QuantAsylum Products

What's New: Recent Blog Posts

Using Notch Filters to Improve THD Measurements

by admin on Sunday, December 20, 2015 3:39 PM
The use of notch filters is a well-known technique for improving the THD measurement performance of audio and RF equipment. THD measurements are a challenge because you usually have a massive fundamental that you aren’t interested in, and several very small harmonics that you are interested in. But with a notch filter, you knock the fundamental down before it has a chance to interact with the non-linearity of the measuring equipment input stages. 

First, consider a discrete, low-distortion 1 KHz generator. There are many designs out there to chose from, and most are based on Wien-bridge topologies. Below we can see the output of the oscillator at 0 dBV going straight into the QA401. The THD is about –99 dB. More importantly, however, note that the 2nd harmonic is at 102 dB below the fundamental.



QA405 and QA401 Status

by admin on Sunday, November 01, 2015 9:45 PM
Note: Details below will be updated as required. All figures below are tentative until large batches of devices can be measured.

Last February 2015 we wrote about the QA405, which was to be the first successor to the QA400. It is bigger/strong/faster than the QA400 in every way. We noted at the time that the product was complex and expensive. Those are both still true.

However, we also asked for feedback from users, and feedback we got! Of course, there were some that wanted $10,000 tester performance for $200. But most understood that the next 5 or 10 dB of performance comes at increasing cost. People appreciated the convenience and repeatability of the QA400, but really wanted differential IO and isolation. Over and over those two items kept coming up.

In the post we noted we’d ship by the end of 2015. So, where are things today? We’re pleased to report we’ve made steady progress, albeit at somewhat of reduced scope. The evolved...

Visualizers and Examining the Residual

by admin on Sunday, June 28, 2015 10:01 AM
This post takes a look at a framework to enable you to write software that can perform custom analysis on captured waveforms, and display the results of that analysis, all within the application. This first release will focus on the QA400, and then we’ll add this same mechanism into an upcoming QA101/QA100 software release.

This will enable you to download visualizers from others to help with your data analysis needs. What could these do? These could be things to help analyze speaker parameters, room parameters, etc. But more importantly, the visualizers can display this information in a way that makes sense for the task at hand. Think of visualizers as domain-specific problem solvers.

Overview In a nutshell, a visualizer gives the plug-in writer a crack at the data to analyze it and and display it as needed. The core application works the same as it always has, but when a visualizer is doing its job, you’ll see an extra window opened. You can see this in the display below. There is an extra window...


by admin on Saturday, February 28, 2015 11:41 AM
We’ve had an ongoing background project which is best described as a QA400 on steroids. It features:

Modern ADCs and DACs Fully differential inputs with 1X, 0.1X and 0.01X gain settings AC or DC coupling on inputs Switchable 600 ohm or 100K ohm input impedance Fully differential output 10Vpp single-ended inputs/output, or 20Vpp differential High current headphone amp Switchable output impedance on headphone amp (1 ohm/50 ohm) Offset bias generation on headphone output (12-bit DAC spanning +/-10V gives ~5 mV resolution) Internal loopback switching Much larger audio buffer, which should permit ASIO support Up to 768Ksps/24 bit User-designed plug-in boards for the input signal path The above are subject to change, of course. The release date isn’t known at this point. The price will be several multiples over the QA400. And the QA400 will continue to exist for a long time. Both will run the exact same version of software.

The product is complex....

A Quick and Dirty Interpreter

by admin on Wednesday, November 05, 2014 8:53 PM
We had a need recently to verify the number of pulses in a data stream were correct. The pulses were driving a stepper motor, which added a bit of a twist because the stepper could jump from microstepping to full stepping once a certain speed had been reached. How could we be sure the precise number of pulses had been emitted by the FPGA? By using a custom interpreter, of course. It took about 15 minutes to modify an existing interpreter to do the trick.

Below you can see the output of the interpreter. The rules and code are very simple: Just count and display how many pulses are on the screen. In the case below, it’s easy to confirm the count is correct.



Why do I need a Mixed Signal Oscilloscope?

by admin on Thursday, May 29, 2014 7:58 PM
Introduction We get mails from people wondering how a mixed-signal oscilloscope differs from a regular oscilloscope, or perhaps wondering why an MSO is better than regular scope + a logic analyzer. And depending on the type of work you do, there might not be any difference. You might not need to look into the analog and digital realms at the same time. Some days you are studying why a switching supply isn’t working as expected, and then the next you are working on a SPI problem. And the two domains never intersect.

But for those that spend time working on complex mixed signal problems, a mixed signal scope lets you see things that you otherwise can’t see with separate tools because it shows you the analog and digital domains aligned in time. We recently found ourselves confronted with a problem that was not making sense and decided to write it up as a case study. We fixed the problem in the FGPA fairly quickly once we saw the bigger picture. It would have been nearly impossible to do so with just a logic...

Connecting to QuantAsylum Devices from C++

by admin on Saturday, March 22, 2014 11:10 AM

Generally, when we post articles on writing code to control your QuantAsylum hardware, the language of choice is C#. C# is a managed language, meaning there is an entity that is actively managing memory in the background. VisualBasic is also a managed language. C++ as offered by Microsoft has two flavors: Managed and unmanaged.

Managed C++ allows the developer to worry less about memory management if they want to. But more importantly, it fits into a larger framework Microsoft has built in which mirrors the framework available to C# and Visual Basic. This means the developer has access to rich run-time libraries that are very well thought out, sophisticated syntax for selecting data, and tool flows that all work the same. Overall, it allows the developer to reap all the benefits of a more modern language and infrastructure while still sticking with what they know.

Unmanaged C++ is how things have been done for the last 20 years, and there are countless apps written in (unmanaged)...

QuantAsylum Connection Manager

by admin on Saturday, March 15, 2014 11:42 AM
Controlling QuantAsylum products from code you have written is simple, and it’s about to get even easier if you are trying to control a device that resides on the same machine.  The previous way of doing things is still required if you are going to connect to your device over the internet. But most of the use cases our customers require don’t require a truly remote connection, and thus the shortcuts below should be helpful.

Architecture Background Below you see a simple picture of how the different pieces co-exist. The QA Application is how you interact with the hardware. It is the screen of the oscilloscope or power supply that runs on your PC. And of course, the QA Hardware is the physical box that captures the different signals required. And the QA application and QA hardware connect over USB.

The User Application can be written by anyone. What is important is how the user application connects to the QuantAsylum application. Historically, applications have relied on GPIB, which is a popular (albeit...

Power Quality Analysis with the QA100

by admin on Sunday, March 09, 2014 11:03 AM
Overview Note: 16-Mar-2014: The Power Quality Analyzer app is located here

We’re finishing up a free application for the QA100 that will let you turn your scope into a single-phase power quality analyzer and recorder. A power quality analyzer allows you to look at the short and long-term quality of AC power, and also gives insight into how a load consumes that power. These tools are useful to those trying to diagnose power quality problems or to those working on advanced consumer electronics that might be concerned with power factor correction and the Energy Star (or other) power factor requirements for consumer electronics.

To use the application, you need a QA100 oscilloscope. You will also need a differential probe and current clamp suitable for the power you wish to measure. DO NOT ATTEMPT TO USE THE QA100 on line voltages without a differential probe. See the manual for why this isn’t a good idea if it’s not...

QA400 IMD Measurements

by admin on Tuesday, October 08, 2013 12:23 AM
Intro We will look into adding the ability to make automatic IMD (Inter-Modulation Distortion) measurements on the QA400 at some point in the future. Part of the reason we’ve held back is that there are a lot of variations that are possible in IMD measurements and it’s not yet clear if a subset will do the trick and get us 90% of the way there or not. This post will look at the types of IMD measurements, and show how these basic measurements can be made on the QA400 today.

The purpose of IMD measurements is to characterize the non-linearity of an amplifier while its being subjected to more than one tone. This is the “intermodulation” part of the Inter-Modulation Distortion Tests. THD, or Total Harmonic Distortion, is concerned with the amplifier’s ability to render a single tone.

Any amplifier that has non-linearities will “mix” two or more tones. Mixing is the process of multiplying two waveforms together. The result, in the simplest terms, is that you produce a resulting waveform that bears no...