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-   -   DCX2496 Level Problem...how to confirm (http://www.diyaudio.com/forums/digital-line-level/64570-dcx2496-level-problem-how-confirm.html)

ultrachrome 19th September 2005 07:37 PM

DCX2496 Level Problem...how to confirm
 
My DCX recently seems to be providing different levels on the outs when they are set to the same value differing by as much as 6dB. For example output when 5 and 6 (my left and right tweeter outputs) are set to 0dB, one plays louder.

I've done several tests to eliminate drivers, cables, amps and preamps but how can I test the DCX on the bench and verify with DMM?

Has anyone RMA'd their DCX?

DIY_newbie 19th September 2005 08:15 PM

UC,

Why are you using 5/6 as your tweeter outputs? I'm using 3/6 as per the default configuration. Using pinknoise for my DEQ I see all paired outputs 1/4, 2/5, 3/6 to have the same relative level when set to 0db. Do you have access to pink noise generator?

--Chris

ultrachrome 19th September 2005 08:34 PM

While trying to isolate the problem I switched from the default 1,2,3 / 4,5,6 to 1,3,5 / 2,4,6. This only helped to suggest that the issue pertains to specific output channels and not the DCX configuration.

I can get pink, white, sine, triangle, square, etc. from TrueRTA.

If I were to guess I would think I would turn off all filters and crossovers for all channels and set all input and output levels to 0.

Then I would input a sine wave at maybe 1k and measure the output by using my DMM on pins 1-2 and then 1-3 which should provide the same value. I'm not really certain how to measure that, VAC on my DMM?

Then I'd repeat this for each channel and for a handful of other frequencies.

Madmike2 19th September 2005 08:37 PM

Why dont you hook up a Mic and let the auto setup function take care of all the annoying stuff :D ?

Madmike2 19th September 2005 08:39 PM

DIYNewbie ..... i see you have a DEQ along with your DCX .. does it daisy chain and control the crossover with the serial link ? I want to buy one hook it all up and let it auto level my room THEN play with it ... is that a possibility ? Have you done anything similar ?:confused:

ultrachrome 19th September 2005 08:46 PM

Quote:

Originally posted by Madmike2
Why dont you hook up a Mic and let the auto setup function take care of all the annoying stuff :D ?
I don't believe the DCX has that kind of auto setup. It just does that for time alignnment. Maybe you are confusing it with the DEQX?

I've unbound the channels so I can adjust each one individually and get both speakers measuring the same but I went to a lot trouble to build a fixed attenuator for each channel so I could run with all my levels at 0dB.

DIY_newbie 19th September 2005 09:07 PM

Quote:

Originally posted by Madmike2
DIYNewbie ..... i see you have a DEQ along with your DCX .. does it daisy chain and control the crossover with the serial link ? I want to buy one hook it all up and let it auto level my room THEN play with it ... is that a possibility ? Have you done anything similar ?:confused:
I have not tried anything like this.. The problem is that the DCX has a rs232 control port, wheras the DEQ's port is MIDI..

The method I used is as follows :

1) set cross over points for each speaker on DCX
2) check polarity with DCX auto-align function selecting only the "polarity" option.
3) time align drivers with DCX auto-align function selecting only the "short delay" option.
4) run auto EQ function on the DEQ to equalize the room response (be sure not to set below the roll off of the speakers or you'll en up with a really nasty boost on the bottom which degrades the sound.

I'm connecting mine Digital into the DEQ, Digital between DEX and DCX which IMHO adds the least amount of noise...

Hope This Helps

--Chris

johnnyx 19th September 2005 09:48 PM

The outputs are balanced; are you using them balanced or single ended?

If you are using them single ended, and one channel has the unused output connected to ground, but the other channel has it left floating, then there will be a difference in level.

Just a thought, but it's an easy fix if that is your problem :)

ultrachrome 19th September 2005 10:48 PM

I currently have them setup as detailed in this thread: Setting up active speakers...


In an earlier thread I posted the schematic of what I am using:
http://www.diyaudio.com/forums/attac...amp=1125518341

It's accurate with the exception that I excluded the toggle switches for level adjustment and polarity selection.

Davey 19th September 2005 11:47 PM

All you need for a source is a signal generator or sinewave test tone from a test CD of some sort. Any frequency will do.
Program your DCX as a direct feedthrough with no processing on all six channels. Use your DMM set to read AC volts and take some readings.

Your external output configuration schematic looks fine. It's configured to attenuate 6db on both the + and - outputs and it's not connecting pin 1 to pin 3 (which is good.)

All six channels should read exactly the same measuring between pin 2 or 3 to ground (pin 1.) If they don't then you've got some kind of internal hardware problem.

Cheers,

Davey.


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