Yes, much better at distortion at the audio range but not so good in the low bass range, under 100 Hz its 0.3%. But not sure if you can hear a distortion at that small difference.
The trade off for low distortion in audio generators is far lower frequency stability and lower ranges for frequency generation, but those are not important issues for audio. To get a combination of high stability and distortion means costly equipment. For example a reference DDS type generator:
http://www.thinksrs.com/products/DS360.htm, is about 0.001% in the audio range and runs $4000.
See this thread too, it has more details and pictures:
https://www.eevblog.com/forum/index.php?topic=1392.msg32213#msg32213From the link, here are some major spec differences,
Instek 1003 is in green and an ! point :
10 Hz to
1 MHz, 5 ranges;
! 3MHzFrequency
Accuracy ±(3% + 1Hz),
! <20ppm, or .002%Distortion Factor
500 Hz to 20 kHz, 0.02% or less,
! ~0.18% 0.5 Hz - 3 MHz, 100 Hz to 100 kHz, 0.05% or less
50 Hz to 200 kHz,
0.3% or less
20 Hz to 500 kHz, 0.5% or less
10 Hz to 1 MHz, 1.5% or less
SQUARE WAVE
Rise & Fall Time Less than
200 nS,
! < 5nsDuty Ratio
50% ±5% ! +/- 90%For comparison, Tek SG505 is one notable audio generator, you can see the specs. It appears now and then on eBay from $100-200, but you also have to rig up its power supply properly, not just any power supply will do as it may inject noise into the electronics. Its harmonic distortion is rated at ~ 0.0008%, far better than the SRS.
http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBYQFjAA&url=http%3A%2F%2Fwww.testequipmentconnection.com%2Fspecs%2FTEK%2520SG5010%2CSG505%2520SPECS.PDF&rct=j&q=tek%20sg505&ei=qlhNTca-IoL7lwfm7r3pDw&usg=AFQjCNEof2zEgqsAKUOHSjKIYnlZh_hP0A&sig2=mxnDc5RHCbR-UrqhZrwbmA&cad=rjaThe question really now becomes, which is more important, distortion or stability?
Most humans cannot hear distortion below 1% or ~ -40dB. The 1003 is specified 0.18% or - 55dB. Its not the best is you believe audiophiles can hear 0.1% or less. Here's a sample curve of distortion versus frequency on human hearing and is similar to academic hearing tests, extrapolating the X axis will show -55dB is out of range of human hearing:
http://www.axiomaudio.com/distortion.htmlLastly, both Instek and Tek are very reputable, so you can believe its spec sheets are accurate. Note, the Instek 1003 might be a rebrand of an OEM of Quakko, but the Instek version is tested to its spec sheet, whereas the Quakko has more capability but unknown fidelity.
Sorry to intervine...
How about Instek GAG-810 Audio Generator, for someone who intend to used it only in audio work?
http://www.testequity.com/products/1039/
It says: 500 Hz to 20 kHz, 0.02% or less, distorsion factor.
Isn't it better than SFG 1003?
Any other suggestions, on a buget?
II