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Old 24th March 2004, 09:06 PM   #1
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Default dcx2496 xlr-phono advice

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
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Old 24th March 2004, 09:18 PM   #2
dhaen is offline dhaen  Europe
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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.
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Old 24th March 2004, 09:26 PM   #3
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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.
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Old 24th March 2004, 09:33 PM   #4
dhaen is offline dhaen  Europe
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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....
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Old 24th March 2004, 09:37 PM   #5
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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
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Old 24th March 2004, 09:45 PM   #6
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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?

Quote:
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.
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Old 24th March 2004, 09:52 PM   #7
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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
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Old 24th March 2004, 10:00 PM   #8
dhaen is offline dhaen  Europe
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Quote:
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?....
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Old 24th March 2004, 10:25 PM   #9
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"""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
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Old 24th March 2004, 10:27 PM   #10
herm is offline herm  United States
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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
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