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Old 5th January 2005, 06:30 PM   #251
AR2 is offline AR2  United States
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Quote:
Originally posted by ergo

I have installed a Tent XO2 to DCX and thus the I2S is clocked out from CS8420 according to this "master clock".
I have heard the effect as my own setup uses a clock feedback to Sony CD player.
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I am planning of doing the same thing - ordering clock from Tent (based on Ergo's pdf instructions ), but I have some Questions - is it possible to use that clock as a master clock. My missunderstanding is: SRC and DEQ 2496 both acccept world clock, yet DCX 2496 doesn't. Is it because clock has to be where the A/D/A conversion takes place?
If that is the case would it be possible to install BNC plug in the back of DCX and distribute that to DEQ and CD player?
AR2
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Old 5th January 2005, 08:06 PM   #252
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Quote:
Originally posted by AR2
If that is the case would it be possible to install BNC plug in the back of DCX and distribute that to DEQ and CD player?
AR2
Yes, I guess this should be no problem. I suggest The SCR and the DEQ both accept WORD-Clock. This can be easily taken from within the DCX2496 and send it on an BNC. And you are right! The master clock should be where the D/A converter is hosted.
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Old 5th January 2005, 09:34 PM   #253
ergo is offline ergo  Estonia
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Here is the link to my "work in progess" web page

Ergo's DIY site

I have so little time to make it that the info might rotten before I get done So I publish what I've got.

Ergo
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Old 5th January 2005, 10:09 PM   #254
AR2 is offline AR2  United States
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Thank you guys for the prompt answers.
Is there limit how many units coud be sinked with XO as master clock? I am acctualy thinking on CD and DEQ which is two units in addition to DCX.
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Old 9th January 2005, 03:04 PM   #255
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Quote:
Originally posted by AR2
Is there limit how many units coud be sinked with XO as master clock? I am acctualy thinking on CD and DEQ which is two units in addition to DCX.
As far as I know there shall be no limit. Just plug a BNC T-connector on each device you like to connect to the clock and wire them together like a bus. The last open end you have to terminate with a 75 Ohm terminator.
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Old 22nd January 2005, 02:32 PM   #256
Lyckman is offline Lyckman  Sweden
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Cool comprehensive DCX mod

Hi guys!

My first post here. Been lurking for quite some time though, and it's about time I made one
I also posted this in the Yahoo group DCX 2496, but I'll probably reach more people here.

I'm working on the designs for a comprehensive mod of the DCX. I have two DCX's in my HT system, hooked in at exactly the wrong place (between preamp and poweramp, and no volume control after the DCX).

I want to modify both DCX's to take i2s directly in an all input channels. I'll mod a cheap DD/DTS receiver to get L/R/LS/RS/C/Sub serial i2s data out.
I'm thinking of using one of the Panasonix XR-xx for this, and take the signal right before the PWM output stage.

For the output of the Behringer, I will take the analog signal right of the DACs after adding series resistor and a polypropolene kondensator at each channel (4,7uF should be sufficient according to my calculations). I will feed the (total of 12 channels) to six motorized and IR-controlled stereo ALPS 10k log pots for the meantime. Might replace them with attuntators (how do I spell that?!) later on.

I've only looked at the input of the Behringer so far. I thought I might share what have found out to "test" the design with you guys.

Input channel A/B. The 8420 Sample Rate Converter is setup to run in hardware mode 1. This needs to be changed to hardware mode 2 (to support I2S instead of AES/EBU). This is achieved by connecting pin 20 to + instead of ground. AES/EBU connection will be removed from pin 4 and 5. Pin 4 is wired to + and pin 5 to ground to enable Serial I/O Format “2” (which is I2S). Serial data from the panasonic receiver will be wired to pin 12,13,14. Please let me know if I’m missing something or if I’m completely wrong.

Channel C is harder. No sample rate converter to hook in to. Now the ADC handles the output sample rate. The Shark expects the signal to be 24/96, so I guess the only thing to do is to add an other 8420 and set it up as above? Should do the trick, right? (Expensive little suckers, though).
  • Facts:
  • All datasheets of DD/DTS decoders that I have looked at, has one “shared” i2s stream for sub and center channels.
  • The analog input on DCX channel C is connected to both input L and R of the 5383 ADC in parallel. In conclusion, the output data stream wich feeds the shark has identical (hopefully) left and right channels.
  • Questions:
  • Does the behringer DSP software for some kinky reason expect a “dual-mono” I2S signal from channel C?
  • If No, Does it only use data from one of the channels? (Would be the best for me, but why oh why did they have to connect the ADC in the way they did.. got me puzzled.)
    (I don’t really expect anyone to know the answers to above questions )

If only one channel is used in the Shark. How do I flip the L/R in the I2s data stream in able to route the sub channel to one DCX and the center channel to the other? Can I just invert ILRCK (eg use a 74HC04) to achieve that?

If both channels are used, I’ll need to create a “dual mono” signal. Anyone has any ideas for that?

In any case, I’ll have to do something in the DD/DTS receiver in able to get four wires out of it. The Center/Sub stream must be “copied” somehow, or is it possible to feed two sources with the same wires of an i2s datastream? Maybe I should implement the “dual-mono” logic there. Ideas for components appreciated.

Does anyone know how far one can wire i2s signals without having to use a tranciever?

// Lyckman
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Old 22nd January 2005, 02:46 PM   #257
EC8010 is offline EC8010  United Kingdom
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Welcome to the forum, Lyckman. I wish everyone's first post was as good as yours!

As to your I2S question, the further they go, the more skew there will be between signals due to cable capacitance, and that will be translated into distortion. I've recently been investigating RS485 tranceivers (for my Behringer) and have been deeply unimpressed by the waveform attainable at the far end of a 3m piece of cable. And my tests were intended to check the characteristic impedance of the cable - not the quality of the tranceiver! I'm intending to use a current feedback video op-amp from the EL2030 family with a gain of 2 to drive the cable from the cable's characteristic impedance, then terminate the far end of the cable with the same impedance. That should ensure correct edges at the far end.

Don't forget that you can configure a Behringer to pick up only the A (or B) channel from an AES3 signal in order to use it as a six-channel crossover. You then need two Behringers and an AES3 distribution amplifier to feed them.
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Old 22nd January 2005, 05:39 PM   #258
Lyckman is offline Lyckman  Sweden
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Ok. 3m is way longer than I was aiming for. More like 30cm or so It would be nice if I could "be without" transievers.

I've Never heard of an AES3 distrubution amplifier, but by the name of it, it should most likely contain the circuitry I'll need for the i2s distribution. I'll do a little research on this. At least it is somewhere to start. Thanks.

// Lyckman
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Old 28th January 2005, 07:47 AM   #259
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I think you will like it. I have been using one in a 4way configuration for over 6 months now, but a couple of words of advice (which probably other members have already made);

i) You need to get the input level up, not only to avoid quantising noise, but to ensure that you get the stop-band rejection you expect from the crossover.

ii) I found that the auto delay feature on mine does not perform correctly. I can measure the impulse response of each driver/DCX channel and calculate the time of flight from the driver to the microphone, but in each channel the time delay is different -despite running the auto delay feature.

Anyway, if you have an MLS program like Soundeasy you can adjust the delays manually, to time-align drivers. Also it seems like the time delay is dependant upon the processing power of the DSP. chage the filter slope, them the delay changes as well.

Enjoy the Behringer, amazing value for money...
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Old 28th January 2005, 09:16 PM   #260
mige0 is offline mige0  Austria
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Default cheap trick

hello

when removing the analog i/o board for checking the under side, i found the sound improved a lot after reassembling without having done anything at all.

my guess on that is, that the cabel from x1 to x13, carrying the audio signals don't like to be glued down to the metal, but benefit from having some 1-2 cm air isolation witch might lower capacitence to ground.


greetings
michael
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