Using the QA403 to play .wav files

I can record ~20Seconds of audio at 48kHz (1M FFT) on the QA-403 and it sounds awesome!

But, I’d like to be able to play those .wav files I have saved and loaded, but can’t seem to (maybe I’m missing something). I can analyse the loaded .wav file I know, but playing out the outputs?

It’d be good to be able to play test pieces into amplifiers I am working on as musical content is always the sanity check after test signals and the analyzer would be already connected.

@matt would it be easy/possible to have a ‘user .wav’ file button on the generator panel like the ‘user’ weighting buttons? That could load a ‘user’ .wav for outputting/analyzing.

I saw a QA user had created a player from the QA in the bare metal thread but that’s way beyond my skills.

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Hi @restorer-john, if you right click on the RUN button in the QA40x app, you’ll see a dialog open. and one of the tabs is “Audition” where you can load a wav and play it.

Alternately, if you use Tractor you can script tests. One of the tests you can create is an audition test. This allows you to play a WAV file out of the QA40x so that an operator can check for scratchy pots. For example, think of a test for a guitar amp. You’d encode a WAV at the correct sample rate (48k) and bit depth (32-bit float). The WAV for a guitar amp would be a low-level guitar signal without any processing (distortion, reverb, delay, etc). And then, when that test is run, the WAV will play and the operator can turn all the pots and confirm there aren’t any scratchy pots with your ears. You can opt to loop the WAV too. When the operator has confirmed all the pots, they click pass.

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That is so cool. I thought I had right clicked on everything but never considered the ‘run’ button had options!

Thanks Matt!

@restorer-john I had an amp that was running on the hot side after having 1khz applied with it putting out 5w/8ohms for 30min or so. While this is not unusual, I thought I would see how it did with playing music via the “Audition” method described above. As I have just dummy loads w/out the ability to monitor what is going into them, I had no way of knowing what level the music was “playing” into my dummy loads. Luckily, I had an old Radio Shack Power meter which I was able to connect pretty easily, and adjusted the QA403 to give me peaks of a few watts. Hooking a power meter up is easy enough, but it would be neat if the software would give some kind of display as to what is happening across a known load (am guessing that is not so easy to do). The other thing that became apparent was that there was no “repeat” option for the file, just Play and Stop, and when the track was over, you had to press Stop and then Play again. It would be nice to have either a Repeat .wav file “x times” or play the file for x minutes…

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A trick I use with fixed value dummy loads is a load parallel switchable medium value resistor in series with a sacrificial bench speaker. You can take the amplfifier right up to clipping and hear it (quietly), without damaging the speaker or your ears.

Yes, that’s a great idea for the .wav file options. Is there a limit to the size of the file it currently will play? If not, we could just put the same musical piece multiple times in one file?

@restorer-john I like that suggestion to wire in some sacrificial bench speakers. I have some speakers on another bench in the same room that I use for that purpose, but then I can’t play too loud if the test may take say a few hours. I took 3 .wav files (tracks from Dave Brubeck) that were converted to 24bit, 48kbps, and merged them into a single .wav file that was about 18min long, and the QA software had no problem with that length- just have to make sure the sampling rate is set for 24kbps and the freq range is 20hz-20khz. I have a program called GOLDWAVE that I use to merge the .wav files into a large file. Not sure if Audacity can do that, but I use it to convert the ripped .wav file to 24/48.

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Note that a more flexible way to play audio files through the QA403 may be to use ASIO401 and play the file through any ASIO app.

Thanks for the advice. I have no experience with ASIO as far a measurements are concerned. I have seen discussion here about them, including the application you wrote (thanks for the footnote to it). For what I do, the QA40x is pretty much all that I need except that I have been doing some basic phase measurements, but need to use my o’scope for something…

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