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Alien DAC v1.1 Construction Thread - Page 42

post #616 of 1560
2/20/07 at 4:46pm
could also be a short to ground of the 3.3v rail, check your pcm2702 for solder bridges...
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post #617 of 1560
2/24/07 at 5:30pm
Hi people.

I would like to improve the sound from my computer, and this looks real promising. I have a DIY class-D amplifier (using Hypex modules), and would like balanced outputs. I realize that this could probably be added using a couple of opamps on each output.

My second choice is running with what you have here, and connect the negative signal to ground at the sound-card end. That should give me some advantage over non-balanced outputs if i understand correctly.

The question really is, if adding balanced outputs, what would need to be done? Would it seriously impair the sound quality (using decent op-amps of course)? Would I get the same noise dampening features by just soldering - to gnd in the connector?

My problem is that there are quite a lot of noisy stuff close to my signal cable, and using a balanced cable has really improved the noise situation.

A last couple of question:
Does the circuit make noise when connected/disconnected from USB/power? I am hoping to be able to keep my amp powered at all times, and I am not using a preamp eighter.
I would believe that lowering the volume from the card would be done digitally, effectively reducing the resolution of the signal when not running at 100% (50% would be 15bit, 12.5% = 13bit and so on). Is that the case, or is it really reduced analogly? If not, I want to also add a manual level attenuator so that I can run it at 100% all the time.

Thanks
-Ko_deZ-
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post #618 of 1560
2/25/07 at 5:45am
Quote:
Originally Posted by FallenAngel View Post
Yep, does look like a pretty nice kit, could improve upon a few things (I mentioned this earlier in another thread), mainly change the voltage regs to TO220 package vs TO92, and definitely change the Opamp to an OPA2107 (very very nice) and you're good. The only other thing is, the kit doesn't include the expensive stuff like the transformer, POT, enclosure or any of the casing things.
Hello, I really need to read all these threads more often. I will incorporate those changes into the kit. Is the 2107 a direct drop in, or are there any changes that need to be incorporated? I originally bought parts from a much earlier BOM, so I have some parts that are from an earlier design. For instance, I have a bunch of Triad split bobbin transformers gathering dust. (-: Note to self: package up those paper weights to return to Mouser...

But I do offer a complete kit, and my kit is flexible and dynamic as I get more options added. You can check up on the kits here: http://www.geocities.com/jeffrossel/ . Also I have a standard kit listed at my website: www.glassjaraudio.com

Contact me from one of those sites for further information. w

I have been busy shopping for JAN NOS 5963 tubes along with some triple mica 6189 black plate tubes to offer, and will be testing them and listing them as options. I also found some side getters RCAs, so I will be able to feed people's addiction to rolling tubes. I'm starting to feel like a pusher here...

Talk to you later
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post #619 of 1560
2/25/07 at 6:24am
Quote:
Originally Posted by Yen View Post
Do you sell PCBs only?
I will provide boards alone or included within the kit. The boards will probably be less costly than the last group buy (barring any large changes in the Euro to Dollar exchange rates). Hopefully the PC board fabricator will make them with the same process as the last time. They should ship in mid March. I ordered a lot of them, so we should be covered for a few months...

JR
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post #620 of 1560
2/25/07 at 10:05pm
Will you be offering a parts only kit also ?

I bought pcbs a while back, but sourcing components is a pain here in Australia (I don't like the idea of paying $50 postage for a $12 part !).
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post #621 of 1560
2/25/07 at 11:28pm
$50 postage ?

For about $250 worth of parts I paid $30 shipping.

Although yes, if you're getting only a handful of stuff shipping can be pretty expensive.That's when you make a post here and hope someone helps you out, as you have done.
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post #622 of 1560
2/26/07 at 12:06am
Where did you order from ?

I'm keeping an eye out for some PCM2702's, but both digikey and mouser are fairly expensive when it comes to shipping. They use either fedex or UPS, which aren't really useful when ordering tiny smd devices from overseas
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post #623 of 1560
2/26/07 at 2:26am
From digikey, although yes I wouldn't order off them for only a few parts. Like I had most of the components for the PINT except a few I couldn't source here, so I tacked on those few onto my Alien DAC order.

Like right now I need some low esr caps and so I'll add them on to the next order I make when a project comes up.
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post #624 of 1560
2/26/07 at 6:18pm
Hey, just a quick question guys, what exactly is the purpose of the 2 330K resistors between the output of the output caps and ground and why was this value chosen?

Mainly wandering because I changed the values from suggested quite a bit and was curious if these resistors should also change.

Thanks
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post #625 of 1560
2/26/07 at 10:12pm
Darn,

getting like .8 v @ the 3.3 and .9v at the 5 v test point and IC - 1 is gets really hot.

Is IC 1 fried already?

I have these two multimeters:

dm-50

and

sperry 10-a

I understand that the pins are closed when the resistance is 0, and open when it is at infinity. However, which ohm level should I test the pins at?

Thanks,
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post #626 of 1560
2/26/07 at 11:02pm
Garlic, pics buddy, it'll help. Basically, is your regulator backwards?
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post #627 of 1560
2/26/07 at 11:25pm
Goodness, I suck. You rock.

IC 1 is backwards.

Is the chip dead or if I desolder/resolder do I have a chance?

Crap almighty, I honestly went pin by pin on IC 1 laboriously but now, it seems, to no avail.

Jeez,

Thanks though.
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post #628 of 1560
2/26/07 at 11:47pm
No worries, I did the same thing to one of mine as well, you can desolder that thing and put it back on without problems. Just don't overheat for too long.
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post #629 of 1560
2/27/07 at 3:19am
Quote:
Originally Posted by FallenAngel View Post
Hey, just a quick question guys, what exactly is the purpose of the 2 330K resistors between the output of the output caps and ground and why was this value chosen?
http://www.head-fi.org/forums/showpo...&postcount=169

I don't know how a different value would affect it though. I suspect using lower values would be worse.
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post #630 of 1560
3/2/07 at 7:13am

More RMAA tests on the Alien DAC

Quote:
Originally Posted by Calroth View Post
I have performed RightMark Audio Analyzer testing on my Alien DAC...
I re-did the tests; here are the results. The test methodology is the same as last time: took a PC and sent its on-board Realtek ALC850, Alien DAC and Chaintech AV-710 high-quality output to a MacBook Pro.

Changes are:
  • input device is now an M-Audio FireWire Audiophile; much more accurate
  • got rid of the Sound Blaster USB
  • added a baseline: the FireWire Audiophile is the "loopback" device
  • you can now download the results file for your personal gratification! Click the "download" link
As before, any questions, post and I'll follow up. Also, other people's experiences are welcome, as there are quite a few "So, how good is the Alien DAC anyway?"-type posts.
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