Go Back   Home > Forums > Blogs

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Old

Low Distortion DDS based dual channel audio synthesiser

Posted 24th December 2013 at 01:40 AM by googlyone

Well now I am on holidays over XMAS I got the time to really put in a solid chunk of time on the DDS based synthesiser.

Previous blog entries describe the PIC32MX based core to this. The thing works like a charm...

To get decent precision on the sinewave I have implemented an interpolation on a high precision Sinewave lookup table.
- The DDS references into a 12 bit "long", 24 bit "amplitude" precision sinewave LUT.
- Of itself this gives mediocre spurs, which in a DDS are heavily dependent on the frequency, but seem to result in 85-90dBc spurs. There is a fair hash of these without treatment.
- By adding a linear interpolation between samples in the Sinewave Lookup table, the spurs come out as shown below...

Click image for larger version

Name:	1KHz Sinewave FFT.png
Views:	125
Size:	153.6 KB
ID:	1199

- The interpolation is actually quite simple in concept:
- The top 12 bits of the DDS Phase Accumulator looks up the "Sine Sample"
...
Attached Thumbnails
Click image for larger version

Name:	1-2KHz sweep FFT.png
Views:	50
Size:	112.8 KB
ID:	1200  
diyAudio Member
Posted in Uncategorized
Views 429 Comments 9 googlyone is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 04:02 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2