I2S input 1 sounds different than input 2


#1

I recently connected a NuWave Phono Converter to my DirectStream DAC. I’ve noticed that when I plug it into I2S2, it sounds rolled off and lifeless, in I2S1 it sounds great the same as it does thru the Analog output. The advanced settings I can see appear to be the same on I2S1 and I2S2. I’m just unplugging the hdmi cable from one input and plugging it into the other. I thought it should sound the same in either. Is there a setting or filter I’m missing. (Not to confuse the issue, but when I do the same with the output from the transport, they sound the same.)

Thanks for any help or ideas.


#2

The only setting I can think of is the “phase” button. The polarity of each input is stored separately. Everything else should be identical between the two I2S inputs.


#3

I had the phase set the same for both inputs. One of the input displays has an icon below the the gear (setting icon). It looks a little like a folder, I haven’t been able why it shows on one input and not on the other.?


#4

That’s the clue - that indicates that preemphasis is detected (it’s meant to look like a falling frequency response graph). In particular it indicates that the DS is doing deemphasis (which starts falling at about 3k.)

Why is the signal detected on one input and not the other? That almost certainly has to be the DS hardware if you are using the same HDMI cable and it the channels continue to be different when keep swapping inputs. You should contact PS Audio support if you want to get to the bottom of it.


#5

That is the pre-emphasys mode. It sounds like one of the I2C pins on the HDMI connector of the one that sounds bad is shorted hi, signaling a pre-emphasys disc.

Dennis


#6

I’ll try a different HDMI cable and see if the extra icon still shows up. If it does, I guess I’ll be talking to the PS Audio folks. Thanks for the information.


#7

The falling frequency graph shows without a cable plugged into the socket. I assume that means there is an issue with that socket.


#8

Reboot the DS if you haven’t (with the power switch on the back of the DAC). If it’s still there after a reboot and no cable connected then it’s probably hardware.


#9
Ted Smith said That's the clue - that indicates that preemphasis is detected (it's meant to look like a falling frequency response graph). In particular it indicates that the DS is doing deemphasis (which starts falling at about 3k.)
I had never noticed the de emphasis symbol on the DS so I did some investigating with my PWT feeding it. Sure enough, with a toslink connection the symbol appeared. But as usual with cds with pre emphasis, there was no left channel .

I then tried the I2S HDMI cable between the PWT and DS.
With the same disc as before, the

de emphasis symbol was not present.
Also the left channel was now audible.

What do you think is happening?


#10

The specification for the indication of preemphasis is different between AES/EBU and S/PDIF, further there are flags that indicate which kind of preemphasis is done that often aren’t implemented. The bottom line is that the preemphasis flags aren’t entirely reliable on AES/EBU and S/PDIF. The I2S connections that PS Audio use indicate the presence of preemphasis with a separate line so that’s not ambiguous. I’d expect the PWT to be consistent between all outputs, but I’m not an expert about the PWT and I do know that preemphasis detection is a pain in the neck.

I do know that there was a bug in the DS that seemed to see preemphasis when there was none and the only way to get rid of sporadic preemphasis indications once they started was to power the DS off and then back on. This could confuse experiments like yours. I don’t know the details about the bug or which releases it affected.