Behringer DCX2496 digital X-over

[Egil]

DCX2496 @ HISS


I want to bi-amp some Waveguide speakers im currently working on, and im using a Behringer DCX 2496 as an active crossover.

• CD: BMS 4550 (driven by an Emotiva XPA-3: Emotiva Audio XPA-3 Three Channel Power Amplifier )
• LF: JBL 2226H (driven by a Behringer EP2500)

There is a 33uf capacitator on the CD.

Here is a picture of how everything is set up:

An externally hosted image should be here but it was not working when we last tested it.

I just bought the Samson S Converter, hoping it would take care of the hiss problem.. it didn't..


- When I turn off the DCX 2496, the noise is basically gone (you can hear some really low hiss. If I then turn off the Emotiva XPA-3, the noise is completely gone, naturally. So I assume that LOW-lvl hiss is caused by the Emotiva? If it was like that I would be more than satisified)

- There is noise regardless of where my AVR level is (maxed or off), and the noise doesn't get louder/lower when playing with the AVR level

- I tried plugging the DCX2496 and Emotiva XPA-3 in a plug with ground wiring - same noise

- I have even tried another DCX2496 (my brothers), same noise !

- I connected the CDs to the same speaker outputs on the EP2500, driving the JBLs, using banana plugs.. - I did this just to see if there was noise coming from the CDs with a PRO-amp as well.. I didn't play any music of course. The noise was still there.. gain on the EP2500 was set at 1/3, I forgot to check if the hiss went away if I turned it lower.. but I can try that again.

- If I MUTE the CD on the DCX2496, the noise is still there !

- Btw, the noise is A N N O Y I N G ! You can hear it so loud & clear when im sitting at the LP 5m away.. im still able to enjoy music if I just crank it up a bit.. but I don't think I can live with that hiss.



I just bought the Samson S-converter, the only difference it made was that the VU-meter has more green lights than before (from basically no green lights to 2-3 green lights on the output/inputs.. except on the CDs, there is just one green light on that when playing a loud/dynamic song).
Is it any point having the Samson S-converter at all, or should I just try and get the money back for it ?

The thing I haven't tried so far, is using an attenuator of some sort. It's a bit greek to me, but I guess I can google it and see if I find some online shop I can buy some pre-made wires from, or an L-pad or something ?

Or maybe I am missing something obvious that can fix my hiss issue in another way ?

Any tips ?

 

[Saurav]

Your gain structure is wrong. Does the Emotiva have a volume control? if it does, turn it down, and turn up the gain in the DCX on that channel. That should reduce the hiss. I had the same problem and that's the only thing that fixed it.

The noise was still there.. gain on the EP2500 was set at 1/3, I forgot to check if the hiss went away if I turned it lower.. but I can try that again.

I would expect that it will.

 

[doug20]

Your gain structure is wrong. Does the Emotiva have a volume control? if it does, turn it down, and turn up the gain in the DCX on that channel. That should reduce the hiss. I had the same problem and that's the only thing that fixed it.



I would expect that it will.

Emotiva amps do not have gain structers. I wish all these consumer amps did have gain control

 

[doug20]

If I MUTE the CD on the DCX2496, the noise is still there !

Turn the DCX off and with the amp still on and connected check for the hiss.


Im building some waveguides and I thought the DCX was creating the "hiss" in my Waveguide/CD (also the BMS4550) but I turned off the DCX and the hiss was still there. Its my amp Im going to try different amps to test out if its just the amp (Outlaw monoblocks).

its about a 56 dB SPL hiss checked using my digital SPL RS meter.

btw, what are your crossover settings for that BMS4550? Im just starting my measurements. Too funny about your connections. Im using the Outlaw monoblocks for my CD (no gain control ) and the Behringer A500 amp (with gain control) for my TD12M woofers. Very similar setup.

 

[Egil]

Problem solved!
I hooked up the Samson S-converter from the Emotiva-> DCX2496, and by adjusting the level on the S-converter, I finally got rid of the HISS! (If I put my ear close to the horn, I can heae some hiss, but I don't care - it's non existent 2m away!)

I guess I was a bit too hasty

I think my hiss was around 56dB as well, if I remember correctly. I used the same SPL meter to measure with.

I haven't started with measurements yet, but I've been playing around with the xover at 1000hz, 1100hz, and 1300hz - using L-R 12 slopes. I have a LP at 94hz, 12dB octave, +3dB for more "thump in the chest". I will start taking measurements soon, try to get a somewhat flat response, and tweak by ear after that. Will be interesting to know where you end up adjusting your BMS 4550 I would have used some TD woofers myself, if it wasn't because I already had those JBL 2226Hs (that I've used as midbass punch from ~50-150hz).

 

[doug20]

Cool, I might try my S-converter also to remove that hiss. Of course what does that do to your output?

Once I get HOLM to stop crashing (another topic).

Do you have a build thread?

 

[mige0]

Hi janneman

What is the output level of your mod compared to the stock unit?

Michael

 

[jan.didden]

Hi janneman

What is the output level of your mod compared to the stock unit?

Michael

The output of my mod, with all DCX levels at 0dB is 2.4V RMS for digital max level. The stock unit gives about 10dB more IIRC.
But it's really unimportant as my remote analog level control goes from +6dB (4.8V RMS) to -60dB in 0.5dB steps.

jd

 

[mige0]

The output of my mod, with all DCX levels at 0dB is 2.4V RMS for digital max level. The stock unit gives about 10dB more IIRC.
But it's really unimportant as my remote analog level control goes from +6dB (4.8V RMS) to -60dB in 0.5dB steps.

jd

Thanks for that info.
Regarding gain structure for usual home-fi units this certainly is a better match and thus accounts for "less hiss problems" - many here are struggling with - clever choice !


Michael

 

[boconnor]

There is an erratum sheet to the data sheet for the receiver chip that acknowledges the problem, but some never show it, apparently.

http://www.linearaudio.nl/Miscellaneous/CS8420 errata.pdf

jd

Thanks for the PDF. I don't know enough about jitter to interpret the graph - does a variation in jitter frequency attenuation mean an equivalent change in audible frequency response?

 

[Saurav]

Problem solved!
I hooked up the Samson S-converter from the Emotiva-> DCX2496, and by adjusting the level on the S-converter, I finally got rid of the HISS!

So the S-converter is essentially a volume control of some sort? That's good that you got the hiss taken care of.

 

[jan.didden]

Thanks for the PDF. I don't know enough about jitter to interpret the graph - does a variation in jitter frequency attenuation mean an equivalent change in audible frequency response?

No this is not a freq response for the signal - it shows the jitter response. If the jitter response is, say, 20dB down that means that the jitter at that freq is attenuated by 20dB. If there is jitter gain, like in the one curve that goes to +6dB, it means jitter is amplified, in this case doubled (6dB is factor 2).

jd

 

[boconnor]

No this is not a freq response for the signal - it shows the jitter response. If the jitter response is, say, 20dB down that means that the jitter at that freq is attenuated by 20dB. If there is jitter gain, like in the one curve that goes to +6dB, it means jitter is amplified, in this case doubled (6dB is factor 2).

jd

Yep, I get that. My question was more about the link between non-flat jitter response and audible frequency response.

Just trying to understand this. So, perhaps this way of expressing the question is clearer )) What is the relationship between a non-flat jitter response and the resulting audio frequency response? Is the relationship one-to-one? For instance, does a non-flat jitter response of say +6db lead to a +6db non-flat frequency response? If not, what is the relationship?

 

[taotao]

ak4393 --> ina134 -->out, what about cinch ground?

Hello,

I want to use ina134 for balanced to single end conversion.
According to datasheet (http://www.datasheetcatalog.org/datasheet/BurrBrown/mXqwtsv.pdf page8) , pin6 (jumpered to pin5) goes to + out.
Where do I put - (ground)out ? to pin1? Or leave it floated?

Thanks for explanation.

Regards
Olaf

 

[nvrgdenuf]

I asked this before and didnt get any response, so hopefully the 'helpful' people will read it this time.

I want to install input/output transformers in the DCX and will be using the Edcor. I think the 600/600 seems to be what I have found recommended for the output, but what about the input? 600/150 or 600/10k? Do I need to hook the vcom voltage to the CT? With the 600ohms toward the dac?
Anything on the output CT?
thanks to anyone offering help.
andy

 

[doug20]

What about this for reducing the DCX hiss...

XLR attenuator (Pad 10dB) @ parts express.

http://www.parts-express.com/pe/show...ource=googleps

 

[jan.didden]

I asked this before and didnt get any response, so hopefully the 'helpful' people will read it this time.

I want to install input/output transformers in the DCX and will be using the Edcor. I think the 600/600 seems to be what I have found recommended for the output, but what about the input? 600/150 or 600/10k? Do I need to hook the vcom voltage to the CT? With the 600ohms toward the dac?
Anything on the output CT?
thanks to anyone offering help.
andy

If the sensitivity at the input is OK for you, you should take a 1:1 transformer. I guess you use the stock input circuitry?
A 600 ohms is OK if your source can drive low impedances, otherwise take something like 2k:2k or even 10K:10K, you probably get better low freq response.

jd

 

[nvrgdenuf]

Hi Jan thanks,
Right now I am using the Dig straight In, no I/O boards, but want to add analog capability for some experiments. I would be using computer sound card, cdp with tube output, dac with tube output. You recommend a 10k/10k then? I have found some of your other posts, and believe you mention needing the CT to a 2.5volt souce using a voltage divider (which I would need help with) or using the VCom.
Or was the 10k/10k for the output trans?
Amplifier might be LM3886 or even my Pioneer receiver for now.
thank you

 

[jan.didden]

Hi Jan thanks,
Right now I am using the Dig straight In, no I/O boards, but want to add analog capability for some experiments. I would be using computer sound card, cdp with tube output, dac with tube output. You recommend a 10k/10k then? I have found some of your other posts, and believe you mention needing the CT to a 2.5volt souce using a voltage divider (which I would need help with) or using the VCom.
Or was the 10k/10k for the output trans?
Amplifier might be LM3886 or even my Pioneer receiver for now.
thank you

The need for the 2.5V CT is only if you drive the ADC directly, which is the case with my output board replacement mod with the remote 6-channel vol control.

But if you just want to drive the stock analog input that is not required.
With all due respect, I don't think using an input xformer with the stock input makes any sense. It can only color your sound.

jd

 

[nvrgdenuf]

Hi Jan,
You are correct, I have no input board. It would go straight to the ribbon connector on the main board.
andy