QA480 and the effect of the shared supply. What would be the impact of separating the supplies and grounds of the oscillator and the notch filter? Based on some other products doing that you could make the oscillator function as a balanced or single ended source by alternately grounding or floating one output.
As for tuning the way Fluke handles that on some of the precision standards are extra resistors (they do not need to be .01%) and solder bridges.to alter the primary resistor value.
Needless to say I’m interested and will be following this.

That’s a good question. I think for now, in loopback, there probably wouldn’t be much difference now that the errant 2 kHz that was showing up in the notch is gone as that limited the performance. But, once you stick a really high-powered class D DUT in the loop, maybe it would help. Specifically, there are some really high performance class D amps with that are hitting -116 dB THDN and with 131 dB of dynamic range that could conceivably demonstrate the need for additional decoupling.

I wrote a short study on the differences between the common high power class D (such as TPA3255) and this next generation class D (Purifi 1ET400A) HERE. The study looks at noise floor. If there was a situation that might demonstrate the need for more isolation, it’d be that. That amp runs at a 500 kHz switching frequency, so the ~90 dB of attenuation the QA451 has at 500 kHz would help. But I don’t know if it would be enough. The plot below is the SPICE sim of the QA452 filter (from HERE).