Ive posted about this some time back in the thread I created when I first posted about the DAC.
Now the popping whilst diminished still persists.
I dont think this is anything to do with the digital side of things and am more concerned with the power supply.
OK well ive got LM317 and 337 performing regulation at about 16volts for the IV stage and output filter. This is not the problem because when the DAC output is muted there is silence.
Ive got LM340 @5v performing regulation for the DAC PCM1798 and an LM1086 @3.3v for the digital circuitry in the DAC and the DIR1703.
When I was first trouble shooting with the DAC I disconnected the DC powersupply to the main board several times and once connected the negative rail to the positive input on the board.
The caps in the power supply were fully charged, thus 4700uf @25 volts powered its way to everything. This didnt seem to affect anything performance wise, still getting the correct voltages everywhere, but the LM1086 got waaay hotter then it did previously as far as i am aware.
When I get the popping its quite loud and occurs mostly when music starts to play (ie there is sudden demand, albeit quite small, for current) and can either occur in the left or right channel but mainly in both at the same time. The popping can occur whenever it really wants to, but is worse when loud music is playing. This is not loud as in the volume control is turned up obviously, but when a loud passage plays.
Anyone any ideas?
Are those regs suited to this application?
Matt
Now the popping whilst diminished still persists.
I dont think this is anything to do with the digital side of things and am more concerned with the power supply.
OK well ive got LM317 and 337 performing regulation at about 16volts for the IV stage and output filter. This is not the problem because when the DAC output is muted there is silence.
Ive got LM340 @5v performing regulation for the DAC PCM1798 and an LM1086 @3.3v for the digital circuitry in the DAC and the DIR1703.
When I was first trouble shooting with the DAC I disconnected the DC powersupply to the main board several times and once connected the negative rail to the positive input on the board.
The caps in the power supply were fully charged, thus 4700uf @25 volts powered its way to everything. This didnt seem to affect anything performance wise, still getting the correct voltages everywhere, but the LM1086 got waaay hotter then it did previously as far as i am aware.
When I get the popping its quite loud and occurs mostly when music starts to play (ie there is sudden demand, albeit quite small, for current) and can either occur in the left or right channel but mainly in both at the same time. The popping can occur whenever it really wants to, but is worse when loud music is playing. This is not loud as in the volume control is turned up obviously, but when a loud passage plays.
Anyone any ideas?
Are those regs suited to this application?
Matt
Check out Walt Jung regulators, these are very low noise and great transient responce. There are number of people copying these designs so PCB are out their. Also http://www.audioxpress.com/ sales the older designs of this PCB and it work very good.
http://home.comcast.net/~walt-jung/wsb/html/view.cgi-showresources.html-TopRes-Walt-27s-20PDFs.html
http://home.comcast.net/~walt-jung/wsb/html/view.cgi-showresources.html-TopRes-Walt-27s-20PDFs.html
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