Originally Posted by sfogg
Gary,

"again everything was working perfect, all 4 PCM outputs are perfect"

So everyone knows... I recently found a condition where one or more outputs can on occasion mis-configure itself and you will get noise/distortion on an output, but never on all of them. Power cycle the card and the next time they all may work fine.

(Begin boring hardware explanation of the problem)

The problem is the chips I am using use the same set of pins as inputs (high or low) for configuring them and then after so many milliseconds of time after startup those pins immediately become outputs. I believe the problem pops up when the card is fed from a current limited 5v power source. What happens is in this case one or more chips lag behind the others on startup, they start running later then the others. So one or more of the chips configure themselves properly, then switch those pins to outputs and change the signal the lagging chips see which are still using those pins as inputs for configuration. As such those lagging chips configure themselves improperly and then don't properly read the serial data inputs which results in noise or distortion on their outputs. That is why when this occurs it will never occur on all four outputs, at least one will be working properly and it may or may not be the same one on multiple power cycles.

(End boring hardware explanation)

I have only seen this occur once on the 4x cards but I have altered their circuit slightly to correct for this. Gary you may have noticed in the last batch of cards you bought they had an additional capacitor on them. What that does is hold all the chips in a reset state longer while the card is first powered so that all chips start running at the same time and this corrects for this potential problem.

If all of Jim's outputs have noise in them then this isn't the issue at all. But if one or more do and if that potentially varies on power cycles then this could be the problem. Which is why I asked Jim to test each output.

Shawn


yes Shawn, I was wondering about that, glad to hear you took care of that

Jim, Shawn is dead right, you should connect the PCM outputs to a standard receiver on a digital coaxial input and check them out with a 7.1 channel blu-ray, each output will be a 2 channel 48khz signal in that usage

also make sure dynamic range control is turned to OFF in the Oppo menu, destroys the signal

-Gary Murrell
http://www.custom-ht.com/oppopowerbuy.html
My Personal HT setup