Behringer DCX2496 digital X-over

[jan.didden]

Originally Posted by MurphyUHF10

[snip] Once I did this, hum/buzz vanishes almost completely.. [snip]Cheers..
CM

Excellent! Well done!

Originally Posted by MurphyUHF10

[snip] Can the Didden Linear PSU handle an extra 300mA..?? Do you see any issues here with taking power from X3 pin 1 & 2.. At least I wouldn't need to worry about grounding :-)
Cheers..
CM

Sorry, no way! I had to bend over backwards to get that linear supply within the space and dissipation constraints as it is - it gets pretty warm, although not critically. But another 300mA is out of the question.

Originally Posted by MurphyUHF10

[snip] However, when I mute/unmute on the remote, or change volumes etc, I get loud "pop" with every button press on the remote..?
[snip]Cheers..
CM

That's unusual. Can you verify whether there is DC offset at the outputs? If that would be the case, changinging level or muting would change the offset level and that could cause plops. If the offset is low but not very low you get what is called 'zipper noise' but you say plop so I guess it's not subtle.
You can check that without signal.

jan

[MurphyUHF10]

Originally Posted by janneman

But another 300mA is out of the question.jan

Hi Jan, ok I understand :-(

Originally Posted by janneman

Can you verify whether there is DC offset at the outputs?

...You can check that without signal.

Yes, I get about 160mV DC across the output (XLR pin 2 & 3). With LM4562's I get only 1 or 2mV..

The 'Pop" is not subtle. It's very distrubing, especially with no music! With music it's not as bad, but still noticeable. With 4562's, no Pop's, dead quiet in all respects (I can see you grinning)..

Ta
CM

[jan.didden]

Originally Posted by MurphyUHF10

Yes, I get about 160mV DC across the output (XLR pin 2 & 3). With LM4562's I get only 1 or 2mV..

The 'Pop" is not subtle. It's very distrubing, especially with no music! With music it's not as bad, but still noticeable. With 4562's, no Pop's, dead quiet in all respects (I can see you grinning)..

Ta
CM

I think you just answered your own question. 160mV is unacceptably high in this application.
1 to 2mV is also what I measure.
If you switch level, whether stepping or muting, you change the offset in level as well. Stepping DC sound like, well, pops

There's no practical problem as long as the pops don't blow your speakers, but as you say, it's annoying.
If you really want to continue to use the discrete opamps, you might be able to insert a coupling capacitor on it's output to AC couple it.
But then you're really bending over backwards and you should be really sure it's worthwhile.

jan

[MurphyUHF10]

Hi Jan,

Yes, Perhaps I just put these discrete modules back in the drawer for another project..

Worth mentioning however, is that I did receive a reply from Burson,, they suggest shortening the wires from the external power supply to the op-amp modules, and also said to put "local power coupling capacitor across the power pins, 100uF or 200uF Good quality cap".. They have not replied to my query about the high DC offest (as yet). I might try these 2 suggestions,, and after that if I'm still not satisfied,, back in the drawer they go!!

What is a "Good quality local power coupling capacitor"..??

Thanks
CM

[jan.didden]

Originally Posted by MurphyUHF10

Hi Jan,

Yes, Perhaps I just put these discrete modules back in the drawer for another project..

Worth mentioning however, is that I did receive a reply from Burson,, they suggest shortening the wires from the external power supply to the op-amp modules, and also said to put "local power coupling capacitor across the power pins, 100uF or 200uF Good quality cap".. They have not replied to my query about the high DC offest (as yet). I might try these 2 suggestions,, and after that if I'm still not satisfied,, back in the drawer they go!!

What is a "Good quality local power coupling capacitor"..??

Thanks
CM

Yes, a knee-jerk reaction to hum is often throwing cap at it.
Which is unfortunate because I never have seen a hum problem that was solved by capacitors.
Hum and buzz always have a very specific cause and if you fix the cause, you fix the hum/buzz.

jan

[mefistofelez]

Greetings all,

I have acquired the DCX2496, and found this thread. However, before I start sifting through the 300+ posts, I was wondering if someone could list the modifications in order of perceived bang-for-the-buck improvement.

Kindest regards,

M

[MurphyUHF10]

Originally Posted by janneman

160mV is unacceptably high in this application.

jan

Hi Jan,

Thought to mention this, just in case anyone else is facing same issue.

I heard back from Burson regarding the High DC offset.. "The DC offset can be adjust via the small blue trimpot. It does not affect class A operation, or sound quality, only used to adjust DC offset.."

Over the weekend, I will finalise the grounding layout to further minimise hum. I will shorten the "fly leads" and install 100uF & 0.1uf across the power pins (4 & 8) of the Discrete modules, and I will also adjust the DC offset as low as I can get it..

I will report back with some reults in a few days!!

Thanks
CM

[MurphyUHF10]

Originally Posted by mefistofelez

Greetings all,

I have acquired the DCX2496, and found this thread. However, before I start sifting through the 300+ posts, I was wondering if someone could list the modifications in order of perceived bang-for-the-buck improvement.

Kindest regards,

M

Hi M,
Although you seek a quick answer,, it might be best to read through this entire thread!! Treat it like a novel, each night you read 15 or 20 pages :-)

Personally, I have the Didden / Oettle combination, and it works great! But perhaps not "bang for buck".. You will get lots of ideas that are 'bang for buck' if you read through this thread.. It's good fun ;-)

Cheers,
CM

[autopoiesis]

Hi mefistofelez,

1. Didden Active I/O
2. Didden linear PSU
3. Oettle SRC/clock

This is the order I fitted them, over a couple of years, and in order of increasing subtlety and decreasing cost. I suspect that if you fitted the SRC mod on a stock unit, you might not notice the improvement, and give up. With the other two in place, it was more like icing on the cake.

Value-wise, although the active I/O is not cheap, it does so much to improve not just the sonics, but also the usability of the unit (signal levels, remote control). It's really a quantum leap I would consider essential.

All three are certainly worthwhile, and can be spread over several accounting periods, should WAF be an issue

Have fun!
autop

[mefistofelez]

Hi MurphyUHF10,

I will read it, but I thought that a synopsis would be beneficial, so that I do not get lost.

Hi autopoiesis,

Thank you very much.

Kindest regards,

M