Alien DAC v1.1 Construction Thread - Page 12

So, I got one soldered up nice, windows detects it, but I have absolutely no sound coming out. Time to read through this thread and do some troubleshooting.

While there is no reason to suspect it over something else - check for bridges with your soldering, especially on the output resistors.

Rob.

Thank you Alf!

You're right i sould read your support site first...

after reading the site, i have a problem and a question!
my question is why the REG101UA-33/REG102UA-33 are Mandatory!?
i understand that it regulates the voltage to 3.3V but why is that? as far as i know we need much more to operate the PCM2702 (sorry but i'm lost reading the threads and now i'm maybe asking the obvious)


visiting mouser kai digikey for first time in my life, i got terrified!!!
do i need to pay 36E for tranportation costs, etc for buying things of 4-5E total price? i feel like i live in Mars and they gonna send them to me with Spacecraft!

Please answer because it is important for my decision to participate to
the group buy...

Im not totally sure, but i think that each of those solder contacts on the ferrites are connected together, not as in they are seperate ferrites. Kind of like this:

whiz: The PCM2702 requries a 3.3v power supply for its "digital side" and a 5v power supply for its "analogue" side. The board comes with provisions for the use of TI's REG10* regulators, but you do not have to use them if you dont want to. Two diy-LM317 power supplies (a la TREAD) would suffice, although would require more work on your part.

As for mouser and digikey shipping - yes, its very expensive. You have a couple of options here:

1) Call in a favour from a fellow head-fi'er. Ask that, if you can get the money to them, if they can order your parts for you in an order they are already doing - and then forward them on to you.

2) Find somewhere locally (or closer at least) that offers the parts you are after.

Rob.

All my soldering looks ok, but I think I figured it out: my 3.3v pad reads right on, 3.3 exactly, but the 5v pad reads .04 Looks like I screwed something up with the adjustable regulator. I have no idea what, though. Maybe I'll swap it for the normal 5v regulator (I was going to try for usb powered but decided not to).

Edit: Ok. reg101ua-5 is now on there. Same problem. 3.3v reading is fine, 5v reading is next to nothing. The regulator is getting REALLY hot. There don't appear to be solder bridges anywhere, looking under a large magnifier. I am puzzled and a bit annoyed.

Again, I'm hardly an expert here, but i would bet that there is either a solder bridge or the PCM2702 in stuffed (overheating? I dont know if that would cause it).

Does your multimeter have a continuity function?

Rob.

I had this problem and it was from a bridge on the dac chip, I looked and looked but did not find anything but untill I reflowed the solder on the dac did it clear up the problem. The 3.3v rail was fine but the the 5.0v rail was shorted someware.

Yeah, I've got a continuity check. I'd spent about a half hour to an hour trying to get the dac chip done right, I thought I had it but maybe I missed something.

If there is a solder bridge anywhere, its there. I've checked over EVERY other component with a magnifier. But the +5 line is shorted to G somewhere.

Hold the board against bright light while checking it with magnifier.

That REALLY helped. I held the thing right up to a 120 watt bulb - could see the teeniest little solder bridge.

It works! Time to let it break in.

Are boards still available? Can I get a couple?

Second group buy.

C2 Recommendation?

Can someone recommend a part from Digikey or Mouser for C2 that is in stock. I'm trying to place an order for parts for 2 DACs based on the BOMs I have seen, but the options suggested for C2 are unavailable.

Thanks,
Garron

Here are some that would fit the specs:

Panasonic ECG 470uF (P1158-ND) or NHG 1000 uF (P5521-ND)

Nichicon PW 1000 uF (493-1747-ND) or VZ 1000 uF (493-1270-ND)

United Chemi SMG 1000 uF (565-1024-ND)

These are all 10V rated. I noticed that Digi-key also has some Elna caps at higher rated voltages. You may want to check those out.

Regarding regulator options

I know this has been asked more than a few times, but I gotta ask a few question regarding regulator thing again.
Because, it is still not very clear regardless of those answers, and I need to order parts soon when I got my boards from second group buy.

Please check and correct me if anything is wrong here.

I will use USB as a power source.
I know I still need IC2 any case, since it is mandatory for 3.3V digital input.
Questions are mostly regarding IC3.


1. Unregulated USB.
I do NOT need IC3, and registers arround it. I wil get 5V directly from the USB port.

2. Regulated USB
I will need IC3. There might be two choices, REG101UA-5 and -A?

Option1. REG101UA-5
I will get regulated 5V from this IC, ONLY when my USB port supplies a few mV more than 5V.
If my USB port works perfect, which provides 5V, the IC will not regulate since it needs a few mV more than 5V to work correctly.
In other words, the whole thing works just like the unregulated USB option. So there's no point of choosing this option.

Option2. REG101UA-A
I will need to find out the right value of register R31, and R32 to get regulated voltage of approx 4.6~4.8V from the IC3.
The voltage out will be (1+R31/R32)*Vref, where Vref is 1.26 for REG101 and 1.267 for REG102.
(Alf's support site states this value as 1.1267, so is it 1.267 or 1.1267?)

Here's some question regarding this option.

A. Does input voltage from USB port(Vusb) has to do anything with the regulated voltage(Vout)?

B. If the answer above is "Yes", Am i need to aim at Vout 0.4V less than Vusb?

C. Assume the answer above is "No. It doesn't matter as long as it is close to 5V" then, Can I choose values of R31 and R32 to make Vout approx 5.3V in order to over-drive the DAC?
For example, R31=33K, R32=10.5K, then Vout will be approx 5.3V. Is this possible?

Thank you very much.