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continuous-play DAC

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John Larkin

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Apr 2, 2012, 4:15:45 PM4/2/12
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Hi,

We have a customer who has a mess of digitized data from some sort of
aircraft system, and wants to play it back into some box for testing.
It will be 2 channels of 16-bit data originally sampled at about 500
KHz, several hours worth. They want us to design a VME module with
dacs and a huge amount of DRAM to store the data. We don't really want
to do it - they only need a couple of boards - but we don't like to
say no to these guys either.

So, couldn't he just use a small-box PC and a sound card? How fast can
a high-end sound card output points? The CD standard was 44KHz, but I
think there are 4x versions at least. Depending on his analog
bandwidth requirements, 196K might work.

Can a fast sound card accept data at the 4x (or whatever) rate, or
does it always accept 44K data and interpolate?

Who makes good high-end sound cards?

Thanks

John



--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

Tim Wescott

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Apr 2, 2012, 4:22:47 PM4/2/12
to
On Mon, 02 Apr 2012 13:15:45 -0700, John Larkin wrote:

> Hi,
>
> We have a customer who has a mess of digitized data from some sort of
> aircraft system, and wants to play it back into some box for testing. It
> will be 2 channels of 16-bit data originally sampled at about 500 KHz,
> several hours worth. They want us to design a VME module with dacs and a
> huge amount of DRAM to store the data. We don't really want to do it -
> they only need a couple of boards - but we don't like to say no to these
> guys either.
>
> So, couldn't he just use a small-box PC and a sound card? How fast can a
> high-end sound card output points? The CD standard was 44KHz, but I
> think there are 4x versions at least. Depending on his analog bandwidth
> requirements, 196K might work.
>
> Can a fast sound card accept data at the 4x (or whatever) rate, or does
> it always accept 44K data and interpolate?
>
> Who makes good high-end sound cards?

If you want to do this with the least muss and fuss, your best off-the-
shelf solution is probably something from National Instruments or DAQ.

I'm just guessing -- but I'd look there first.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Nico Coesel

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Apr 2, 2012, 5:02:51 PM4/2/12
to
John Larkin <jla...@highlandtechnology.com> wrote:

>
>
>Hi,
>
>We have a customer who has a mess of digitized data from some sort of
>aircraft system, and wants to play it back into some box for testing.
>It will be 2 channels of 16-bit data originally sampled at about 500
>KHz, several hours worth. They want us to design a VME module with
>dacs and a huge amount of DRAM to store the data. We don't really want
>to do it - they only need a couple of boards - but we don't like to
>say no to these guys either.

500kHz, 16 bits and 2 channels adds up to 4MB/s. I'd go for an SD card
and an NXP ARM controller. Use an SPI DAC and use the SPI timing to
get the sample rate right. Piece of cake :-)

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------

Martin Riddle

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Apr 2, 2012, 11:36:48 PM4/2/12
to

"John Larkin" <jla...@highlandtechnology.com> wrote in message
news:al1kn7h5afo6aross...@4ax.com...
>
>
> Hi,
>
> We have a customer who has a mess of digitized data from some sort of
> aircraft system, and wants to play it back into some box for testing.
> It will be 2 channels of 16-bit data originally sampled at about 500
> KHz, several hours worth. They want us to design a VME module with
> dacs and a huge amount of DRAM to store the data. We don't really want
> to do it - they only need a couple of boards - but we don't like to
> say no to these guys either.
>
> So, couldn't he just use a small-box PC and a sound card? How fast can
> a high-end sound card output points? The CD standard was 44KHz, but I
> think there are 4x versions at least. Depending on his analog
> bandwidth requirements, 196K might work.
>
> Can a fast sound card accept data at the 4x (or whatever) rate, or
> does it always accept 44K data and interpolate?
>
> Who makes good high-end sound cards?
>
> Thanks
>
> John
>
>
>
> --
>

Direct Stream digital recording is interesting....
<https://en.wikipedia.org/wiki/Direct_Stream_Digital>

pretty cheap recorder...
<http://www.bhphotovideo.com/c/product/461177-REG/Tascam_DV_RA1000HD_DV_RA1000HD_High_Definition_CD_DVD_.html>



Uwe Hercksen

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Apr 3, 2012, 3:47:32 AM4/3/12
to


John Larkin schrieb:
>
> Hi,
>
> We have a customer who has a mess of digitized data from some sort of
> aircraft system, and wants to play it back into some box for testing.
> It will be 2 channels of 16-bit data originally sampled at about 500
> KHz, several hours worth. They want us to design a VME module with
> dacs and a huge amount of DRAM to store the data. We don't really want
> to do it - they only need a couple of boards - but we don't like to
> say no to these guys either.
>
> So, couldn't he just use a small-box PC and a sound card? How fast can
> a high-end sound card output points? The CD standard was 44KHz, but I
> think there are 4x versions at least. Depending on his analog
> bandwidth requirements, 196K might work.

Hello,

5 hours with 500 kHz sampling rate, 2 channels with 2 bytes each will
need about 36 GB of RAM. So look for a small-box PC with 40 GB of RAM
and 64 bit adressing. Or a disk with more than 2 MB per second data
rate, sustained for hours.

Bye

lang...@fonz.dk

unread,
Apr 3, 2012, 8:29:05 AM4/3/12
to
you don't need all that ram, most PCs will play HD video just fine so
bandwidth
from disk shouldn't be an issue

I wonder if you could graft an SD card onto one of your arbitrary
waveform generators
it is basically spi so it not that many pins and if the data on it is
just a big flat
file it shouldn't be that hard to read from an FPGA

or maybe something like this:http://apple.clickandbuild.com/cnb/shop/
ftdichip?productID=161&op=catalogue-product_info-
null&prodCategoryID=121

-Lasse

bitrex

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Apr 3, 2012, 12:04:07 PM4/3/12
to
On 4/2/2012 4:15 PM, John Larkin wrote:
>
>
> Hi,
>
> We have a customer who has a mess of digitized data from some sort of
> aircraft system, and wants to play it back into some box for testing.
> It will be 2 channels of 16-bit data originally sampled at about 500
> KHz, several hours worth. They want us to design a VME module with
> dacs and a huge amount of DRAM to store the data. We don't really want
> to do it - they only need a couple of boards - but we don't like to
> say no to these guys either.
>
> So, couldn't he just use a small-box PC and a sound card? How fast can
> a high-end sound card output points? The CD standard was 44KHz, but I
> think there are 4x versions at least. Depending on his analog
> bandwidth requirements, 196K might work.
>
> Can a fast sound card accept data at the 4x (or whatever) rate, or
> does it always accept 44K data and interpolate?
>
> Who makes good high-end sound cards?
>
> Thanks
>
> John
>
>
>

24 bit 192kHz sample rate soundcards are commodity hardware these days:

http://www.musiciansfriend.com/pro-audio/m-audio-audiophile-192-pci-interface/703610000000000?src=3WWRWXGB&ZYXSEM=0&gclid=CLv-xNyGma8CFYNo4AodPC6x0g

among many others.

They can playback 192kHz sample rate files, no interpolation needed.

Ralph Barone

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Apr 4, 2012, 12:45:03 AM4/4/12
to
I wouldn't bet much on the analog output of this being flat up to 90-odd
kHz.

josephkk

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Apr 9, 2012, 11:11:38 PM4/9/12
to
On Tue, 03 Apr 2012 12:04:07 -0400, bitrex <bit...@de.lete.earthlink.net>
wrote:
And that ain't half the incoming sample rate. 500 ksps. Playing with a
small disk and an arb sounds like the way to go.

?-)
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