'Hot' signal input to DCX2496 problem - Page 3

Saurav · 25th June 2010, 03:37 AM

Quote:

Originally Posted by dabbler

How many bits does 6db equate to? And how many bits of loss would be noticable?

I'm no expert here, so my math could be wrong. I think 6dB represents 1/4th. Not sure if that's power or voltage though. Worst case it's voltage, so 1/4th would mean losing 2 bits (I think each bit multiplies / divides by 2). The DCX2496 has 24-bit internal processing, and the signal coming in from the CD player is 16 bits, so in theory you have 8 bits to burn without losing any of the original signal. But I have gains and cuts in the EQ section, so I can't really say if I'm dropping any bits from end to end. I hope not

Quote:

Actually, im confused, can I just use the RCA cable i have now and plug that into the DVD players digital output and then run the cable to the XLR adaptor in DCX input A? Then set input A to digital on the DCX software?

I used to do that before I got the AES/EBU to S/PDIF converter, and it worked fine. I can't say that one sounds better than the other, because many other things changed at the same time.

dabbler · 25th June 2010, 12:17 PM

Quote:

Originally Posted by panomaniac

Yes, you can. There "may" be better ways to do it, but this will certainly work.
There is no video on that digital signal, no worries.

When you get the time to systematically test the DCX, you want to know if you have noise when there is no music playing (no signal). Test each of the 6 outputs for noise with no signal. Test for any difference with the channel muted or not. Also with inputs muted or not. That will be 4 tests per channel:

Input + output muted
Input unmuted, output muted
Input muted, output unmuted
Input + output unmuted

Seems like a lot, but it will go really fast. Keep notes!
What we are looking for is if you have any noise that is just coming from the DCX circuitry. If it is not, then it most be signal related. That's the next step.

NO MUSIC: Tried all of the above and have zero noise in all combinations.

MUSIC PLAYING: With digital signal in the input VU meters are hovering around -2 db, just below clipping. I have also noticed that channels 5 and 6 are constantly clipping when playing the signal with top bar illuminated red at all times. Note I am only using channels 1 and 4 for output, 5 and 6 are not being used at all. Muting 5 and 6 does nothing. Muting 1 and 4 gets rid of the distortion but also the music.

dabbler · 25th June 2010, 01:10 PM

Tried a new setup using channel 1 and 3 output. Same problem (heavy distortion + clicks and pops from left channel) however channel 5 and 6 VU meters show no signal so must have been a dodgy setup earlier.

Brett · 25th June 2010, 01:21 PM

Quote:

Originally Posted by Saurav

I'm no expert here, so my math could be wrong. I think 6dB represents 1/4th.

6dB is one bit in voltage terms.

Pano · 25th June 2010, 02:34 PM

OK, good test. It's not idle noise but something related to signal.
Do the clicks and pops come at any time, or only on peak levels?

Do you have any EQ turned on? It's possible to boost the unit into clipping with EQ boost. Generally the level is lower on the outputs than the inputs when using just crossovers. Without any level or EQ boost, the outputs will not clip if the inputs don't. And the digital input only clips if the digital recording is clipped. I rarely see that.

Do you see any relation between the noise and the VU meters?

If you can get spdif out of your computer or simply burn a CD, I can supply some test tones for you.

WithTarragon · 03:03 PM

Quote:

Originally Posted by Brett

6dB is one bit in voltage terms.

ALSO Quoting.....

I'm no expert here, so my math could be wrong. I think 6dB represents 1/4th"
--------------------------------------------

Pressure and voltage are "20 log" quantities, while power is a 10 log quantity.

So, -6dB would be 1/2 the voltage or the 1/2 the SPL, while it would be 1/4 the power

dabbler · 02:55 PM

Quote:

Originally Posted by panomaniac

OK, good test. It's not idle noise but something related to signal.
Do the clicks and pops come at any time, or only on peak levels?

Pops and clicks correspond to passages in music / peak levels. Louder passages = more clicks however even quiet passages get it popping and spluttering. There is also alot distortion under all that bacon frying

Quote:

Do you have any EQ turned on? It's possible to boost the unit into clipping with EQ boost. Generally the level is lower on the outputs than the inputs when using just crossovers. Without any level or EQ boost, the outputs will not clip if the inputs don't. And the digital input only clips if the digital recording is clipped. I rarely see that.

No eq, all gains double checked and are at zero. In my case the levels on the outputs are HIGHER than or atleast equal to the inputs.

Quote:

Do you see any relation between the noise and the VU meters?

Crackling is always there regardless of whether outputs are clipping or not but it does seem to spit a bit harder when it clips

Quote:

If you can get spdif out of your computer or simply burn a CD, I can supply some test tones for you.

I can give it try, thanks for your help. I must say at this point im thinking "faulty unit"

Pano · 25th June 2010, 03:43 PM

And I believe you are absolutely right. I don't know what the trouble is, but it is definitely faulty.

You should return it. Let them know that you have tested it and it's not supposed to do that. A normal unit might have a little hiss, that's all.

Good luck!

qusp · 25th June 2010, 03:49 PM

guys i'm not familiar with this device, but is there a buffer size setting like on most pro and semi-pro audio interfaces? I would think there is, and these clicks and pops sound like it is related to memory overrun. if there is somewhere to make the buffer size larger, do that, you should be able to do it live while music is playing.

I apologize if this has already been covered. doesnt explain the distortion underneath, but we could be seeing 2 separate problems here

I agree with the above though, it does sound like a dud unit. link him to this thread if he gives you any lip

dabbler · 27th June 2010, 01:33 PM

The shop I bought the unit from offered a straight swap so i'll exchange it later this week. Thanks for the help guys, I learnt a lot in the process.

Regarding digital input and attenuation after the DCX, can anyone recommend a good value 6 channel attenuator? If I can't find a decent priced one I may have to consider 3 x 2 channel stepped.

25th June 2010, 02:34 PM	#25
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	OK, good test. It's not idle noise but something related to signal. Do the clicks and pops come at any time, or only on peak levels? Do you have any EQ turned on? It's possible to boost the unit into clipping with EQ boost. Generally the level is lower on the outputs than the inputs when using just crossovers. Without any level or EQ boost, the outputs will not clip if the inputs don't. And the digital input only clips if the digital recording is clipped. I rarely see that. Do you see any relation between the noise and the VU meters? If you can get spdif out of your computer or simply burn a CD, I can supply some test tones for you. __________________ Take the Speaker Voltage Test!

25th June 2010, 03:43 PM	#28
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	And I believe you are absolutely right. I don't know what the trouble is, but it is definitely faulty. You should return it. Let them know that you have tested it and it's not supposed to do that. A normal unit might have a little hiss, that's all. Good luck! __________________ Take the Speaker Voltage Test!

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25th June 2010, 01:10 PM	#23
dabbler Account disabled at member's request Join Date: Apr 2010 Location: Between cities!	Tried a new setup using channel 1 and 3 output. Same problem (heavy distortion + clicks and pops from left channel) however channel 5 and 6 VU meters show no signal so must have been a dodgy setup earlier.

25th June 2010, 03:49 PM	#29
qusp is choosing a less facetious title... diyAudio Member Join Date: Oct 2009 Location: Brisbane, Australia	guys i'm not familiar with this device, but is there a buffer size setting like on most pro and semi-pro audio interfaces? I would think there is, and these clicks and pops sound like it is related to memory overrun. if there is somewhere to make the buffer size larger, do that, you should be able to do it live while music is playing. I apologize if this has already been covered. doesnt explain the distortion underneath, but we could be seeing 2 separate problems here I agree with the above though, it does sound like a dud unit. link him to this thread if he gives you any lip

27th June 2010, 01:33 PM	#30
dabbler Account disabled at member's request Join Date: Apr 2010 Location: Between cities!	The shop I bought the unit from offered a straight swap so i'll exchange it later this week. Thanks for the help guys, I learnt a lot in the process. Regarding digital input and attenuation after the DCX, can anyone recommend a good value 6 channel attenuator? If I can't find a decent priced one I may have to consider 3 x 2 channel stepped.