SpectraPlus Spectrum Analyzer review

[zener_diode]

SpectraPlus is a fairly inexpensive measurement software and if paired with a
good PC Audio Interface, it makes a pretty good setup for measuring audio
circuit performance. I have the full software package and a Digital Audio Labs
interface card. Attached are spectrum plots of the output of the card connected
directly to the input. The program has a utility to generate waveforms and for
calculating the measurements such as THD+N, S/N, IMD, etc. You can download
a free trial to see how easy it is to operate. As for the audio interface card, you
can use any Windows compatible card, but I chose the DAL CarDeluxe. It has
great specs and seems to work quite well.

To get the best performance from this combination of hardware/software, I had
to make the following settings, which took me quite some time to figure out, as
well as some emails to Pioneer Hill Software as well as Digital Audio Labs.

1. The card has balanced input and output and you need to make special
cables if you are connecting to unbalanced circuits.
Input Cable: Use a balanced cable with Hot, Cold and Ground. Connect the
Hot to the signal conductor at the unbalanced end. Connect the Cold to
the ground conductor at the unbalanced end. Leave the shield floating at
the unbalanced end.
Output Cable: Use a balanced cable with Hot, Cold and Ground. Connect
the Hot to the signal conductor at the unbalanced end. Connect the shield
to the ground conductor at the unbalanced end. Leave the Cold floating.

2. The card has settings for sample rate and bit depth. Don't use the automatic
settings. They don't perform as well, probably due to processing in the Windows
operating system. Instead, use 96KHz sample rate and 16-bit depth.

3. SpectraPlus has many different settings for sample rate and bit depth as
well as stereo/mono. Use 96KHz sample rate and 24-bit depth and select "Stereo".
You can set the display to only show one channel, if that is all you need.

One last note: the above cable configuration for the input will present a 10k
load to the circuit that you are testing.

Links:

SpectraPlus: SpectraPLUS - Audio Spectrum Analyzer
Digital Audio Labs: Digital Audio Labs Home Page

Happy Testing!