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Alien DAC v1.1 Construction Thread - Page 20

post #286 of 1560
8/28/06 at 4:55pm
You specified a limit of 20-30 and i didn't knew if i can "play" with
bigger inductors...i thought that there can be even a small difference...

Alf if you have spare time....me and some other guys have trouble understanding some things! please try to expain us what's going on
with the "crystal loading capacitors" from what i know they keep the
frequency steady... is this the reason they exist?
I ordered some FOX crystals which they say CL=20pF i suppose i must use the nearest caps i can find (22pF) to drive them...correct? or i should use the ones you say in your site?! i have read some things about "frequency pull"
so i guess not?
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post #287 of 1560
8/28/06 at 5:16pm
The loading capacitors set the time required to start up the oscillator and then maintain it within it's spec. There's a ramp up time defined by Cl and the crystals specs until it becomes stable. This is important in devices where you can't gaurentee the start up response. You can slightly tweak the frequency of the x-tal using them, but not by very much. The PCM2702 defines the frequency as "12MHz +- 500ppm", and I doubt you'll ever pull it out of that range unless you use values well out of range. Just get the nearest easily available value
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post #288 of 1560
8/28/06 at 8:56pm
Cr@p

I found REG10*UA-A LDO is out of stock at Digikey now.
Not able to complete my order due to that.

Any alternative chips?

Analong Device has LDO chip that has similar spec tho, I can not be sure it is compatible with or not. Any idea?
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post #289 of 1560
8/28/06 at 9:02pm
Quote:
Originally Posted by Seaside
Cr@p

I found REG10*UA-A LDO is out of stock at Digikey now.
Not able to complete my order due to that.
You sure about that? Digikey tells me that they have 300+ of the REG101UA-A in stock right now.

Hope that helps.

Nate
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post #290 of 1560
8/28/06 at 9:56pm
Oops... Sorry, I must be confused of something.
Thanks, I ordered mine.
But it looks like REG10* chips are going short pretty fast.
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post #291 of 1560
8/29/06 at 2:03am
Yeah well I wanted reg102ua-a but that's not been in stock at digikey for quite some time and TI has no stock either. They'll have 4000 in early october, TI that is. Digikey is estimating late october they'll have them in.

So looks like reg101 it is.
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post #292 of 1560
8/29/06 at 3:30pm
Okay this is my last annoying Alien DAC related question.

For the LED a low current one is specified. Is it critical you use one,I can't see why, or is it just suggested ?

From what I've gathered it shouldn't be a problem, even with the reg101, is it just that you don't want to draw too much current off the USB ?

I'm assuming it would be fine running an LED on 20mA.
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post #293 of 1560
8/29/06 at 4:09pm
20mA is a lot for an LED, it'll be annoyingly bright. I've got a blue one in mine down at about 1.5mA and it's plenty bright enough.
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post #294 of 1560
8/29/06 at 4:50pm
Really ?

I thought around 15 - 20mA was typical for most LEDs.

Wonder what I've been smoking.
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post #295 of 1560
8/29/06 at 4:56pm
Quote:
Originally Posted by splaz
Wonder what I've been smoking.
Resistors?
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post #296 of 1560
8/29/06 at 5:56pm
Nice one Nate,
I have most of my LEDs running at 7mA, and they're bright enough. Check out the luminosity VS forward current plots for the LEDs you'll be using (they're usually referenced from 20mA)
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post #297 of 1560
8/29/06 at 10:39pm
Ack,
I just realized that I ordered the REG101UA-5 correctly, but the incorrect 3.3V regulator. I got REG102UA-33 instead of 101.
Does it matter if it's mismatched, or is it recommended to have the same type?
I can easily whip up a quick order from DigiKey, but if it's not necessary then much the better.
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post #298 of 1560
8/29/06 at 11:21pm
It seems that splaz is not the only one been smoking resistors here.

Quote:
Does it matter if it's mismatched
Not really.


REG101= 100mA
REG102= 250mA
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post #299 of 1560
8/30/06 at 2:25pm
I hope my post is in the correct place...

i want to try Elna RFS (cilmic II) for my alien dac...
47µF 6.3V Radial.

I can't get them localy or from online store...so if someone has spare
please find a way to comunicate with me!
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post #300 of 1560
8/30/06 at 9:48pm
digikey has 47uf 25v which there is just enough room for.
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