dcx2496 xlr-phono advice

[SpeakerBob]

Hi all,

Just received all my cable and connectors to make up the leads for the dcx.

Now, at the moment the amps are all integrated, but I intend to upgrade to power amps eventually. The amps are cyrus 1's for the mids/tweets, and Audiolab 8000a for the bass.

If I want to make the cable attenuate the pro level signal to home levels, what resistor value would I use ?

I intend to solder the resistor in series at the phono end, and will short pins 3 and 1 at the xlr end to make it unbalanced.

Is this correct ?


Cheers

Rob

 

[dhaen]

Rob,

You shouldn't normally short an XLR output, unless it's transformer coupled which is very rare, or unless it says you can. (There are 1 or 2 cross-coupled circuits that you can too, which are used in some audio desks). But generally, you mustn't.
What you can do is to take the signal between pin 2 (+) and 1 (G).

The attenuation resistor (if required) will depend on the input impedance of the amp. I suggest you try without, as the signal is already halved by only using 1/2 the balanced signal.

 

[moving_electron]

Page 20 of the manual found at:

http://www.behringer.com/DCX2496/index.cfm?lang=ENG

tells you to short pins 1 and 3 to connect unbalanced. This works fine for me on the analog ins and outs of the DEQ2496.

 

[dhaen]

If the manual says you can; you can
Much kit drives each leg with an opamp. I was considering that.

So, you're back to the attenuator....

 

[SpeakerBob]

Hi Moving_electron.

I read this in the manual, and was just looking for the online manual to post a link to. Thanks for that

I just wanted to check and make sure.

John - it says it has a servo function that recognises unbalanced configurations, I take it that would do it ?

What sort of voltage would half a pro signal give ? 7 ish volts peak ?

Cheers

Rob
Edit - John posted the above while I wrote this babble

 

[moving_electron]

I think the last line of Page 20 Section 5 of the manual says that DCX2496 reduces the output if it sees the input come in at the reduced unbalanced "home audio" level?

The servo function, also automated, recognizes the connection of the unbalanced pin assignments and changes the nominal level internally so that there is no difference in level between the input and output signals (6 dB correction).

I did not attenuate with the DEQ2496, which same connection instruction and has various shared I/O components, and all seems fine.

 

[SpeakerBob]

Yes it does, thanks Moving_electron

I'll be feeding it through aes/ebu so I guess I'll be fine. What would happen if you fed it balanced and used unbalanced outs? (just my curiosity )

Rob

 

[dhaen]

DCX2496 reduces the output if it sees the input come in at the reduced unbalanced "home audio" level

He he, so does a piece of wire

Pro level varies throughout the world
Here its operating level is 0dB (0.774v), across the pond it's 4dB higher. Peaks can be be between 14dB and 20dB above that.
How's your maths?....

 

[SpeakerBob]

"""How's your maths?...."""

At this time of night John, terrible

If it's of help here,

analog input:

max input level +22dBu
input impedance approx 20kohm @ 1kHz

analog outputs:

max output +22dBu
output impedance approx 160ohm@ 1kHz


Does the digital input stop at 0dB ? (peak)

Cheers

Rob

 

[herm]

Rob;

I have unbalanced inputs and outputs and am hooked up:

Source > Preamp > DCX > Amp

I used this spreadsheeet to calculate resistor values for output
attenuation.

http://www.tnt-audio.com/clinica/diyattenuation.xls

Knowing a 47k ohm input impedance for my Carver amps, I will
use a 34.8k ohm in series, and a 15.4k in parallel. Resistors are on
order - I haven't implemented it yet.

As it is, the preamp must be turned up all the way see any
lights on the DCX. Maybe the unbalanced recognition thing is
working, but it doesn't seem to do enough.

Another possibility: Maybe I have no clue what the hell I am doing!

herm

 

[SpeakerBob]

Hi Herm,

I'm going to buy a meridian digital pre soon, so will be feeding the ultracurve, then dcx digitally. Hopefully a -20dB signal from a dvd setup disc will make the ultracurve show a -20 level in it's display. If it doesn't I'll have to adjust the input level.

Then I'll just calibrate the output with the vol. pots on my amps to give 85 dB at the listening position.

I'm waiting for an spl meter to turn up so i can measure my present listening levels ( it all falls between -25dB and -35dB on my present amp so I seem to have a 10 dB 'window'. I'll set it to the loudest level, measure -20 pink noise, and set the new setup the same vol.

I hope I'm making sense here...
Rob

 

[moving_electron]

It would appear that there is an input gain ajustment. Looks like the input button gets you to that?

 

[pinkmouse]

Rob

You might want to think about tweeking your pre for a bit more gain, or adding another gain stage to get the input signal up to pro levels. This will give you a much lower noise floor in the DCX processing.

 

[SpeakerBob]

Hi Al,

I'll be using a digital pre soon, so am not too worried about the analog ins at the mo. (they'll have to make do a few weeks is all)

Was more concerned about getting the outputs matched properly to home gear.

Cheers

Rob

edit: the ultracurve has a 'max' switch on the back which changes max level from +12 to +22 dBu

 

[SpeakerBob]

Thought I'd post an update....

I ended up buying a behringer 'ultra di d120' direct injection box for the time being - means my pre amp can produce the right levels for the balanced inputs of the ultracurve pro. This is routed to the dcx via aes/ebu xlr.


Of interest to people using the dcx, I used the xlr outputs with pin 3 shorted to pin 1 (ground), and pin 2 positive on a phono, with the phono ground going to pin 1.

It worked perfect with integrated amps - could possibly be more problematic with 'power amps' (with no gain/attenuation)

Tonights listening impressions (with no room eq from the ultracurve - ie flat but in the loop)- ooh and a few glasses of wine.. shows that the dcx performs way better than my yamaha av receiver (rxv-800) for x-over duties. - a lot more clarity shone through.


Hopefully when I buy my meridian 561 for pre-amp duties I will see even more clarity, but i was very surprised tonight by how clean this xo sounds.

I tried crossing at 200 from sub units to mid/highs, and 80Hz aswell - so easy to play about.

I'm running trueRTA on a different pc so i can see any changes instantly.

Will be putting my proper mid/tweets in this week for testing. - will report soon..


As a final note, I'd like to say that anybody who's thinking about trying the dcx, don't be put off by the negative comments you'll find on this forum - A lot are posted by people who haven't heard it.

To give an idea of my stuff, I'm using 2 x audiolab 8000a's for the bass (2x scanspeak8565-01's 10") per side, and a cyrus1 with b&w dm602's for mid/highs

My proper mid/ tweets are scanspeak 8545 revelators, with the revelator tweeter too... when I get the boxes finished....


Cheers,

Rob