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Alien DAC v1.1 Construction Thread - Page 71

post #1051 of 1560
3/1/08 at 2:36pm
Initially, I'd just look over the board to see if all the solder points look good, ie, they all seem soldered properly to the board, and that there are no bridges and stuff. Since it works for the most, everything is probably in the right place.. does it work after a break? 7 days isn't a nominal working time..
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post #1052 of 1560
3/1/08 at 3:19pm
Quote:
Originally Posted by ruZZ.il View Post
Initially, I'd just look over the board to see if all the solder points look good, ie, they all seem soldered properly to the board, and that there are no bridges and stuff. Since it works for the most, everything is probably in the right place.. does it work after a break? 7 days isn't a nominal working time..
I should have noted that I bought the DAC used off of him- so he's been running it for who knows how long and when I got it, everything worked for- I don't know- a month? Then one day I just get distortion. It sounds like the signal is getting through but on a very weak connection.

The caps are most prone to being moved around but I guess I should be looking to make sure all connections are good. (wish I had a voltmeter).

Do you think a bad ground from the RCA connectors could have caused distortion? I was fiddling around with those before and if the ground hoop thing wasn't making good contact with the female end, then maybe it could be the culprit... I will test that theory later today.
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post #1053 of 1560
3/1/08 at 3:53pm
Quote:
Originally Posted by xnothingpoetic View Post
I should have noted that I bought the DAC used off of him- so he's been running it for who knows how long and when I got it, everything worked for- I don't know- a month? Then one day I just get distortion. It sounds like the signal is getting through but on a very weak connection.

The caps are most prone to being moved around but I guess I should be looking to make sure all connections are good. (wish I had a voltmeter).

Do you think a bad ground from the RCA connectors could have caused distortion? I was fiddling around with those before and if the ground hoop thing wasn't making good contact with the female end, then maybe it could be the culprit... I will test that theory later today.
Yep - you'll get some wild buzzing/crackling if that ground lead is only making intermittent contact. If that's not it, then check the solder connections on those output caps. If things are loose and move, the solder joint could come loose.

Sounds like it's that ground connection, though.
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post #1054 of 1560
3/1/08 at 4:15pm
hey im just wondering, how will this little dac compare to that of a beresford dac, music fidelity x-dac or the zero dac? I have just bought a second hand millet amp and im wondering if it will be of any use t me? I already have the three dacs i mentioned so am i wasting my time with the alien dac?
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post #1055 of 1560
3/1/08 at 10:58pm
I'm redoing an Alien DAC for another head-fi'er and ran into a potential problem: I needed to transfer all of the components from an existing board to a new board. One of the caps (C11) came apart when I was desoldering it. This appears to be from a jrossel kit, and I had initially thought it was 33pf, but now think it is a 20pf COG ceramic, 0805 pkg. If I try to fire this thing up with this missing, I presume it should still work? Or not? I can probably grab a 0805 20pf from a lab at work, but getting a COG may be a problem...
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post #1056 of 1560
3/1/08 at 11:06pm
I would bet on it not functioning properly with that cap.
(without the load capacitance there is nothing there to "control" the crystal's resonant frequency)
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post #1057 of 1560
3/1/08 at 11:07pm
Quote:
7 days isn't a nominal working time..
How do you figure that?
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post #1058 of 1560
3/2/08 at 4:30am
unscientifically
I guess just not much IME, which is limited anyway.
Ultimately, if the thing works, I guess it shouldn't have a problem working long but I suspect in such a time frame there are things that could throw it off, specially if something small is wrong.. some contact that changes with the temp. or something. Though if anything is seriously wrong, I doubt it would play for the first 7 days to begin with. Just speculating, and I'd like to eventually learn what the culprit is after all, if any.
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post #1059 of 1560
3/3/08 at 2:22am
Quote:
Originally Posted by Pars View Post
I'm redoing an Alien DAC for another head-fi'er and ran into a potential problem: I needed to transfer all of the components from an existing board to a new board. One of the caps (C11) came apart when I was desoldering it. This appears to be from a jrossel kit, and I had initially thought it was 33pf, but now think it is a 20pf COG ceramic, 0805 pkg. If I try to fire this thing up with this missing, I presume it should still work? Or not? I can probably grab a 0805 20pf from a lab at work, but getting a COG may be a problem...
I know, bad form to quote myself.

It worked without the cap (at least the computer saw it as a valid USB device). Next problem: 3.3V test point was fine but 5V test point was reading about 1.5V. After going thru this thread (searches), I found one reference to the resistors (R31/R32) being reversed. Checked those, that wasn't the problem. Another reference to the ground (pin 4) on the +5V vreg not making contact... checked that with a meter to the pin of the chip and ground... that was fine. I removed both R31 and R32, made sure of their values, and reinstalled them. Same problem.

Then, I ohmed out ground to the ground side of R32 and it was reading 40k or more. Heated this joint up alot more, and now ohming it out gave <1 ohm to ground. DAC works fine now.

So what the one poster was saying about the coating on the pads, particularly for ones on the ground plane, being hard to get good contact on is true. Particularly when you are using a small tip for the 0805 SMD, it is hard to heat things up enough.
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post #1060 of 1560
3/3/08 at 4:20am
Hi MisterX, I've heard that you're very good with DIY stuff, can you suggest a good parts list for the AlienDAC? I'll most likely be ordering through Digi-Key. Thanks!
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post #1061 of 1560
3/3/08 at 4:47am
http://www.glassjaraudio.com/product...=4&productId=6
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post #1062 of 1560
3/3/08 at 4:57am
I already have PCBs though.
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post #1063 of 1560
3/3/08 at 5:01am
Quote:
Originally Posted by rockbottom View Post
I already have PCBs though.
Then just use the BOM
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post #1064 of 1560
3/3/08 at 5:28am
Quote:
Originally Posted by FallenAngel View Post
Then just use the BOM
Do you remember how much does Digi-key charges to ship to Canada?
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post #1065 of 1560
3/3/08 at 5:30am
Quote:
Originally Posted by MisterX View Post
Do you remember how much does Digi-key charges to ship to Canada?
Yep, it's $8 flat-rate for Purolator 2-day express, just use Digi-Key Corporation - Canada Home Page. Best place for parts in Canada, just avoid Mouser at all costs, shipping is expensive, slow and customs sucks!
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