QA401 Audio Analyzer
The QA401 is our second generation of audio analyzers. The QA400 was its predecessor, which made serious inroads into the market in terms of price and performance.
The QA401 adds full isolation, making measurements of advanced amplifier topologies a snap. Differential inputs and outputs were also added, as was a switchable 20 dB attenuator.
All of these make the QA401 an ideal instrument for measuring high power amplifiers directly. The QA401’s input stage overload detection is wicked fast, powered purely by gates—no software. The QA401 input is rated to 56.4Vpp with the 20 dB attenuator active. We’ve tested the input with the attenuator OFF using a variac set for 25Vrms (70.5Vpp) and are pleased to report the fault could be sustained indefinitely.
The front panel also lets you know when the attenuator is active, giving you additional piece of mind just before you connect to the monster amp you’ve been working on.
The QA400 achieved a level of performance that bested just about any sound card out there. The QA401 takes that to the next level, beating the QA400 by 4-8 dB in most measurements.
And unlike a sound card, where you are dependent on the setting of the gain pot for your absolute measurements, the QA401 front end relies on precise 0.1% resistors to ensure impressive accuracy without any calibration. No volume knobs to worry about. No re-calibration at each measurement session. The measurement you made last month can be quickly repeated tomorrow without any tuning or tweaking.
The input stage to the AK5397 ADC consists of a relay attenuator, an OPA1612 buffer, and an OPA1632 diff amp--premium components that lead in their respective categories.
The QA401 bypasses the Windows Audio Subsystem to ensure that your measurements aren’t clouded by a third party app changing gain settings. This is important to understand, because it means you aren’t able to use just any software with the QA400 and QA401.
The QA401 software has been evolved from the QA400 software to better cope with the higher resolution converters. For example, the entire signal path was converted from floating point to double precision.
The FIFO depths in the FPGA have been expanded, ensuring we can improve functionality, as we have with the QA400, well into the future.
Programmability has been a key driver in all of our products. Instead of communicating across antiquated interfaces with non-type-safe languages, our products and interfaces take advantage of modern type-safe languages, making it easy for you to write high performance interfaces that communicate to a device on your desk or across the world.
Click on the link below for detailed specs and performance reports on the QA401
- DIYAudio Thread on the QA400/QA401
- QA40x and IMD Measurements
- Evaluating Class D Amps with the QA401
- Swept Measurements
- ASIO and Hypermiling THD