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Old 6th August 2002, 11:54 PM   #1
tiroth is offline tiroth  United States
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Default AD1853 ASRC/DAC boards FS?

As certain people are aware, I've been working on a DAC for some time. I've come to a crossroads, as I've found a way to (somewhat) reasonably have some boards manufactured. To do this economically, I'd have to modularize the design a bit. The question is, is it worth it? Would anyone be interested in the boards?

Some details:

192kHz upsampling via AD1896
192kHz DAC, AD1853
TI DIR1703 FIFO reciever IC
AD8561 or LT1016 input comparator
Analog attenuation via relays and fixed resistors (optional)
Regulators onboard for each IC
Very generous allowances for bypassing
No routing through groundplane

This board is very SMT-intensive; it had to be for best quality. The boards would be professionally manufactured 2-layer throughhole plated with SMOBC soldermask.

I will be publishing I/V outlines, but not having boards manufactured.

I'm thinking $30 for the boards, less if I end up with some definites by the time I place an order. Anyone interested?
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Old 7th August 2002, 12:09 AM   #2
BrianGT is offline BrianGT  United States
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Can you post a schematic and board layout pictures? It sounds like an interesting project.

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Old 7th August 2002, 01:32 AM   #3
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I'm always game to whip out the soldering iron...

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Old 7th August 2002, 03:08 AM   #4
tiroth is offline tiroth  United States
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You can find some schematics on my site:

http://www.anidian.com/audio/construct/adac_1.shtml

I am afraid these are a bit out of date, because it was getting to be a bear to keep the site up to date and finish the board at the same time. A boardshot from last week is below; the actual DAC/ASRC block is on the left with the S/PDIF reciever below. The "public consumption" design will be simplified, as I expect few will require 6 channels or an ADAT reciever.

If there is enough interest to order boards, I'll make the design a bit modular so it can accomadate 2-6 channels, or alternatively paralleled DACs. After all, I want multichannel even if no one else does. ^_^

Simplified boards will probably be 5"x5", with DAC module cutoffs that are considerably smaller.
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Old 7th August 2002, 08:34 AM   #5
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Can you elaborate on the specifications of the ADAT receiver? The reason I am asking is that plenty computers offer ADAT out (if you need say 8 channels), but very few offer 4 ea S/PDIF.

I am looking to take a number of channels of ADAT from a computer and outputting to DAC's

P
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Old 7th August 2002, 11:27 AM   #6
tiroth is offline tiroth  United States
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I am using Alesis' AL1402 "OptoRec" but planned to drive it electrically rather than optically. (for lower jitter)

It supports 8 channels of 24 bit/48kHz audio, and is compatible with ADAT Type I and II.

You can check out this chip on http://www.alesis-semi.com/
It is very easy to interface, plus it is SOIC.
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Old 7th August 2002, 04:40 PM   #7
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Default Anyone interested?

I believe I am interested too. I already have most of those chips just waiting to be used. It looks like very worthwhile project
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Old 7th August 2002, 05:06 PM   #8
tiroth is offline tiroth  United States
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Ok. It looks like there is some potential interest so I will take the plunge. I'll keep the forum updated. Thanks for your responses.
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Old 12th August 2002, 03:50 AM   #9
tiroth is offline tiroth  United States
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Default getting there

Well, the new board isn't routed 100%, but it is pretty close. I did some things to make it more flexible, like support for
  • axial (standard) or radial (MK132) resistors in the IREF control
  • single, one-at-a-time, or R2R attenuator (32 steps)
  • full or half size master clock
  • enough room to mount discrete master clock or small OXCO
  • add-on DAC boards
  • alternative inputs
The add-on DACs will be cutoff boards consisting of AD1896, AD1853, and the relays only. These boards can be used to increase the number of channels or improve the S/N ratio. There are clock outputs for 2 additional DAC boards. Three could probably be done by doubling up one of the 74HC04 outputs.

I'll be posting the updated schematics to my site monday or tuesday. Now is the time if anyone has input on the design.
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Old 12th August 2002, 03:52 AM   #10
tiroth is offline tiroth  United States
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Here is a shot of the ground plane. Please ignore the trace cutting across the DAC...this will probably end up being the only jumper on the board, so it won't interrupt the groundplane.

I've added some guard traces on the topside around analog sections or where the inharmonic clock is routed.
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