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Old 17th October 2012, 03:22 PM   #3341
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Default Line out vs digital in

Quote:
Originally Posted by zigzagflux View Post
That's why you go digital in, xfmr coupled out into passive attenuator with buffer. Get the most out of the fairly-well-done digital/DSP section, and maximum analog S/N. easy to do with simple mods (no board level soldering required).

IMO anything else is compromised, or adds additional complexity needlessly.

Strong vote for Jensen or Cinemag line out.xfmrs.
First of all I'm learning everyday as I've landed a DJ gig. Just bought a DCX2496 and running 2 way Peavey SP-1's (modded) and a sub, in 3 way stereo. I use a PC as source with Foobar 2000 + Wasapi (event) plugin, 0.0 db gain, (rca 75 ohm to xlr to input A ) DCX setup as AES/BEU input.After fiddle f******g with xover's and output gains, My modest amps are barely idling. Question is, you are saying that using an analog output control for master volume ie: Jan Didden's mod would be the best bet to max sound quality for a very limited budget? Regards 2S2P
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Old 17th October 2012, 04:58 PM   #3342
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Exactly. For optimal sound quality, you want to run the D/A near or at full output level (without clipping, of course). This maximizes the use of the digital bits, which is information about the sound to the D/A. If you attempt to use digital volume control or do not run input/outputs at maximum levels, you are effectively throwing bits away, which results in less information about the original sound. Also can increase s/n ratio.

Ideally, you want the hottest signal possible out of the DCX (this doesn't mean crank up the digital gain in the DSP). Your ganged analog volume control then adjusts the signal to each of your amps based on desired audible volume level.
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Old 7th December 2012, 05:46 AM   #3343
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sorry if this has already been asked (searches don't find this info).

what logic level (voltage) is i2s run at, in the dcx2496? is it 3.3v or 5v?

I'm about to try to interface some wolfson wm8805 spdif tx chips by tapping into the i2s lines on the behringer. but it would be nice to know that its already 3.3v (?)
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Old 7th December 2012, 06:27 AM   #3344
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Quote:
Originally Posted by linuxworks View Post
sorry if this has already been asked (searches don't find this info).

what logic level (voltage) is i2s run at, in the dcx2496? is it 3.3v or 5v?

I'm about to try to interface some wolfson wm8805 spdif tx chips by tapping into the i2s lines on the behringer. but it would be nice to know that its already 3.3v (?)
3.3V. The ADC and DAC in the DCX2496 all have 3.3V on their Vd pins.
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Old 7th December 2012, 07:59 AM   #3345
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Quote:
Originally Posted by linuxworks View Post
sorry if this has already been asked (searches don't find this info).

what logic level (voltage) is i2s run at, in the dcx2496? is it 3.3v or 5v?

I'm about to try to interface some wolfson wm8805 spdif tx chips by tapping into the i2s lines on the behringer. but it would be nice to know that its already 3.3v (?)
The DCX2496 is a mixed 3.3V and 5V design but the link between DSP and ADC/DACs is 3.3V only.

Is there a certain reason for converting onboard I2S to S/PDIF? This would need a sample rate conversion (SRC) and a reclocking on the destination side of the S/PDIF line similar to the digital input (CS8420) of the DCX. This will cause a decrease of sonical performance!

I'm not aware of the actual discussions. I set up a list of the available mods for the DCX two years ago. Might be that some links donít work any more but perhaps itís helpful for you.
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File Type: doc DCX table.doc (150.5 KB, 52 views)
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Old 7th December 2012, 08:49 AM   #3346
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Hello Frank,

I'd like to mention that for my active mod there is now a small optional mic input board.
The digital input XLR connector is replaced with a combined XLR and 6.3mm stereo mic connector on a small board. Ward Maas from Pilgham Audio can supply the kit.
Maybe you could update your overview accordingly:

Retains Mic input ? yes (option)

jan
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Last edited by jan.didden; 7th December 2012 at 08:51 AM.
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Old 7th December 2012, 09:18 AM   #3347
oettle is offline oettle  Germany
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Quote:
Originally Posted by jan.didden View Post
Hello Frank,

I'd like to mention that for my active mod there is now a small optional mic input board.
The digital input XLR connector is replaced with a combined XLR and 6.3mm stereo mic connector on a small board. Ward Maas from Pilgham Audio can supply the kit.
Maybe you could update your overview accordingly:

Retains Mic input ? yes (option)

jan
Hi Jan,

I updated my file according to your proposal. I asume there aren't any other new mods for the DCX available meanwhile but prices might have changed? So please look on the sites of the sellers for the latest prices.
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File Type: doc DCX table.doc (151.0 KB, 50 views)
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Old 7th December 2012, 12:15 PM   #3348
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Hi Frank.

I know you have a LOT experience with DCX. I want make USB digital input on DCX with Amanero USB to i2s USB to I2S 384Khz - DSD Converter.
I want ask Amanero to modify drivers so there will be just 96khz option /safety reason/ and resample on pc on source side /digital in "clockless" domain/. For example you can force win7 to resample all sound to 96 khz with decent quality algorithm. All dcx devices will be slaved to amanero 24.576 mhz clock. This way there will be just one physical clock domain and you omit ASRC. What do you think about such solutions? How you solutions react to jitter on source side? Is there some measurable differences between sources or are modern ASRC algorithm clever enough to suppress any problem before them?

Thank you very much for answer and thanks for all your very rational DIY DCX contributions so far.
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Old 7th December 2012, 03:30 PM   #3349
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Quote:
Originally Posted by oettle View Post
The DCX2496 is a mixed 3.3V and 5V design but the link between DSP and ADC/DACs is 3.3V only.

Is there a certain reason for converting onboard I2S to S/PDIF?
yes! I want to run my own choice of dacs as the output stage. many people prefer to mod the analog chain on the dcx's output but I'd like to go all digital and have the box just run spdif-in and spdif-outs.

I'm planning on using a chip I've already worked with, the wm8805. I've been able to hack a chip into the audio widget and that's been reliably converting i2s to spdif. my audio widget is now just a usb/spdif box at up to 24/192.

Quote:
This would need a sample rate conversion (SRC) and a reclocking on the destination side of the S/PDIF line similar to the digital input (CS8420) of the DCX. This will cause a decrease of sonical performance!
I'm not sure I follow this. no src is needed. the data is 24/96 as it hits the local set of 3 dacs onboard. all I'm doing is taking the 24/96 data and skipping the AK dacs and sending it to 2 or 3 wolfson transmitter chips.

people have done this before:

Behringer DCX2496

I think all the kits of boards that were done years ago are all sold out, so I'm going to try to revisit this idea but with 8805 chips instead of the cirrus ones.

I'm hoping I can use the 3 clocks as-is. I know lrclock and bitclock are 'fine' but I'm not 100% sure if I can just feed the onboard mclock to the wolfson. I'll find out really soon, though, before I build too much.
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Old 7th December 2012, 04:04 PM   #3350
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also, this is where someone else did the same mod as I'm planning:

DCX2496 mod for Digital OUT x 3
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