Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Alien DAC v1.1 Construction Thread
New Posts  All Forums:Forum Nav:

Alien DAC v1.1 Construction Thread - Page 94

post #1396 of 1560
8/25/08 at 3:11am
Anyone have a spare 2702 they'd be willing to sell/ship to me? I'm fairly sure mine is fried.
Reply
post #1397 of 1560
8/25/08 at 3:58am
Well, its not a wiring mistake. I was building 2 at the same time, 2nd one worked without any issues off the bat.

Problem with the first has been isolated, but not sure if its fixable. Measured OUTL and OUTR. OUTR was around 2.2v, OUTL was around 1.5 and would 'bleed' down to 0. Possible chip is fried?
Reply
post #1398 of 1560
8/25/08 at 8:03am
Quote:
Originally Posted by SmellyEagle View Post
Well, its not a wiring mistake. I was building 2 at the same time, 2nd one worked without any issues off the bat.

Problem with the first has been isolated, but not sure if its fixable. Measured OUTL and OUTR. OUTR was around 2.2v, OUTL was around 1.5 and would 'bleed' down to 0. Possible chip is fried?
It depends on your choice of wire colors. Most people use green for ground. If so, your green wire is on the Right channel, and red is Ground.

Soldering looks OK from here - very nice macro photography, too, btw.
Reply
post #1399 of 1560
8/25/08 at 9:01am
Quote:
Originally Posted by SmellyEagle View Post
Well, its not a wiring mistake. I was building 2 at the same time, 2nd one worked without any issues off the bat.

Problem with the first has been isolated, but not sure if its fixable. Measured OUTL and OUTR. OUTR was around 2.2v, OUTL was around 1.5 and would 'bleed' down to 0. Possible chip is fried?
Are you checking AC or DC? And is this without load or with load?

You could just being seeing the output capacitor loading up and starting to filter DC. When I first tested mine it took forever for the output caps to "fill" with no load, but once I out my headphone amp on the end it happened quickly.
Reply
post #1400 of 1560
8/25/08 at 1:06pm
Quote:
Originally Posted by tomb View Post
It depends on your choice of wire colors. Most people use green for ground. If so, your green wire is on the Right channel, and red is Ground.

Soldering looks OK from here - very nice macro photography, too, btw.
You know what, I think I did mess that up. I guess thats what you get for trying to finish stuff up at 2am. I hope I didnt hurt the board as I was poking around... towards the end of the night, the left channel just stopped working. Praying it was temporary.
Reply
post #1401 of 1560
8/28/08 at 12:15am
Just put together a DAC here, can't get it to power up. It's USB powered. Problem seems to be no power is getting to PCM chip. I have AV+ jumpered to +5V. I can light an LED between +5V and G but not 3v3 and G.

Of the 4 pins that connect to the USB receptacle only one will light an LED and it is not the one that runs to R13 L13||L14. Do I have a faulty USB cable perhaps?
Reply
post #1402 of 1560
8/28/08 at 12:23am
I might be wrong, but for USB power, I don't think you jumper AV+ to 5V+. Taken from myexposition:

Power supply. I will refer to the S1 pad nearest to the USB receptacle as S1a and to the other one as S1b.

* External PS or battery powered. Connect V+ to the AV+ pad and V- to the G2 pad (or S1b and G1 respectively).
* USB powered. Jumper S1a and S1b or use a SPST switch.
* USB and PS/battery powered. Use an ON-OFF-ON switch. Connect V+ to one throw, the S1a pad to the other throw, the S1b pad to the common pin, and V- to the G1 pad.
* 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.

On the previous page, I have posted pics of a successfully wired usb powered dac (well, minus OR and OG getting mixed up).
Reply
post #1403 of 1560
8/28/08 at 1:58am
He can jumper AV+ to 5+ if he wants unregulated USB power. He would not need IC3 (the REG101-A) in that case, either.
Reply
post #1404 of 1560
8/28/08 at 2:00am
Thanks for the correction
Reply
post #1405 of 1560
8/28/08 at 10:09am
If I'm not getting voltage at the 3v3 point, I'm guessing I should be looking more closely at my IC2 soldering correct?
Reply
post #1406 of 1560
8/28/08 at 10:45am
Quote:
Originally Posted by Jam_Master_J View Post
If I'm not getting voltage at the 3v3 point, I'm guessing I should be looking more closely at my IC2 soldering correct?
Yep - or the chip is bad.
Reply
post #1407 of 1560
8/29/08 at 8:38am
Quote:
Originally Posted by tomb View Post
Yep - or the chip is bad.
Thanks, I just re-flowed all my IC2 joints. DAC got picked up by Windows right away and produces nice sound, all is good
Reply
post #1408 of 1560
8/30/08 at 10:53am
Still using my alien DAC, enjoying it but wondering if this behavior is normal : sometimes, after listening to some music/ playing a game for some time, if I turn off my amp (a headsix) and have no music playing, and I can hear a slight high freq noise (using senn hd650).

It doesnt seem to last for a long time), but it kinda worries me, apparently it s a dc offset. I had tried measuring it by plugging a mini to mini ic instead of the senns in my headsix and using my DMM on the mini jack and had gotten pretty high values (2V I believe), but they decreased over time. I suppose it s the capacitors discharging

what s weird is that it doesnt always happen. But it has me a tad worried. Does such an offset risk damaging my phones?

thanks in advance for your answers
Reply
post #1409 of 1560
9/7/08 at 10:51pm
Hey all.

I'm about ready to get building my Alien DAC (been taking my time on other projects !), and have a slight conumdrum.
I want to put a buffer (Jisbos) after the DAC. Now, the buffer runs off 15V supply, while the DAC wants 5V. I'm thinking of just building a +/-15V supply, and use a resistor to drop the voltage enough for the DAC.
Thing is, I'm not sure what the current draw of this DAC is, so am not sure what value resistor I should use.

Any advice ?
I guess a last resort will be a voltage divider to "ball-park" it, and let the onboard regulator do the rest.
Reply
post #1410 of 1560
9/7/08 at 11:10pm
30mA is the max supply current specified in the PCM2702 datasheet.


to bad it's so big because otherwise Allied # 879-9999 would make for a very easy power supply for that combo.
Reply
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Alien DAC v1.1 Construction Thread