Print out graphs

I’m thinking about buying a QA403 for my repair shop. Is it possible to print out graphs to give to my customers? Also, is it possible to use this with cassette and open reel tape decks? Thanks, Mike

Hi Mike.

Yes, you can print anything you want. With date/time embedded in the images. You’d be pretty unique out there if you offered traceable performance data on vintage repair work for your customers.

And the QA403 can be used with cass/RTRs- it has an inbuilt W&F test, you can do FR and THD plots, along with compensating for the inherent gap delay in rec/mon with 3 head decks.

W&F: Visualizer Wow and Flutter · QuantAsylum/QA40x Wiki · GitHub

It’s a fabulous product range that sits in a unique niche in the market. It has obsoleted several large pieces of expensive vintage test gear on my bench- some of which I have had as trusted instruments for ~35 years. No fan noise, truly tiny (the size of a Focusrite 2i2 interface), only pulls about 4W via USB, no clunky ancient operating systems/computers required for older hardware, fully balanced or SE and the software is pretty darned solid. It runs on even a low end laptop quite happily.

Basically, there’s vintage standalone instruments, with all the calibration/reliability and performance issues, then there’s soundcard hack jobs, which are just messy at the end of the day, the QA-40x and then there’s Audio Precision.

There’s a learning curve for sure, but the Q-Asylum inmates are a pretty helpful bunch and Matt is on the ball with fixes and features, as well as pushing the envelope with new products. Hope that helps.



Hi John,
Thanks for the info. I’ve decided to pull the trigger and order one. Does look like a learning curve but well worth it. I’ve been using a Tek SG 505 generator with a Tek AA 501A analyzer. The combo gives me 0.0008% THD with IMD and S/N. But the QA403 should give me that and more. Plus printouts for customers.
Thanks again, Mike

Your mentioning the SG505 had me wondering…

Here is my SG 505 into the older QA401

and here is the QA401 in loop back
(note in next post)

Note very close. The 505 has about exactly the same THD is but has more noise and 60Hz issues. Note the top of these shots where it shows the exact measurement.

Here is QA401 in loop back. The newer QA403 should do slightly better.

Here’s my left channel QA-403 loopback at a sweetspot of output and input:

The right channel is a bit worse in all measurements:

Hi @restorer-john, yes, and it’s not just your unit. There is indeed channel to channel variations present on all units. It’s inherent in the DAC and ADC. The Signal Path has some commentary on the discrepancy in the video below. On the manufacturing side, I can be sure it’s in the ADC/DAC because the channels are identical from a schematic standpoint AND YET there’s a clear mean and sigma shift between left and right channels when looking at the manufacturing data.

Generally, if you are making a measurement that is approaching the limits of the QA403, use the left channel and that may buy you a few more dB.

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I am waiting on my QA403 to arrive. Once I get a feel for it I’ll check my SG 505 to see how it compares to yours.

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Yeah I’m really curious what you find.
My SG505 is the nicer one with both options 01 and 02 , mod WR and the matching special TM504A case so it’s supposed to work better than others. I did the sweep single ended, even though it’s differential out, so I am sure I could get better results if i tried to figure out the adapter to do that. But the results are already 2x the spec.

But I literally found it in a junk bin at a ham fest as non functional. I sprayed Deoxit in the gummed up switches and it started to work. Super lucky cheap find on my part.
I have done 0 else to it. I’m sure it’s way over due for calibration but I figure at those levels I need more than a QA401 to calibrate it. I no longer have access to an audio precision.

Also sorry about “flagging” your post. I hit the wrong button. @matt please ignore the flag and my apologies. Was not intended.


I use it all the time to print out FR sweeps for customers tape machines. I’m probably going to sell my AP soon.