Thursday, February 1, 2024


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What is going on inside your audio equipment? We talk about frequency response, noise floor and dynamic range but where do these numbers come from? They come from the manufacturers of the equipment; but how do you know if these things are true?

QuantAsylum manufactures a range of affordable test equipment. The products are designed and built in the USA. 

The following comes directly from the QuantAsylum website:

QuantAsylum is a portmanteau of the words quantify (to measure) and asylum (protection, shelter, refuge). Since 2010, QuantAsylum has been developing and offering unique products for embedded hardware and software developers.”

I became aware of QA in the final quarter of 2023. I was looking into buying a much more expensive Audio Precision test system to do advanced performance analysis on audio equipment for High on Technology. Is the QA403 a replacement for a modern AudioPrecision system?

QA makes no pretense about their measurement capability which can be a little bit confusing as you digest the features of these little boxes. This product is aimed at industrial electronic engineers (NERDS) and unlike typical audio marketing, QA is not boasting or spewing a bunch of blah-blah-fluff: Instead, the company is delivering an extremely powerful audio testing device for an amazing low price. 

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It took me a couple of weeks of digging around the QuantAsylum website to realize what this little red box is really capable of; at that moment when it became clear I immediately placed an order for a QA403 Audio Analyzer. Honestly, it's so inexpensive, I had to build confidence it was something I wanted and needed. They were on backorder but it was not a horrible long wait and the time passed quickly. One awesome day near the end of November 2023 my QA403 arrived.

The QA403 gives you the capability of testing a complete, mono or stereo audio signal path, from input to output, balanced (differential) or unbalanced (single ended). You can benchmark characteristics like noise, distortion and frequency response easily after you understand how to make the necessary connections and operate the software on a Windows 10 based PC. 

Audio Analyzer Overview

The QA403 is part of a precision stereo audio test system. For a complete functioning system you need the QA403 hardware, the free software application from the QuantAsylum website and a Windows 10 based PC along with appropriate cables and terminators. 

Like all high quality analyzer systems the QA403 digitally generates “known” test signals; you feed these “known” signals from the generator into the input of a DUT (device under test), the output of the DUT is then connected back into the QA403 to test it for performance. 

For comparison, understanding and benchmarking you can check the quality of the QA403 by simply connecting the generator outputs back into the analyzer inputs and use the QA403 to check itself.

Inputs and Outputs

The QA403 has a precision stereo audio frequency generator which you feed into the “Device Under Test” (the gadget you're testing). The analog audio outputs from the QA403 generator section can be used balanced or unbalanced to accommodate all input/output configurations of consumer and professional audio equipment. 

The QA403 analyzer section has two pairs of differential inputs which can be used as one or two balanced or unbalanced input connections. In order to make accurate measurements you'll also need some inexpensive “input terminators” to mute any unused inputs on the analyzer which can skew the accuracy of measurements. Terminators with 75 or 50 ohm BNC connectors are cheap, half a dozen delivered from Amazon was under $10 and that quantity will get you going making measurements with the QA403.

All the audio inputs and outputs on the QA403 are BNC connectors. BNC connectors are those annoying weird cables you use to connect digital audio clocking signals on a DAW system. The BNC connectors on the QA403 provide 100% isolation and ground control when connecting devices to test. 

THE CONVERTERS - The converters in the QA403 are by ESS Technology. 

The Windows 10 PC Connection 

The QA403 is designed for a high speed (480Mbps) USB connection to a PC running Windows 10 or 11. The computer USB connection is completely isolated from the audio section of the analyzer so hash or noise from the computer won't distort your measurements. 

The current software version available through the QuantAsylum web site is a very compact package. There is no software key or licensing system, anyone can download the software but you need the QA403 to run it and have it make any sense. You can run the QA software from a USB memory stick if necessary. On my personal system I installed the software and it just worked. 

The QA403 is powered through the PC USB connection and it is a demanding load at 800mA. Many PC-USB outlets simply cannot handle the current draw. 

I bought a budget model AMD powered Lenovo laptop to use with the QA system. I added a 10-port powered USB hub which is capable of delivering 1,000mA to the QA403, I run the hub between the analyzer and the USB connection on the laptop; this allows the QA403 to get all the power it needs from the hub power supply and protects the PC USB connections from trying to draw too much current. 

Good Things In Tiny Packages

The QA403 is designed and built in the USA. The compact enclosure is aluminum, the paint and silkscreen nomenclature are very high quality. The QA403 features 24-bit ADC/DAC which can operate up to 192KSPS. The QA403 hardware inputs can handle +32 dBV in signal level which is equal to a little over 34dBu. That is over 7dBu louder than an SSL mixer screaming at the top of it's lungs so the QA403 is ready to handle some seriously big line-level professional signals. Even my vintage API 312 microphone preamps are out of gas at 30dBu of output level. The inputs on the QA403 have ample headroom to handle even the beefiest audio outputs in professional audio. 

Testing – Testing-Testing

Boutique equipment manufacturers are turning to QuantAsylum for affordable test gear to achieve high standards of reliability and quality control. A customized QA system including all cables and dedicated PC can be put together for under $1,000. The footprint for a system like this is small enough that the QA system can be right in the heart of manufacturing and easily integrated into the production process. 

For someone operating a recording facility the QA403 removes variables and provides several useful tests quickly and easily. The QA403 performs many additional tests through the use of programming. The ability to accurately perform just these four tests on a piece of studio gear can be the equivalent of a physical health check up. 




Frequency Response

If you're using a mixing console in your recording studio profiling the individual channels and the EQs with the QA403 can help you understand their impact on your recorded sound as well as finding channels that are performing poorly. A noisy switch can spray high frequency junk into your otherwise pristine mix. If you're using a pair of vacuum tube processors for stereo buss processing the QA403 can help you see the noise and frequency response of each so you achieve consistent stereo performance. 

Repair Shop Friend

The QA403 does not require calibration, that is done before the device leaves the factory and like your trusty DVM it is ready to answer the call with measurable, objective data. Typical handheld DVMs don't have good high frequency response to truly verify what the QA403 analyzer is telling you. A bench type meter with response out to 20K or beyond is recommended if you need that level of performance and verification. 

The QA403 Audio Analyzer is being used by repair shop techs and amp design engineers along with other boxes QA makes. The QA451 is a programmable 4 and 8 ohm load for amplifier testing. Check the QA website for detailed product information. QA makes a precision microphone preamp to accompany the other components which can be used in various audio industries (like In Ear Monitors).

Testing the actual full-range frequency response of your gear can be an eye opener and the QA403 makes frequency testing so easy and compact compared to setting up my dual-trace scope, calibrating my audio generator and testing the old way. 

I'm building a custom wood enclosure to hold and power the QA403 and USB hub, with room for the laptop on top. This will help integrate the components into a handy package I can move around the studio for doing tests with minimum cables blossoming out to catch on things. I'm also wanting to tidy up the AC power connection for powering the laptop and USB hub and make setup as quick and easy as possible.


I'm still just a noob with the QuantAsylum Audio Analyzer and not finished with the process of integrating my test rig for portable applications. I'll be doing A LOT more testing in the months ahead and you'll find it here on High on Technology. 

If you'd like to know more detailed information about the QA403 Audio Analyzer point your browser towards the QuantAsylum web site. You can download the “Users Manual” for the QA402/QA403 analyzers and dig in to see if one of these belongs in your tool box. 

Thanks for reading High On Technology, Good Music To You!

©Jan 2024 by Mark King, It's not ok to copy or quote without written permission.