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Alien DAC v1.1 Construction Thread - Page 9

post #121 of 1560
7/26/06 at 11:08pm
New stuff from Mouser all over tonight. Looking at my catalog, it looks like August will bring with it a new edition. So, are Oscon caps supposed to be good? Is that Mouser's answer to DigiKey's Elna's?

On a different note, Kyoto-Electro apologized through a Paypal dispute process and refunded my money, since it turned out he was out of stock with those BG caps, anyway. I guess he's trying to do better. Meanwhile, my BG's from Parts ConX have been shipped.
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post #122 of 1560
7/27/06 at 12:57am
time to make a pure silver usb cable
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post #123 of 1560
7/27/06 at 1:33am
The USB cable is supplying power to the amp. And I know USB 2.0 cables have a larger gague of power wiring than USB 1.0. This might be something to look into when optimizing the power section of the amp... Another is using a powered hub with a good wall wart...
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post #124 of 1560
7/29/06 at 8:03am
I hope it's not too dumb a question but I wondered if someone could offer me a little advice re: building on of these to feed into a Gainclone amp I'm building.

My Gainclone is fed by a rather large 225VA 25VCT transformer, and I'd like have a source selector so I can use a pair of RCA style connectors and what I hope is a nice clean output from these little DACs.

It will look something like this:

Code:
RCA -> (no preamp) -> source selector ---> 50K pot -> Gainclone
                                 |
Alien DAC -----------------------/
Is any particular variant of the build more suited to this? If I feed the SMD vreg 35VDC is it going to die horribly (give it's small size and amount of power it would have to dissipate)?

Thx!
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post #125 of 1560
7/29/06 at 8:09am
Quote:
Originally Posted by raromachine
If I feed the SMD vreg 35VDC is it going to die horribly (give it's small size and amount of power it would have to dissipate)?
definitely! REG101 respectively REG102 have a max input voltage of only 10V! (way different from LM317). Feed the DAC directly from the USB line or build a dedicated psu like a TREAD.
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post #126 of 1560
7/29/06 at 8:25am
Quote:
Originally Posted by steinchen
definitely! REG101 respectively REG102 have a max input voltage of only 10V! (way different from LM317). Feed the DAC directly from the USB line or build a dedicated psu like a TREAD.
As above. You will kill reg10* with more than 10v.

Rob.
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post #127 of 1560
7/29/06 at 9:05am
Cool that's that part of the Q answered - I guess the other part is will the PCM chip feed the amp, or does it need a opamp/buffer?
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post #128 of 1560
7/29/06 at 10:08pm
I'll assume it doesn't for now

My BOM for 3 DACs (comments please):

Code:
DACPart#QtyReqdQtyToBuyDigikeyPart#DescPrice Each US$Price Total US$

ICS
IC133PCM2702E-ND  IC 16-BIT STER D/A 28-SSOP   $9.66  $28.98 
IC233REG102UA-3.3-ND IC LDO REG 3.3V 250MA 8-SOIC  $2.36  $7.08 
IC333REG102UA-A-ND IC LDO REG ADJ 250MA 8-SOIC  $2.36  $7.08 

Ferrites
L11-L182430490-1057-1-ND FERRITE CHIP 600 OHM 1500MA 1206 (higher current, same size) $0.20  $6.00 

Capacitors
C1310587-1442-1-ND CAP CER 4.7UF 10V X7R 0805  $0.28  $2.81 
C233Nichicon MUSE FX 470UF 50V ( from http://shop.diyrealaudio.com/ in Taiwan? )
C11, C12610PCC330CGCT-ND CAP 33PF 50V CERM CHIP 0805 SMD  $0.05  $0.49 
C1333Nichicon MUSE FX 47UF 50V ( from http://shop.diyrealaudio.com/ in Taiwan? )
C14-C19,C21,C22,C31,C323040PCC1812CT-ND CAP .1UF 16V CERAMIC X7R 0805  $0.07  $2.96 
C23,C3366Nichicon MUSE FX 100UF 50V ( from http://shop.diyrealaudio.com/ in Taiwan? )
CL, CR66Nichicon MUSE FX 4.7UF 50V ( from http://shop.diyrealaudio.com/ in Taiwan? )

Resistors
R11,R12610311-22.0CRCT-ND RES 22.0 OHM 1/8W 1% 0805 SMD  $0.08  $0.80 
R13310P1.50KCCT-ND RES 1.50K OHM 1/8W 1% 0805 SMD  $0.09  $0.91 
R14310P1.00MCCT-ND RES 1.00M OHM 1/8W 1% 0805 SMD  $0.09  $0.91 
R15,R16610P330KACT-ND RES 330K OHM 1/8W 5% 0805 SMD  $0.08  $0.77 
R31310311-32.4CRCT-ND RES 32.4 OHM 1/8W 1% 0805 SMD  $0.08  $0.80 
R31ALT310311-34.8KCRCT-ND RES 34.8K OHM 1/8W 1% 0805 SMD  $0.08  $0.80 
R32310311-11.5KCRCT-ND RES 11.5K OHM 1/8W 1% 0805 SMD  $0.08  $0.80 
RLED310311-604CRCT-ND RES 604 OHM 1/8W 1% 0805 SMD  $0.08  $0.80 

Misc
LED33160-1035-ND LED 3MM ALGAAS RED DIFFUSED  $0.20  $0.60 
USB33609-1039-ND CONN RCPT USB TYPE B R/A PCB  $0.97  $2.91 
PCB35AlienDAC PCB
X133X030-ND CRYSTAL 12.000MHZ 32PF HC-49/UA  $0.40  $1.20 



Parts Total $66.70 

Parts + Shipping to NZ $84.70 

NZ$ Equiv (rough) + Credit Charges $139.82
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post #129 of 1560
7/30/06 at 8:27pm
can someone tell me which leads at the usb's data + and data -? Is it the one connecting the R11 or R12. Thanks
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post #130 of 1560
7/30/06 at 8:27pm

Sick DAC Needs Exorcism

I finished my first board and I have some issues.... first, high res images are in my gallery. Click "Original" below the image to see full 6mp images.

Symptoms:

1. Absolutely no output on left channel
2. Right channel has low, distorted volume. See scope image of sine wave. The positive peak of the sine wave is bizarely inverted, which is why I think I may need an exorcism. I've never seen a sine wave like this in a tech book. This seems to be a newer problem that just developed.

History:

I had a tough time with the 2702 chip and my first attempt at wipe and flood resulted in flooding most of the pins. You can see from the images that the pins are very clean now. I am getting good voltage at the 3.3v and 5v rails, the 5v rail reading 4.72, which is where I set the adjustable reg. I have tried this with USB power and powered by 6xAAA with same results. I originally got a very strong good signal on the right channel, about 3Vpp at full volume. Now I am getting only 1V pp; the top of the sine wave is always distorted, regardless of the singal level- it is not simply clipping at + .5mv.

[Edit: I also shorted the pins of CL to eliminate a bad cap from the list of possibilities and this shorted pin arrangement is illustrated in the board bottom image. When powered by 6AAA the board draws about 38ma.]

As I understand the chip, there are only 3 pins that are channel specific- a Vcc, ground and output signal for each channel. I have measured signals at the closest pads to the pins while the DAC is running to verify that it is not a simple solder problem. Although I did not want to risk measuring voltage and signals directly at the pins, I did take resistance measurements between the top of the pins (where they enter the chip case) and adjacent pads to verify that the paths are clean, which they are.

Any help would be greatly appreciated. I have spent all day diagnosing this board and I am out of ideas.

Regards,
Neil
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post #131 of 1560
7/30/06 at 9:35pm
Thread Starter 
Hey guys,

I tried soldering the 2702 chip onto the board for several days, which out much success. What exactly is the paste and wipe method? If it is the method that Alf put on the Alien DAC page, I am getting a little confused.

I never used flux before, so I got the Kester paste flux, and used a cold iron to put the flux all over the board. I put the chip onto paste, and dip a very little solder onto the tip, and when I put the tip onto one of the pin, it does melt the flux on the board, but it doesn't seem to help the solder to get on the pin and the board. What did I do wrong here?

What exactly is the wipe procedure? Am I supposed to solder each pin very quickly after 2 corner pins are down? How do I do that?

Thanks for your help.

Thanks,
Peter
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post #132 of 1560
7/30/06 at 9:50pm
Quote:
What exactly is the paste and wipe method?
http://www6.head-fi.org/forums/showp...76&postcount=7

In short:
you simply apply flux, place the part, tack down the corners, clean the tip of your iron, load up the tip of the iron with solder and then "wipe" the tip across the pins.
Inspect the results with magnification to ensure there are no solder bridges.
If the solder doesn't stick to the pads you need to clean your tip better.


Quote:
I never used flux before, so I got the Kester paste flux,
what kind of paste flux?
I certainly hope you are not using acid flux cause that is not real good for the board and it would explain why it is not working.
If you do not know and cannot figure it out I would suggest that you buy a Kester flux pen ASAP.

link--------> http://www.hmcelectronics.com/cgi-bi...uct/4800-0039/
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post #133 of 1560
8/1/06 at 2:02am
Crap! I just got my digikey order before, and it apears i ordered the wrong ferrites. Would FERRITE ARRAY 400MA 75 OHMS SMD work? It apears as if it can be made to fit.

Rob.

[edit]: And can you really hear the difference between 5v and 5.4v? We are talking <.0002 THD+N and only a tiny increase in SNR.

Rob.
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post #134 of 1560
8/1/06 at 3:34am
Quote:
Originally Posted by robzy
Crap! I just got my digikey order before, and it apears i ordered the wrong ferrites. Would FERRITE ARRAY 400MA 75 OHMS SMD work? It apears as if it can be made to fit.

Rob.

[edit]: And can you really hear the difference between 5v and 5.4v? We are talking <.0002 THD+N and only a tiny increase in SNR.

Rob.
Well, the specified ferrite is 600R, those are 75R... and I think as long as it's 1206 package it'll fit.

I think from digikey, this is the best choice.
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post #135 of 1560
8/1/06 at 5:11am
Quote:
Originally Posted by Alf
Quote:
Originally Posted by Whitewind
The Ferrites I used are spec'ed at 75ohm. The Alien specifies 600ohm ferrites. Would there be any difference in the sound quality?
I recommend installing 600R ferrites. There would be measurable difference.
Damn. Sounds as if im shelling out on some new ferrites.. :P

Rob.
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