I think I have a problem with my Digital Input Board


#1

I’ve had my DS upgrade in place for a while. I had no troubles installing and it has been trouble free until now. Using I2S, I’ve been having intermittent problems where 1) 24/192 doesn’t register at all and 2) even when working sometime times I hear distortion - it’s like the gain has increased - this happens also at 88.2.

This happens on both I2S inputs and when i tried i was unable to use USB except sometimes at 48k. If I jiggle the hdmi cable, i can get things normal but any sort of movement of the cable causes problem. It’s not the cable itself because i’ve tried a few.

Any ideas? I haven’t disassembled yet but I’m hoping it’s a short or something. I’m hoping it’s just the input board since I could probably replace in time for the holiday weekend.


#2

That’s a new one on me. Perhaps there’s a problem with the I2S cable you’re using? Can you try another cable to make sure?

It seems odd you’d have both inputs go bad, like a connector, at the same time.


#3

Ok. The cable i was using as well as my spare both showed the symptoms. I got a couple of new cables and the problem is gone. As near as I can figure since both original cable had metal casings around the plugs (instead of molded plastic) maybe the grounding was causing a short? Beats me but things are fine now. I really doubted it was the cable since both I origninally tried had the same reaction. I can also recreate it going back to those cables.


#4

Grounding sounds like the most likely problem. Perhaps your I2S source is on the opposite polarity of the house’s AC wiring? Or perhaps you are using balanced power for some of your components but not all of them? If the AC plug on the I2S happens to be a two prong plug that isn’t keyed you could flip it over.


#5

Neither of those but should the casing of the hdmi plug be on the same path as the hdmi connector itself? On one end my continuity test shows the casing and the plug to be on the same circuit…not so on the other end of the cable.


#6

A volt meter is the best way to check out grounding issues and/or phasing… If there’s a DC offset bigger than, say, 5 or 6 volts you might have a grounding problem. But you also need to check the AC voltage - if that’s very big you either have a grounding problem or your components aren’t on the same side of the circuit breaker box (or you have some device with a floating ground… In my case a laptop.) It’s not always bad to have your components on opposite phases, but when you end up with an interconnect’s ground trying to ground out, say, 120VAC that can cause all sorts of data errors…


#7

Ouch. Ok will check. You don’t think my DS is damaged?


#8

Probably not - the inputs are reasonably well protected if there’s not a lot of current. But they can be less reliable when riding on a 120 VAC signal :slight_smile:

Most of the time even if there’s something wrong there’s no real problem until some component fails and a safety ground goes live. With symptoms like yours it’s worth checking for voltage offset with a volt meter, but I doubt that it’s a problem most of the time.

Since devices with two prong plugs are often floating sometimes I need to hook up a USB cable or something else with a solid ground to get my laptop to work with a digital coax connection…