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Old 13th April 2015, 12:39 AM   #1
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Default Pitchfork pre-amplifier

I know I might be close to "being in over my head" ....

But that level of challenge is what keeps me going .

The design goals -

PCB 1 = analog

-Analog regulated power supplies.
-IC / discrete class A buffers.

PCB 2/3 = digital

- DAC / clock

- PGA2311 /arduino /LCD display

- of course .... the analog 3.3 , 5V digital supplies.

PS - the PCB being split will allow just a line stage builder
to also take part in the project.

(below 1/2) - the line stage.
10ppb/1k diamond based buffer - 7X gain.

Also , the .asc ...

OS
Attached Images
File Type: jpg pitchfork 1.0.jpg (117.0 KB, 1445 views)
File Type: jpg pitchfork THD.jpg (120.1 KB, 1374 views)
Attached Files
File Type: asc IC-Line-stage.asc (6.3 KB, 64 views)
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Last edited by ostripper; 13th April 2015 at 12:42 AM.
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Old 13th April 2015, 12:57 AM   #2
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This guys DAC looks neat. A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) I'm not sure if 8 paralleled stereo DAC chips are really needed though.
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Old 13th April 2015, 01:40 AM   #3
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Quote:
Originally Posted by jwilhelm View Post
This guys DAC looks neat. A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) I'm not sure if 8 paralleled stereo DAC chips are really needed though.
Unless you have other needs or idea's ....

DAC goals ...
- based on the PCMxxxx - check this out -
Texas Instruments PCM5102 Series Audio D/A Converter ICs | Mouser
32 bit next gen 1728 (bragging rights !! )

- S/pdif and toslink inputs

- low jitter clock

- DAC buffers , all the datasheets recommend a follower.

- power supplies (onboard).

I'm going to start with a "pcm1794 dac project or kit" google search.
Unless 6$ is too much .... PCM5102 , as well.
OS
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Last edited by ostripper; 13th April 2015 at 01:43 AM.
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Old 13th April 2015, 01:47 AM   #4
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I saw the 5102 but it actually doesn't look as good as the 1794. The only thing it does better is it can read 32 bit. It's at the end of it's life cycle too.

Do you want to run it NOS? I found it interesting TI was recommending a Linear buffer over their OPAs in the datasheet I was reading.

Last edited by jwilhelm; 13th April 2015 at 01:51 AM.
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Old 13th April 2015, 01:54 AM   #5
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Quote:
Originally Posted by jwilhelm View Post
I saw the 5102 but it actually doesn't look as good as the 1794. The only thing it does better is it can read 32 bit. It's at the end of it's life cycle too.

Do you want to run it NOS? I found it interesting TI was recommending a Linear buffer over their OPAs in the datasheet I was reading.
A shame , the 5102 has the I/V and output filter integrated ... 1794 does not.
Wonder what else TI has ?

OS
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Old 13th April 2015, 01:57 AM   #6
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NOS = paralleled dac's using more space and current ??

Sounds like class A (or silver wire/boutique caps) for digital ?

OS
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Old 13th April 2015, 01:59 AM   #7
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There's a 5102A to replace the 5102. TI has loads of different DACs. We better do a bunch of research here. It's looking like the 32bit stuff is their lower end lines.
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Old 13th April 2015, 02:04 AM   #8
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Originally Posted by ostripper View Post
NOS = paralleled dac's using more space and current ??

Sounds like class A (or silver wire/boutique caps) for digital ?

OS
I've seen a lot of discussion about the NOS thing but don't know much about it. Signal specs look better if they are run in mono but I don't know if it's enough that we could hear.
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Old 13th April 2015, 02:08 AM   #9
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http://www.ti.com/lit/ds/symlink/pcm1795.pdf

1795/6 have the attenuator built in ,no pga2311 needed !

But they still need the external I/V -filter.

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Old 13th April 2015, 02:10 AM   #10
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The 5102A does look easier to work with.
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