Behringer DCX2496 digital X-over

Jump to Latest
J

jtalden

Member
Joined 2009
Noise on all channels

I am hoping someone here will advise me. I have read much of the thread, but could not connect it directly to my situation.
I have an HT system: sources > AV Pre/Pro > DCX's > P-Amps. I am using analog balanced connections from Pre/Pro to DCX’s and unbalanced connection to P-Amps (XLR to RCA adaptors since the P-Amps have no balanced inputs). I am getting modest amount of noise on all 9 active channels. It is just noticeable enough from my listening position that I need to correct it. The noise is still there with the connections to the Pre/Pro removed.
I assume P-Amps with balanced inputs would solve the issue?
Since that is costly I am considering putting a couple ART T8 units between the DCX’s and the power amps. http://www.artproaudio.com/products.asp?type=89&cat=15&id=108
Will this solve the problem? Any major issues with this approach?
Is this a ground loop issue due to the switch from balanced to unbalanced?
Thanks much for any comments you provide regarding this.
 
J

jtalden

Member
Joined 2009
Foxx510 said:


Have you tried using a simple resistor voltage divider to reduce the output level? I assume the amps expect a -10dB unbalanced input?
Click to expand...


AndrewT said:
Noise, what type/frequency of noise?

The output from the DCX2496 is very high.
I had to attenuate ~20dB to feed my power amps with a loud signal.
-30dB to -35dB would suit normal listening.
Click to expand...


Thanks! In listening to it again it does sound like white noise. I guess I am just hearing the noise floor. I didn't consider this with the high SN ratio spec'ed for the DCX. My amps have input level controls so I will reduce the input sensitivity there. That should lower the audible noise as you suggested. Does it help, or is it good, to then raise the DCX input levels? Will that allow the DCX to operate digitally using more of it's bit depth?
Thanks again!
 
D

doug20

Member
Joined 2009
ergo said:
I did the same for years, tried
* 6-gang volume after DAC and before custom 1 opamp stage
* 6-gang volume forming a balanced shunt regulator in each DAC output

etc. etc.

Ended up buying Jan's active output upgrade and it is defenetly the most convenient and best suited for purpose + it sounds good.

With any other solution it is not easily possible to make the needed level offset between drivers in analog domain.

Ergo
Click to expand...

Is there a link for Jan's active output upgrade, is it just an output upgrade or do we require a clock upgrade/power supply upgrade?
 
E

ergo

Member
Joined 2001
J

jtalden

Member
Joined 2009
Foxx510 said:


Have you tried using a simple resistor voltage divider to reduce the output level? I assume the amps expect a -10dB unbalanced input?
Click to expand...


AndrewT said:
Noise, what type/frequency of noise?

The output from the DCX2496 is very high.
I had to attenuate ~20dB to feed my power amps with a loud signal.
-30dB to -35dB would suit normal listening.
Click to expand...


Just a note to let you know that this advice worked out very well for me. I found I couldn't hear the noise floor at my listening position when set at -12 dB on the P-amp inputs. I actually set them to -18 so the noise floor is now barely detectable even with my ear very near the speakers. I also increased the input level to the DCX's +9 dB and now it is operating nearer to its ideal range. I also adjusted the Pre/Pro source input trims a little so that the Pre/Pro volume level is near normal.
All is very good now. - THANKS!
Regards,
John
 
D

doug20

Member
Joined 2009
Studley said:
I am looking at buying a DCX and ideally using its digital input to avoid the multiple conversions when using analog inputs. However my digital sources have BNC outputs. What is the best solution please?
Click to expand...


I have several matrix switches in my house that are BNC connections and I send digital audio over them. I use simple BNC to RCA adapters, they are cheap and they work.
 
DorinD

DorinD

Member
Joined 2005
homebuilthifi.com/project/5604
autopoiesis

autopoiesis

Member
Joined 2007
linearaudio.nl 6-channel vol relative level maintenance at volume extremes

I mailed Jan Didden last night regarding his 6-channel vol control for the DCX (http://linearaudio.nl/6chan-1.htm).

He replied this morning:))) as follows; I post here with his encouragement. I hadn't seen the relative gain issue in Q3 addressed elsewhere, but Jan has clearly forseen and handled this well in his implementation.


1. Before purchase [of my DCX] I knew I'd have gain/level issues and that DCX +22bBu out into [Peter Daniels gainclones] LM3875 max ~0dBu in on 112dB/1W (horned) highs might be noisy.

No decent mic to measure with, but it's roughly equivalent to a noisy PC per side. Noise is broadband - no hum/buzz or particular characteristic; same if preamp is off; GCs are almost inaudible @10cm with DCX unplugged. [...]

Given the following gain, and sensitivity, I think it's just the noisefloor - does this strike you as normal or excessive? Can it be 'fixed' with your AA kit?

[Jan Didden]: Yes, I think the relatively high (Pro-level) gain of the DCX stock output stage with your speaker sensitivity causes the high noise levels.

2. With the AA kit, max out is ~16dBu (5VRMS), what is the maximum input?

[Jan Didden]: On the digital side, the max input is of course 0dB digital, on the analog side max input is also around 5VRMS but note that my mod also introduces input analog level control so there's no practical limit there. Anything from a few 100mV to several V's can be accomodated easily.

3. "Balance keeps channel offset intact" This got me thinking - my woofer sensitivity is 102dB/1W (two way boxes). Manufacturer's recommendations are +12bB relative gain on Lo. So, say: ch1/3 (Lo's) at 0dB, and ch2/4 (Hi's) at -12dB, but what is the behaviour of the volume control at extremes? Is it arrested across the board the moment *any* channel hits peak/min (in my case effectively limiting volume range to +6 / -48dB), or if I keep on increasing the volume after Lo ch1/3 hit the +6dB maximum, will ch2/4 *keep* rising another 12dB?

[Jan Didden]: First of all, with my mod, the config is ch 1&2 = lo, ch 3&4 = mid, ch 5&6 =hi. Just a matter of correct setup on the DCX.

And yes, it is limiting at the moment *any* channel hits the min/max limit. That way, no chance to disturb the relative levels. But it also means if you have very high relative level differences between say lo and hi (like 24dB delta) your control range gets smaller. If that is a problem in your particular case, I can provide you with a custom controller that has larger range, just let me know when you order your kit from Pilgham.

I see from the CS3318 datasheet that values outside the permitted range are accepted - implying that the highs would indeed keep rising.

But if so, is the 12dB offset recovered on the way back down?

[Jan Didden]: See above - the highs don't keep on rising. All levels are controlled in my kit, not in the CS itself.
Click to expand...

I hope this is of interest (and I'll be ordering one forthwith).

Many thanks to Jan; and also all other posters on this thread. - the quality is exemplary.

Best wishes,
Steve
 
DorinD

DorinD

Member
Joined 2005
homebuilthifi.com/project/5604
Another big question for me but on DEQ2496

Sorry guys, I have a specific question on DEQ2496's features and I'm thinking maybe here, on the brother DCX2496 I'll get the answer from more informed people.

I intend to use the AUX analog out to delay a subwoofer with about 15ms. But, in the same time, I want to be sure that the digital out remains undelayed.

My concern is generated by the fact that AUX and digital outs are treated everywhere in the user manual as one block. And the Main analog out as the second block. Any of the first or the second block can be delayed one after the other but it is not clear if the delay is refering only at the analog outs or include also the digital out.

Hope you've got my point. Thank you very much!

Dorin
 
You must log in or register to reply here.
Top Bottom