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Alien DAC v1.1 Construction Thread - Page 79

post #1171 of 1560
4/30/08 at 2:06am
i've sent him like a week ago. he replied 2 days later to ask whether i need anything else.. but nothing from him after i reply.

update: i just received an email for jeff. He's waiting for parts from mouser and delivery would be this saturday
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post #1172 of 1560
5/2/08 at 11:32am
Quote:
Originally Posted by bhjazz View Post
Currently Digikey is out of the Panasonic 100uF. Backordered until May 13th or something crazy like that.
Simply as an FYI, I received an email for Digikey:

"The backorder will ship automatically once it becomes available. We show
approximately 13/May/08."
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post #1173 of 1560
5/9/08 at 7:51pm
I got the kit from glassjar audio several days ago. After soldering everything, the the chip doesnt output right audio signal. i tried to tap directly from the chip for both left and right output. I can hear the left output but not the right one. so is this because my chip is faulty?

thanks in advance
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post #1174 of 1560
5/9/08 at 8:35pm
Quote:
Originally Posted by NumpXP View Post
I got the kit from glassjar audio several days ago. After soldering everything, the the chip doesnt output right audio signal. i tried to tap directly from the chip for both left and right output. I can hear the left output but not the right one. so is this because my chip is faulty?

thanks in advance
Probably not the chip. Lets back up a second...

This is an Alien DAC kit from Jeff at GlassJar? Did it have the PCM chip pre-soldered? Or did you solder it on?

Its most likely a solder bridge, or something not soldered on enough (bad phrase, but whatever). These boards seem to take a bit to get somethings soldered on and making contact. A joint may look fine but isn't. If it is the right channel, take a DMM (meter) and in ohms mode, ohm the riight audio channel out from the DAC on. Make sure that you check the actual physical pin on the chip to the pad or board trace to ensure that it has continuity. There isn't alot to it--OUTL or OUTR to the coupling cap to the jack.
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post #1175 of 1560
5/15/08 at 4:55pm
I was looking at the pdf for the PCM2702, specifically to see if there was a location to connect for a lock indicator. I know, splitting hairs since this will come from USB. Will this DAC just "work or not work"? I think we've all experienced that blast of white noise from a non-locked signal, and I'd like to save my headamp or headphones (or ears!).

(incidentally, I recently blew the fuse on my Classe amp by sending a non-locked blast of digital noise from my Theta preamp. Scared the crap outta me!)

Just tossing this out for discussion...
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post #1176 of 1560
5/15/08 at 9:40pm
I get the dreaded white noise from my Alien occasionally (usually after playing for a while). Any way to check and see of it is an Alien problem or a computer problem? If it is the Alien , what are some commom casues of this problem?
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post #1177 of 1560
5/15/08 at 9:59pm
Also, I do get 3.3V when usb powered and 4.7V. Is the 4.7V too low?
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post #1178 of 1560
5/15/08 at 10:32pm
Hard to say on the 4.7V Vcc thing. The datasheet minimum for the chip is 4.5V. The voltage of the REG101A is controlled by the ratio of R31/R32

Vout = (1 + R31 / R32) * Vref, where Vref is 1.267 for REG101

Stock values are supposed to be 31.2K and 11.5K... you could do something like put a 100K in parallel with R32, which would give you about 10.3K so your output voltage would be 5.1V. Soldering SMD resistors on top of one another isn't too hard to do. The 3.3V controls the digital section of the chip; I wonder if the white noise you mention is digital (lock or whatever) or analog in nature?
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post #1179 of 1560
5/15/08 at 10:41pm
Quote:
Originally Posted by rhester View Post
I get the dreaded white noise from my Alien occasionally (usually after playing for a while). Any way to check and see of it is an Alien problem or a computer problem? If it is the Alien , what are some commom casues of this problem?
This sporadically occurs for me too, although I think it happens only on WinXP, not Linux. Re-plugging the USB connector usually clears it up. I think it might be a problem in the Windows USB audio driver.

Not everything is peachy on Linux either, though. Sometimes if I start a song using SoftSqueeze it gets all scratchy and distorted sounding, but stopping and restarting the song "fixes" it. I think this might be a SoftSqueeze issue, because it also happens with the M-Audio Transit USB sound card, but not when I use a different player software.
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post #1180 of 1560
5/15/08 at 10:49pm
I wondered if it my be a Windows problem (running XP), but don't get the nosie when I go USB out to another pro usb dac. But it will usually clear up for a while if I replug or restart the music app.
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post #1181 of 1560
5/17/08 at 12:41am
No takers on the lock indicator? Okie dokie, then. Personally, I think it would stand out more in the specs if it really were avilable anyway.

While reading the spec for the chip, I did come across something interesting about the reset-ability of the chip. Page 9 says, "...THe PCM2702 includes an internal power-on reset circuit which automatically initializes digital logic when Vdd exceeds 2.0V typical (range 1.6V to 2.4V)." I'm wondering if this has somethign to do with the sporadic white noise and the ability to pull and replug the USB cable. If so, it makes pretty good sense, although I'm not sure why the voltage on USB would swing high like that. I mean, it's not like it's analog, right?
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post #1182 of 1560
5/17/08 at 12:52am
Quote:
Originally Posted by bhjazz View Post
No takers on the lock indicator? Okie dokie, then. Personally, I think it would stand out more in the specs if it really were avilable anyway.

While reading the spec for the chip, I did come across something interesting about the reset-ability of the chip. Page 9 says, "...THe PCM2702 includes an internal power-on reset circuit which automatically initializes digital logic when Vdd exceeds 2.0V typical (range 1.6V to 2.4V)." I'm wondering if this has somethign to do with the sporadic white noise and the ability to pull and replug the USB cable. If so, it makes pretty good sense, although I'm not sure why the voltage on USB would swing high like that. I mean, it's not like it's analog, right?
Considering that there is no such thing as a "lock" in terms of the receiver chips, you don't have to worry. The chip acts as a USB host (sound card) and sends the signal to itself (only supporting 44.1kHz or 48kHz), so it never has to "lock" with another component.
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post #1183 of 1560
5/17/08 at 12:57am
That makes perfect sense. Cool. Thanks! I'll reserve my questions about general lock issues for another thread.
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post #1184 of 1560
5/18/08 at 6:10am
Quote:
Originally Posted by bhjazz View Post
That makes perfect sense. Cool. Thanks! I'll reserve my questions about general lock issues for another thread.
PCM2702 does offer two outputs that are somewhat analogous to a 'lock' indicator.

/SSPND (pin 11) will go low when the device is successfully attached to a USB bus. This could be useful if you're self-powering the DAC. /PLYBCK (10) goes low when audio data is being played.
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post #1185 of 1560
5/18/08 at 9:48pm

Alien DAC Problem - Only 1.23v out of 3V3

I've just put together a Glass Jar kit, USB powered . I'm only getting about 1.23vdc from the 3V3. I get a rock solid 4.7vdc on the 5V.

Yes, it's my first surface mount with pitches like the 2702! I've checked my solder joints as well as I know how (they look good - to me - ) but is there something I'm missing?

Anyone know of anything specific I might check? Thanks all for any help!

-Bill

(I'm working on some pics of the board if it might be helpful.)
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