Help with ARTA Software

[dennismiller55]

Originally Posted by skidave

I thought I would add to this post by sharing this link about an active notch filter. There is quite a bit of discussion about ARTA use. Also, the other articles are great too.

Active Twin-T notch filter

The author and designer of this filter Dick Moore is a member of this forum. He has a post here discussing his filter: Build -- Active Twin-T notch filter for distortion analysis


I agree, there is a lot of useful information here. In fact, it was his website that sparked my interest in using ARTA and sound cards for spectral analysis. I plan to build his filter sometime soon.

[dennismiller55]

Originally Posted by BFNY

On many of these sound cards, the generator (DAC) is not as good as the ADC. Usually performance can be improved with a good external low distortion sine generator. HP339A, Tek SG505, etc.

Bob

Originally Posted by 5th element

Apart from consistency one thing that is important in high resolution measurements is making sure that everything is connected in a way that will keep ground loops at bay. This shouldn't be too much of an issue with a laptop and external USB interface though as the whole thing can be battery operated and thus floating and create no loops.

Ok, I have "played" around with some of the above suggestions.

I found out that my laptop generates a lot of noise with connected to the AC source. Pulling the AC jack and conducting ARTA test on battery only produce some great results in THD and THD+Noise.

As suggested by BFNY, I also got better results from my HP239 Generator.

1. The first screen grab is my setup using Hp239 to E-MU-204 to Dell Laptop (AC/DC) supply connected. The results are to not pretty.

2. The next screen grab is the same setup but with the laptop on battery power. Big difference, but I still see some 60 Hz & 180 Hz artifacts.

3. The last screen grab Laptop on battery power and Low frequency cut-off set at 400hz. This trick I found playing around with ARTA. This really improved the THD + Noise figure by ignoring the AC artifacts I assume are from overhead lights or the HP239.

I also found that my wife's Toshiba Laptop produced even poorer results both with AC/DC connected and on battery.

So everything in the setup including the PC/Laptop can impact the results. I wonder if there are laptops that are manufactured with better shielding and power supplies.

[skidave]

Dennis, I'm going to mess around with my ARTA this weekend and see if I can tweak it a bit more. My Tascam USB interface does not perform nearly as well as your E-MU. I'll post some pictures of my results. Also, I'm going to set the LFcut-off to 400hz as well and see what difference I get.

FWIW, I always use my laptops on battery when using this and any other analysis software.

Dave

[skidave]

Here are my results. Images are labeled with details. This is best I can get out of this Tascam US-100: