Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th December 2012, 06:44 PM   #3391
diyAudio Member
 
Join Date: Jul 2008
Location: santa clara, CA
I plan to find out if those stupid tin cans ARE needed

its not clear. I've been thru the data sheet many times and its still not obvious if they are needed for all functions. I guess I'll remove them and it will be easy to see first-hand.

I like the idea of small coax connectors on the board. the little ones you find for GPS antennas (many kinds) would be perfect. they have all the specs we would need, and beyond. that covers the new pcb but it does not solve the tap-points problem.

one idea could be to have a small board sit right on the behringer and provide a break-out, like my hot melt glue idea, but better and more proper. small wires that go from the behringer to the breakout, then you could have the SMA coax connectors go from there. ideally, it would be great to just buy pre-made thin rf coax cables and just use them.

for the real pc, yes, I would do 3 chips. no reason not to. on my perf, I didn't need to do 3x the work (lol) and space was tight as it was. on a green board, though, I'd absolutely include all 3 pairs of channels.

I do tend to like wolfson chips, but the cirrus does not NEED (or want) any xtal boxes. and for diy, the cirrus parts are easier to solder, too.
__________________
My Photostream:http://www.flickr.com/photos/linux-works/
  Reply With Quote
Old 13th December 2012, 06:50 PM   #3392
oettle is offline oettle  Germany
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally Posted by mhelin View Post
Good point, though I guess there are reasons why 3V3 is used. Maybe it has been made it possible to regulate the power lines a little bit better. The schematics don't show it but BOM does, there is a LDO type TPS70851 3.3V/1.8V regulator on board. The ADSP-21065L anyway is a 3.3V device so it doesn't matter in fact.
The used 3.3V devices all need a 3.3V supply. So the 3.3V supply is correct. The problem is that the used devices are all 3.3V devices which need and generate 3.3V I/O signals which is incompatible with 5V devices on the DCX DSP board. For correct operation a 3.3 to 5V converter for all I/O signals would be needed.
  Reply With Quote
Old 13th December 2012, 07:17 PM   #3393
diyAudio Member
 
Join Date: Apr 2003
Location: Tampere Finland Europe
Quote:
Originally Posted by oettle View Post
The used 3.3V devices all need a 3.3V supply. So the 3.3V supply is correct. The problem is that the used devices are all 3.3V devices which need and generate 3.3V I/O signals which is incompatible with 5V devices on the DCX DSP board. For correct operation a 3.3 to 5V converter for all I/O signals would be needed.
No devices in digital audio signal path are 5V devices, all are 3.3V. The DSP and the converters all use 3.3V supplies, only the analog parts of the A/D and D/A converters use 5V (for better SNR). See Behringer Diagrams, Schematics and Service Manuals for FREE

E: Is it possible older revisions of DCX2496 were using 5V supplies? Got to check mine some day.

E(2): Seems the 5V supplied 8420 on DCX outputs SDOUT via a voltage divider (220ohm/+330ohms), other signals directly to 3.3V chips.

Last edited by mhelin; 13th December 2012 at 07:38 PM.
  Reply With Quote
Old 13th December 2012, 07:45 PM   #3394
oettle is offline oettle  Germany
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally Posted by mhelin View Post
No devices in digital audio signal path are 5V devices, all are 3.3V. The DSP and the converters all use 3.3V supplies, only the analog parts of the A/D and D/A converters use 5V (for better SNR). See Behringer Diagrams, Schematics and Service Manuals for FREE

E: Is it possible older revisions of DCX2496 were using 5V supplies? Got to check mine some day.

E(2): Seems the 5V supplied 8420 on DCX outputs SDOUT via a voltage divider (220ohm/+330ohms), other signals directly to 3.3V chips.
I wished you were right. There is only one version of DCX and there all relevant devices (IC 1, 19 (VIO), 20, ...) use 5V. Have a closer look at page 2 and 3.
  Reply With Quote
Old 13th December 2012, 10:29 PM   #3395
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Quote:
Originally Posted by oettle View Post
I wished you were right. There is only one version of DCX and there all relevant devices (IC 1, 19 (VIO), 20, ...) use 5V. Have a closer look at page 2 and 3.
Does anyone have any information on exactly what IC19 does? It's a Quick Logic QL3004 but I can't seem to find any data on it.

It looks like either a level translator or some sort of re-clocking or switch interface.

All digital I2S paths run into and out of this IC before making their way to the I2S inputs on the SHARC DSP.

The SHARC datasheet specifically mentions that it supports direct I2S connection to any I2S standard ADC or DAC, so has anyone tried bypassing the entire front and back end, sending input directly to and output directly from the SHARC DSP? This could allow bypassing all on-board clocks and digital circuitry with the exception of the 30MHz clock for the DSP itself.

I might try it with my Amanero USB-I2S board this evening on the input side... that would allow a nice USB connection directly on the back of the DCX-2496 for digital input, which runs directly into the SHARC. No need for on-board ASRC, clocks, etc...

Cheers,
Owen
  Reply With Quote
Old 14th December 2012, 12:37 AM   #3396
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
why not remove the DSP as well? at this point is there really any point at all using DCX over a small computer running software or hardware accelerated XO?
  Reply With Quote
Old 14th December 2012, 12:54 AM   #3397
diyAudio Member
 
Join Date: Feb 2009
Location: Brisbane, Australia
Quote:
Originally Posted by qusp View Post
why not remove the DSP as well? at this point is there really any point at all using DCX over a small computer running software or hardware accelerated XO?
When you want multichannel for home theatre where source may not always be the computer. Small computer with ability to switch between analogue input and software sources as well as 8 to 12 analogue outputs is well down the price per performance scale in my opinion. Why 12? 3 way left/centre/right speakers, LFE channel, rear speakers ...

Even 6 channel of dacs and a good stereo adc for a 2 speaker stereo system is a significant investment for a system that might be used for a prototype and untested speaker system.

Basically if I was to do a computer setup I'd be either using a really cheap mulitchannel adc/dac at least through the prototype phase, even fully built it is a cumbersome environment and has a learning curve associated with it that if installed in a living space with significant other and family members using the same space it has constraints that they may not be willing to live with.

Meanwhile the guy using a DSP platform has things working Good Enough TM
  Reply With Quote
Old 14th December 2012, 12:58 AM   #3398
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
I guess you havent been following the conversation, by this point after Owen's mod (and to a degree linuxworks) above, the DSP is the only thing left running in the case, no dacs, no ADCs, no clocks, no analogue outputs.

thus my comment.

also pretty sure both of them already have ADCs, DACs and Amps covered

Last edited by qusp; 14th December 2012 at 01:02 AM.
  Reply With Quote
Old 14th December 2012, 01:04 AM   #3399
diyAudio Member
 
Join Date: Feb 2009
Location: Brisbane, Australia
Ahhhh, gotcha!
  Reply With Quote
Old 14th December 2012, 01:06 AM   #3400
opc is offline opc  Canada
diyAudio Member
 
opc's Avatar
 
Join Date: Oct 2004
Location: Ottawa, Ontario, Canada
Quote:
Originally Posted by qusp View Post
why not remove the DSP as well? at this point is there really any point at all using DCX over a small computer running software or hardware accelerated XO?
I considered that... starting from scratch with just the SHARC DSP and an ESS DAC and ADC would be ideal, but the value of the finished chassis and polished user interface of the Behringer would be tough to beat.

I really love the fact that the Behringer is self contained, and isn't tethered to a PC. You can swap between a digital source or analog inputs, and the UI is really top notch once you know how to use it.

The only problem is that it sounds like absolute rubbish, and I don't say that lightly. Most of Behringer's stuff does fall into the "good enough" category, but unfortunately the DCX2496 does not. There is obscene levels of noise when using the AES/EBU digital input, and there's something about the sound that really grates on my nerves. It seems to measure acceptably well, but it certainly doesn't sound that way.

I've got a project going where I actually need mine to work properly and sound good, so I'm finally looking into what I can do about it.

Step 1 will be the PSU, then step 2 is the digital input (to alleviate the AES/EBU noise issue). Step 3 will either be a digital output scheme, or an internal ESS9018 DAC in multi-channel mode.

Before I go down that path though, I want to know if IC19 is doing something horrible to the clocks. If it is, then it will have to be bypassed, but the solder points on the SHARC DSP are not very pleasant to try and tie into

Cheers,
Owen
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 11:27 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2