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Alien DAC v1.1 Construction Thread - Page 48

post #706 of 1560
4/26/07 at 9:33am
The PCM2702 checks out okay. I'm going to scrap this board and start over. In the time I've spent troubleshooting this one I could have completed another. I've learned a lot - now I'll apply it to a new build.

Thanks again for everyone's assistance.
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post #707 of 1560
4/26/07 at 2:16pm
Has anyone made an amp-powered alien dac yet? I'd like to put one in my work SOHA so I don't have a seperate dac and cables cluttering my desk.

Quote:
Amp powered. Connect the amp’s V+ to the AV+ pad, amp’s V- to the AV- pad, and amp’s ground to the AG pad.
Will this work with the +-15V in the SOHA?
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post #708 of 1560
4/26/07 at 2:29pm
No. If you read through the design and examine the regulators datasheet you'll see that they can onlly handle up to 10v. you could work something out to drop the voltage outof you soha, but I would say that the best solution is to either use a tread connected to the transformer's output or use USB power. I have tried external power and usb power and couldn't find a difference. Furthermore, I was speaking with AMB this weekend at the international meet and he told me that he could not measure a differencebetween both using his highquality measure equipment.

IMO, go for USB powered, the simplest and cheapest solution. Use the money on some blackgate HIGH Q- Nx caps, those really make a difference.
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post #709 of 1560
4/26/07 at 3:10pm
Quote:
Originally Posted by MASantos View Post
No. If you read through the design and examine the regulators datasheet you'll see that they can onlly handle up to 10v. you could work something out to drop the voltage outof you soha, but I would say that the best solution is to either use a tread connected to the transformer's output or use USB power. I have tried external power and usb power and couldn't find a difference. Furthermore, I was speaking with AMB this weekend at the international meet and he told me that he could not measure a differencebetween both using his highquality measure equipment.

IMO, go for USB powered, the simplest and cheapest solution. Use the money on some blackgate HIGH Q- Nx caps, those really make a difference.
Yeah, that's what I was afraid of, I knew the voltage limit on the regulators from making the wall-powered one, but wasn't sure what exactly IC4 (the buffer) did to drop voltage.

The main reason I was thinking amp-powered over usb-powered is the ports on my laptop don't always provide enough voltage for the analog side to function right.
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post #710 of 1560
4/26/07 at 3:21pm
Quote:
The main reason I was thinking amp-powered over usb-powered is the ports on my laptop don't always provide enough voltage for the analog side to function right.
Are you really suggesting the USB ports on your laptop are not compliant with the appropriate USB specifications?
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post #711 of 1560
4/26/07 at 4:50pm
Quote:
Originally Posted by MisterX View Post
Are you really suggesting the USB ports on your laptop are not compliant with the appropriate USB specifications?
I had a unregulated usb alien with my cheapo Acer and never have a single problem. I am building a regulated one next, but I am pretty sure there will be no difference, or at least any major.

I measured quite stable 4.9-5.0 volts with my DMM.
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post #712 of 1560
4/26/07 at 5:07pm
Quote:
Originally Posted by Yen View Post
I had a unregulated usb alien with my cheapo Acer and never have a single problem. I am building a regulated one next, but I am pretty sure there will be no difference, or at least any major.

I measured quite stable 4.9-5.0 volts with my DMM.
Quote:
Originally Posted by MisterX View Post
Are you really suggesting the USB ports on your laptop are not compliant with the appropriate USB specifications?
Yeah, I should note that it is a regulated USB configuration. I think the problem is more that the voltage dips slightly enough to mess up the output of the adjustable regulator than anything else, this particular Alien DAC has worked perfectly on my laptop at home, my media pc, and most of the time on my work laptop. I know with the regulators there is some amount of voltage required over the output voltage and it might just be that it is acting screwy because of that.

Occasionally, I'll plug it in, it detects, but audio comes out distorted for about 2 or 3 seconds before dropping out entirely. Usually it takes a couple tries to plug it in before it works fine. The problem doesn't occur with my wall-powered one.

I should probably just try to lower the output voltage of the reguator, but I really don't want to pay shipping for 1 smd resistor
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post #713 of 1560
4/26/07 at 5:36pm
Yeah, even first class shipping for a single resistor is kinda silly.
What value do you need?
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post #714 of 1560
4/30/07 at 11:37pm
I just wanted to chime in with a success story here. People obviously post more regarding the problems as opposed to the successes, which sort of skews things I think! I purchased the AlienDAC kit from jrossel, and plan on integrating it with a B22.

First time working with SMD components. I made lots of solder bridges on the PCM2702, but they were readily fixed using some solder braid. I had access to a stereomicroscope (7X-75X mag) at work, which allowed me to identify several cold solder joints, and a bridge.
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post #715 of 1560
5/1/07 at 9:28pm

Second time's a charm

I received my new kit from Glass Jar today. I sat down to work at 3:30 and unplugged the soldering iron at 5:30 - connected power and it tested perfectly at 4.75V and 3.3V. Once plugged in to the PC it was recognized immediately. Here's a shot of it sitting on top of my Pimeta. It sounds great.

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post #716 of 1560
5/1/07 at 10:21pm
Quote:
Originally Posted by btrancho View Post
I received my new kit from Glass Jar today. I sat down to work at 3:30 and unplugged the soldering iron at 5:30 - connected power and it tested perfectly at 4.75V and 3.3V. Once plugged in to the PC it was recognized immediately. Here's a shot of it sitting on top of my Pimeta. It sounds great.
Nice job! Was this your first SMD project?
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post #717 of 1560
5/1/07 at 11:10pm
It's my second attempt at the Alien DAC (see my previous post(s)). Surprisingly, the PCM2702 and the ICs gave me no trouble. I messed up the first with lousy de-soldering technique.
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post #718 of 1560
5/2/07 at 12:13am
Quote:
Originally Posted by MisterX View Post
Yeah, even first class shipping for a single resistor is kinda silly.
What value do you need?
I'm not sure, actually, I have to double check what I actually used on it and see if I can calculate a better value. I've kind of put fixing this on the back burner, I've still got a SOHA to case up and may is pretty much completely booked for me. Heck, by the time I figure out what I need, I'll probably have jumped on another project to order parts for anyways
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post #719 of 1560
5/4/07 at 4:56pm
Can anyone tell me if IC2 is connected to C22 (on top)? They are so close and I bridged them but was not sure if this is an issue. It's going to be a pain to create that mm of separation.

Thanks.
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post #720 of 1560
5/4/07 at 5:12pm
Quote:
Originally Posted by sygyzy View Post
Can anyone tell me if IC2 is connected to C22 (on top)? They are so close and I bridged them but was not sure if this is an issue. It's going to be a pain to create that mm of separation.

Thanks.
Good idea to have the board photo handy
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