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Alien DAC v1.1 Construction Thread - Page 16

post #226 of 1560
8/17/06 at 4:30pm
Quote:
Originally Posted by deadlierchair
Alright, all of that is understood. I checked those two pins to see if there were any bridges but couldn't find anything. At this point I'm wondering if there are bad connections elsewhere on the board, if I soldered on an incorrect part, or if I possibly killed the PCM2702 with all that heat. I tried to get some better pictures but only had a little bit of luck.
All components appear to be soldered correctly. You are most likely to have a short on 5V after IC3. It is either PCM2702 pins on the analog/right side or the SMD capacitors on the same side. I would triple check those (check under the pins too). Any other location is less likely. Anyway I suggest to clean the board and make sure that there is no traces of solder and flux anywhere on the board.

If all this does not help, find a thin screwdriver or a needle and clean/scratch between PCM2702 pins and tiny traces around it. If this does not help either, well, I am afraid it would be about time to start working on another board.
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post #227 of 1560
8/17/06 at 4:35pm
Quote:
Originally Posted by splaz
Well got on the 2nd group buy and am sourcing parts.

For CL/CR. Two caps that I can actually get for that are

Nichicon FG 47uF

or

Elna Starget 22uF

either of them worth considering ?
If you cannot get hi-end electrolytics, go for larger film capacitors. Low-end electrolytics may sound nasty. You would be wasting your money and effort using those.
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post #228 of 1560
8/17/06 at 6:25pm
I'm about to purchase all the parts for (4) Alien DACs. What would be the best quality cap for CL/CR with a reasonable price at digikey or mouser? I'm considering buying Averovox AFPS caps since they're a good price and got good ratings from http://ecp.cc/cap-notes.html.
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post #229 of 1560
8/17/06 at 6:56pm
Quote:
Originally Posted by abcheng
What would be the best quality cap for CL/CR with a reasonable price at digikey or mouser?
Elna RFS series from Digikey
To be more specific Part number #604-1054
problem is they are a little to big around to fit flat on the board.
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post #230 of 1560
8/17/06 at 7:09pm
Quote:
Originally Posted by MisterX
Elna RFS series from Digikey
To be more specific Part number #604-1054
problem is they are a little to big around to fit flat on the board.
Thanks for the response . I'll definitely give those a try.
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post #231 of 1560
8/17/06 at 7:34pm
If you want to try the Silmic II's (RFS) part 604-1052-ND fits perfectly into CL/CR, but is only 22uF.
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post #232 of 1560
8/17/06 at 11:26pm
I said pics would follow "soon", I guess i procrastinated a bit, so here it is finally.






The RCA jacks will be replaced by something nicer when I get around to case it up , probably, hah.

Not bad for 1st time smd eh? The white stuff is residue from cleaning with 99% isopropynol, any way to clean it properly? I was under the impression 99% would be pure enough not to leave residue, or is that residue flux that was dissolved by the alcohol but not cleaned off the board completely?
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post #233 of 1560
8/17/06 at 11:45pm
Quote:
Originally Posted by Fiola
Not bad for 1st time smd eh?
Not bad at all.




Quote:
or is that residue flux that was dissolved by the alcohol but not cleaned off the board completely?
Yup... that residue is the flux.
If you are using just alcohol and an old tooth brush you will have to clean it a couple of times to get that all off.
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post #234 of 1560
8/18/06 at 3:33am
Hey guys, all crystals require the leads to be soldered (duh :P), i know that. But what about the outer casing and the pads?

Rob.
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post #235 of 1560
8/18/06 at 4:00am
where are you planning on soldering the case and or pads to?

And while I am at it...

Why do you think you sometimes see the can (or case as you call it) soldered to board?
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post #236 of 1560
8/18/06 at 4:14am
Okay, sorry, may i rephrase my question?

The PCB has pads around where the can (now that i know thats the word ) should be. On some PCB's ive seen it soldered. What is its purpose?

Rob.
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post #237 of 1560
8/18/06 at 4:37am
They do that for vibration and shock control.
Tall parts don't always play nice when shipped half way around the world and that is one solution you commonly see companies use to ensure they do.
Ever wonder why you see glue all over large capacitors in retail gear?
Same thing.
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post #238 of 1560
8/18/06 at 4:50am
Ohh... interesting, i didnt know that. I take it the reason that there are pads for crystals but not other tall/er parts is because they have metal cans and thus it makes sense?

[edit]: Also, is the improvement in overvolting the PCM2702 to 5.4v going to be noticable? Or better yet - to what extent do you think it might be noticable?

I see that the SNR raises a few dB, nothing to be writting home about. The THD, however, goes from .002 to .0015.... whats a .0005 difference like? (Jees, when you write it like that it doesnt seem like much)

Rob.
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post #239 of 1560
8/18/06 at 5:36am
Quote:
Originally Posted by MisterX
They do that for vibration and shock control.
Tall parts don't always play nice when shipped half way around the world and that is one solution you commonly see companies use to ensure they do.
Ever wonder why you see glue all over large capacitors in retail gear?
Same thing.
It also can dampen a circuit and improve sonic performance in some cases. This is especially noticable on speaker crossovers -- coat them in epoxy (or even better, take them out of the speakers and put them in thier own little boxes) and you will notice that the sound gets better. There are even some film caps that you can hook to a multimeter and watch the capacitance change as you squeeze them. This also happens as the air pressure in the speaker changes altering the crossover's filter points.
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post #240 of 1560
8/18/06 at 8:54am
Hi all,

I've built up my first (of 5) of these, and whilst it appears to work fine I get a lot of very audible noise - which almost sounds kinda looped?

The variant I've built is fed by a 9v battery and feeds the PCM chip 3.3v and 5.6v ( stuffed up my order of smt resistors and omited the K on the end of one of the values ) so had to use the next closest match I had.

I've used the 1A variety of the 1206 SMT Murata ferrite, but had to sub-out the 600R for the red LED for about 60R.

Other than that I'm using all std R values, and std C values for the smt capacitors. The electrolytics I'm using are: 470uf x1, 100uf x2, 47uf x1 and CR and CL are 10uf - all Nichicon FX.

The Crystal is this guy:
Digi-Key Part NumberX983-ND
Manufacturer Part NumberECS-120-32-1X
DescriptionCRYSTAL 12.000MHZ 32PF HC-49/UA

Help?
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