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Old 14th August 2007, 03:04 AM   #1
ghetto is offline ghetto  United States
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Default Another DAC + Headphone amp

Hi guys.

This is my first audio project, but not my first rodeo. I have taken quite a lot of influence from Gary Marsh (HD-1) and ezkcdude (ezdac). The improvements I aim to make with this project are:

- Improved power supply via low noise LT1963 regulators.
- Volume control is done via balanced programmable gain amplifiers. (Some may debate whether this is better or not.)
- PCB will be 2 layers and therefore cheaper and less of a pain to order in small quantities. (Some may prefer 4 layers for better power and ground layout schemes.)

There are some factors which will probably be considered negative:
- Since I am laying the board out in the free version of Eagle, I only have about 4"x3" and 2 layers to play with, so the transformer will not mount on the PCB... the finished DAC probably won't be quite as svelte as the HD-1.
- You will still have to program the ATmega microcontroller. They are my favorite 8 bitters so I'm sticking with them.

There are a few items that may change or be added:
- IR receiver for remote control. I plan on using this board with a power amp as well, so this would be handy.
- Encoder in place of potentiometer.
- Sub 2 x WM8816 for 2 x PGA2320.

Attached is a preliminary schematic, which I post hoping someone will catch simple mistakes that are surely there. I have not rigorously calculated the proper gains for the various portions of the design, but I will be doing that and finalizing the rest of the schematic over the coming days. Your feedback is welcomed ....
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Old 14th August 2007, 07:30 PM   #2
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Default Where to get chips

I have some small stock, the min/mult is 47 and they are $7.33 per.



Let me know what else you may need, thanks.



Rebecca Bennett

Micro Com Inc.

17502 Irvine Blvd E2

Tustin, CA 92780

Phone: 714-505-9806

Fax: 714-505-9961

www.microcom-inc.com
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Old 14th August 2007, 09:25 PM   #3
ghetto is offline ghetto  United States
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So I would have to buy 47 WM8816?
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Old 14th August 2007, 09:28 PM   #4
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ask in an email,
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Old 14th August 2007, 11:50 PM   #5
troystg is offline troystg  United States
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Quote:
Originally posted by ghetto
So I would have to buy 47 WM8816?

You design a good PCB and offer it as a GB and that might not be enough!

I would not condone it as a commercial venture, but a GB is a GREAT way to finance YOUR own personal parts and materials.

Design a product, come up with a parts list and offer them at a reasonable cost. People WILL buy a good kit priced right. Collect 1/2 to 3/4 of the money up front, order them and ship out kits. In this case it would "only" be 45-46 kits...
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Old 15th August 2007, 12:09 AM   #6
ghetto is offline ghetto  United States
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Hmm. I will think about it. The prospect of organizing a GB does not appeal much to me though...
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Old 15th August 2007, 01:14 AM   #7
troystg is offline troystg  United States
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Boards are EASY! Components are much tougher..

I'd suggest boards and chip /controller parts.. Resistors, caps and such anyone can get.. Think about just the "big" stuff, and then it would be very easy.


Maybe someone else would do the GB if you designed the kit. If your talking a GB of 4-5 items x 45 kits it is VERY easy.
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Old 15th August 2007, 01:16 AM   #8
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Hey, ghetto. Schematics are relatively easy. Designing the board - much harder IMO. Anyway, thanks for the shout out. Good luck with your project. I only have one opinion right now. I don't understand why you think the LT1963 is so great. The ripple rejection is lower than LM317, and I don't think it's less noisy either. However, low dropout has some advantages.
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Old 15th August 2007, 09:23 AM   #9
Ardee is offline Ardee  England
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Looking at the schematic, I think you will need to reference RXN on the receiver chip to ground if you want to use the optical input?
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Old 21st August 2007, 05:17 AM   #10
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Hi guys:
IMHO i would personally go for PGA coz they are easy to get compared to WM chips, though I have two lying around for which I could find no use.
Seems a nice project.
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