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PCM2702 USB DAC Revision B - Page 45

post #661 of 670
5/16/07 at 10:05pm
Quote:
Originally Posted by GregVDS View Post
Thanks, I should definitely try to build this one. I plan to use is as source for a SOHA I already finished (with crossfeed, custom built output buffers and Epsilon12 protection). Can I simply join the outputs of the Alien DAC to the RCA inputs of the amp, without fussing with input switch, or the Alien DAC will have a bad influence when not used on the RCA signal? I mean the CL/CR could play for both system, right? I don't remember if the SOHA has DC input protection, I should check that. What is the best choice for CR/CL (discussed at libitum, I know, but a resumé of all the thread would be nice) if I have to put them in? As I understand, the Alien DAC is producing DC offset that has to be blocked, internally, or by the amp, right?

I never soldered SMD, but am reading all tutorials available. Is it ok to go unregulated USB power? What should I expect in comparison with the stock headphone output of my Macbook (sound quality point of view, apart from the SOHA influence)?

All the very best,

GregVDS
Regarding the CL/CR, I have done some extensive testing with different caps( FM's, Elna's, Nichicon's, Black Gates) and the best IMO is the 4.7uf BlackGate High-Q Nx. It takes some time to break in but gives the best sound. But if you have space in your enclosure and are willing to spend the money, you could go with some nice "boutique" film caps.

Manuel
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post #662 of 670
5/16/07 at 10:54pm
Quote:
Originally Posted by GregVDS View Post
...
Is it ok to go unregulated USB power? What should I expect in comparison with the stock headphone output of my Macbook (sound quality point of view, apart from the SOHA influence)?
I recommend using the REG101UA to regulate the USB power rather than unregulated. The computer's 5V line can be quite noisy. My own testing shows no tangible improvement with external power (over regulated USB power), even when that external power is a battery.

The Alien DAC should be a nice upgrade over the onboard sound of virtually any computer, especially laptops. It could do only 16-bit and either 44.1KHz or 48KHz sampling rates, though; but that shouldn't be a big issue with computer audio.

Btw, there is a dedicated Alien DAC thread with lots more info.
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post #663 of 670
5/17/07 at 12:18pm
What gives with that battery?

Without plugging the USB, this circuit won't work. Plug in the USB and the battery start to drain.
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post #664 of 670
5/17/07 at 3:39pm
Quote:
Originally Posted by jasonhanjk View Post
What gives with that battery?

Without plugging the USB, this circuit won't work. Plug in the USB and the battery start to drain.
The USB is plugged in, of course, but the Alien DAC I built has a switch that lets me select +5V power from the USB bus or from an external source.
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post #665 of 670
6/27/07 at 12:36pm

Do I need a DAC or not?

Hey Guys,


New to this scene, wanted to know if I needed this DAC when using my Shure E530 with a Xin Reference Amp for use on my computer. I don't want to change the sound, hopefully want to improve it, can someone help?

I know using an amp in the signal path does improve the sound, but I think I still wanted a good inexpensive DAC (USB) to use with my computer (X-Fi Extreme Music soundcard)

Thanks in advance for your guys help
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post #666 of 670
6/28/07 at 1:27am
^ I'd guess you would notice quite an improvement using this DAC, after all the source is the most important part of the signal chain. Soundlaster cards are generally crappy for music (cheap onboard DACs).
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post #667 of 670
6/29/07 at 12:06am
who is selling the latest revision PCBs?
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post #668 of 670
6/29/07 at 12:08am
http://glassjaraudio.com/
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post #669 of 670
7/11/07 at 7:25pm
I'm afraid I killed my beloved bus-powered DAC. I built it a week ago and have been enjoying it while i wait for an enclosure. I brushed my hand against the back of the board, and one channel was gone. I fished around with my output wires to make sure they hadn't touched, and *poof* both channels are dead.

I've rebooted, replugged in and I've checked both voltage test points. That's about the extent of my troubleshooting experience. Where else should I probe around or what else should I try? I'm really hoping I didnt kill the pcm2702 with static discharge. Help?
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post #670 of 670
9/16/07 at 8:07am

One channel down :(

I've also managed to kill one of my channels, I'm not sure how. The other works fine, my voltage test points are good and I've swapped the output caps round to make sure they're not the problem. From the look of the schematic I'm thinking there's not much else apart from the chip that I could have killed, anyone got any suggestions please?

Thanks
Simon
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