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Alien DAC v1.1 Construction Thread - Page 7

post #91 of 1560
7/23/06 at 8:51am
Quote:
Originally Posted by robzy
I am going to use the onboard 101/102s except use an external wallwart instead of USB power.

Rob.
The onboard regs have a max supply voltage of 10V. If you use, say, a 9V unregulated wart, you might fry em since the wart might put out 10-12 volts or more under the light load of the DAC.

You actually need a regulated supply just to protect the regulators, as strange as that sounds
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post #92 of 1560
7/23/06 at 9:31am
Quote:
Originally Posted by NeilR
The onboard regs have a max supply voltage of 10V. If you use, say, a 9V unregulated wart, you might fry em since the wart might put out 10-12 volts or more under the light load of the DAC.
Thanks for the headups, although i have already been contemplating this problem. Maybe just a big resistor between them would do it? Not overly elegant though. Could always build a 5v LM317 PSU and use that for the analogue side, and use a reg101 to do the 3.3v....

*strokes chin*

Or better yet - a diode or two before the reg101s?

Rob.
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post #93 of 1560
7/23/06 at 9:52am
Quote:
Originally Posted by robzy
Thanks for the headups, although i have already been contemplating this problem. Maybe just a big resistor between them would do it? Not overly elegant though. Could always build a 5v LM317 PSU and use that for the analogue side, and use a reg101 to do the 3.3v....

*strokes chin*

Or better yet - a diode or two before the reg101s?

Rob.
I ordered an MC7809 regulator. That's easier to implement than an adjustable regulator. If you try to do it with diodes, you may find you need more than one or two, and you have no protection from a mild power surge, say 10V on the mains, that would put another volt or so into the circuit. For 46 cents you can be done with it and not have to think about all these things.

You might want to go with an MC7808 to make sure a 9V supply (if that's what you are using) accounts for the drop out voltage. A decent rated 9V supply ought to put out 10V or more at the 50ma or so the DAC will be drawing. I went with the 7809 because my supply voltage will be 12+V to get the batteries charged.
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post #94 of 1560
7/23/06 at 3:06pm
What about using a 5-6V unregulated wallwart? It should give you <9V. Of course you have to test it first.
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post #95 of 1560
7/23/06 at 7:24pm

DAC pics

I completed my USB DAC the other day and here are a few pictures. By the way, I purchased all the caps Handmade Electronics and I had no problems at all.

I chose to regulate the USB power down to 4.8V and it works fine. The output is a little low but my preamp can correct that.
This was a really fun project and the SMD soldering was not difficult.

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post #96 of 1560
7/23/06 at 8:24pm
Whoa! Got a bit of capacitance there, don't you?

Looks good, though.
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post #97 of 1560
7/24/06 at 8:07pm

up in smoke

After I completed the second DAC the exact same way I did the first one, I was going to compare and see if I could hear a difference between a fresh on and one that had been played a wile, Broken in. I plugged my first one in and it went up in smoke. The second one is fine and working but the first one I can not believe it went like that, just out of no where? Strange. Post mortem revealed nothing wrong. I wish I ordered more boards. I really need 2 more boards.
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post #98 of 1560
7/24/06 at 9:26pm
Could the LED leads have shorted out against the USB plug case? They're right next to each other, and in your photos the LED is standing straight up on its uninsulated legs. Just a guess. Sorry about your board.
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post #99 of 1560
7/24/06 at 10:55pm
Quote:
Originally Posted by tomb
Could the LED leads have shorted out against the USB plug case? They're right next to each other, and in your photos the LED is standing straight up on its uninsulated legs. Just a guess. Sorry about your board.
good guess but not the case, Im sure I know what the problem, or short was between 26 and 27 or 25 and 26 because L18 smoked. I was sad. For it to be working an hour before it smoked.
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post #100 of 1560
7/25/06 at 1:05am

Just finished the Alien DAC

I just finished the Alien DAC (w/ 4uF ERO MKC coupling caps).

In comparison to my modified AV-710 (w/ 4uF ERO MKC coupling caps), the mids are definitely better with a forward presentation. The sound is a lot more 3D and surrounding. This is definitely worth the build.

I originally bought Silmic II 4.7uf from digikey for coupling, and after changing to MKC caps the sound changed dramatically for the better. (faster, better mids and a lot less bass bloat)

I just have a couple of concerns. I bought the wrong type of ferrites (240-2539-1-ND), so I was wondering if I installed them correctly or not.

(note my 330K resistors are air wired to my stereo jack)

Thanks for your help

My soldering job was quite bad since I currently have a 3/16" tip on my iron


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post #101 of 1560
7/25/06 at 1:31am
Quote:
Originally Posted by tomb
Could the LED leads have shorted out against the USB plug case? They're right next to each other, and in your photos the LED is standing straight up on its uninsulated legs. Just a guess. Sorry about your board.
Never mind, I resurrected my DAC from the dead, installed the PCM2702E resolved the issue though I am not sure why it acted up in the first place. Its good to have soo many parts left over, in my case enough to make a grip more DAC's
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post #102 of 1560
7/25/06 at 1:42am
Yikes, C16 looks bridged.
For the ferrets, I would conclude that that's the only way to solder those types.
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post #103 of 1560
7/25/06 at 5:39am

low output ?

Never mind. Always make sure windows volume is set to 100%
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post #104 of 1560
7/25/06 at 5:47am
did you set the system volume of your computer to 100% ? Usually it's set automatically to 50% when you connect the usb dac.
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post #105 of 1560
7/25/06 at 6:18am
Ok I didn't check volume today when I noticed low signal. But yes I did set it to 100% first time I connected the DAC to my PC. Today I connected second board (which presumably is identical for the Windows). For some strange reason as soon as I realized that windows mixer could be a problem, I connected DAC again, clicked volume icon and it was 100% already. Played some music - and this time it was as loud as my sound card or CDP. So I'm still not sure what happened, but its all good now.

On a good note - replacing Panasonics with Blackgates really improved sound. First with Panasonics I noticed that bass is not as good and tight as on Revo 5.1. Now with BG I think DAC sound is better that Revo. Need some more listening before I can tell for sure.

I've build two boards. Both for "regulated" USB power. One with 101A and default R31/R32. Which gives about 4.8V. Another one with spare 1.5K added to R32 - resulting in 4.4V. Just to check if 0.4V given in REG101UA spec really improves regulation. Both work fine... wish I had something to check and compare REG101UA outputs.
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