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Alien DAC v1.1 Construction Thread - Page 28

post #406 of 1560
10/2/06 at 5:15pm
Quote:
Originally Posted by t52
here are some pictures of the second one i built, this time with a nice wood case
http://t5.xlhost.de/Photos/DIY%20Projects/Alien%20DAC
Wow! Such a large case for such a small thingy! It looks great, though. Good job!
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post #407 of 1560
10/2/06 at 5:22pm
Quote:
Originally Posted by Alf
Wow! Such a large case for such a small thingy! It looks great, though. Good job!
thanks a lot!
i have several of these cases now and they stack up to a nice "mini component system"
pics here: http://t5.xlhost.de/Photos/DIY%20Projects/Wood%20Cases
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post #408 of 1560
10/2/06 at 6:04pm
Quote:
Originally Posted by ssmrsx
Hi all,

I am just wondering has anyone compare the audio quality btw the Alien DAC and the TI development board? http://focus.ti.com/docs/toolsw/fold...m-pcm2702.html
Which design you would suggest excluding the cost factor?


Thx in advance!!

Anyone???
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post #409 of 1560
10/2/06 at 6:07pm
Quote:
Originally Posted by ssmrsx
Anyone???
the ti development board doesn't even use proper voltage regulators, ferittes on the supply inputs of the chip etc., so i'd recommend the alien dac.
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post #410 of 1560
10/2/06 at 8:02pm
Quote:
Originally Posted by t52
thanks a lot!
i have several of these cases now and they stack up to a nice "mini component system"
pics here: http://t5.xlhost.de/Photos/DIY%20Projects/Wood%20Cases

The case is really nice. Since you have some space available I would propose two modifications to your current config:

1: Regulate the power supply. You can build a LM317 based PS very easily on a bread board and it will provide the DAC with much better filtered power.

2: Try some more "exotic/boutique" capacitors and let us know the sound differences.
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post #411 of 1560
10/2/06 at 8:05pm
Quote:
Originally Posted by MASantos
The case is really nice. Since you have some space available I would propose two modifications to your current config:

1: Regulate the power supply. You can build a LM317 based PS very easily on a bread board and it will provide the DAC with much better filtered power.

2: Try some more "exotic/boutique" capacitors and let us know the sound differences.
1. the psu is regulated, i used a lm7809, after the regulator i have a 22ohms series resistor and a 2200uF low esr cap for additional filtering.
hopefully i will have time to compare it to the "cheap" unregulated version soon.

2. there's just so many projects on my wishlist, including some "real" speakers (with thiel coax chassis), so boutique caps are surely someting for the future... btw. hat's you're favourite "exotic" cap?
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post #412 of 1560
10/4/06 at 2:52am
Hi guys,

After reading this tread, I've just finished putting together 2 BOMs, one for a USB powered regulated version and another for an externaly powered version.

Could you guys take a look to make sure it's fine and that I've selected good parts. They're identical except for R32 resistor choices.

Also, correct me if I'm wrong, but with the AlienDAC, there's still enough room to stick a small mini TREAD inside the Hammond 1455C802 with it. Of course I'll go with a small cap, no huge 1000uF/63V.

Thanks!
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post #413 of 1560
10/4/06 at 5:43am
Quote:
Originally Posted by FallenAngel
Hi guys,

After reading this tread, I've just finished putting together 2 BOMs, one for a USB powered regulated version and another for an externaly powered version.

Could you guys take a look to make sure it's fine and that I've selected good parts. They're identical except for R32 resistor choices.

Also, correct me if I'm wrong, but with the AlienDAC, there's still enough room to stick a small mini TREAD inside the Hammond 1455C802 with it. Of course I'll go with a small cap, no huge 1000uF/63V.

Thanks!
I think that fitting a tread inside that case with the alien is almost impossible.
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post #414 of 1560
10/4/06 at 1:06pm
I did say mini-tread, but if a full-blown tread would be "almost impossible", I think I'll be able to fit a dumb-downed version of one.

Thanks.

How does the BOM look? Nothing off?
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post #415 of 1560
10/4/06 at 1:40pm
Quote:
Originally Posted by FallenAngel
I did say mini-tread, but if a full-blown tread would be "almost impossible", I think I'll be able to fit a dumb-downed version of one.
I've been thinking about making a mini-tread too (both for my Alien DAC in a C801, and my PPAS in a J1201). For the Alien DAC the fit will definitely be harder, I've got a 6V AC wall-wart I was going to use. For the PPAS I've got a 24V wall-wart that outputs DC, so I'm leaving off the entire diode bridge and filter cap section before the regulator as per a comment in tangent's writeup.

I notice in your breadboard tread you didn't use a heatsink for the lm317... is that because you're not regulating it down that much from the input voltage? I only need about 150mA maximum of current to run and charge the PPAS, and was going to output something like 22V from the lm3117. I haven't measured the current draw of the Alien DAC, but was going to set the output to about 6V. If I could get away with a to-92 version of the lm317, that would end up saving a lot of space. Does anyone think that would be possible? I was also thinking of mounting the to-220 underneath so it was heatsinked by the enclosure.
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post #416 of 1560
10/4/06 at 1:52pm
The TO92 version, LM317L is only guaranteed for 100mA so I wouldn't try for 150mA with it.

As for the heatsink, I've never really used it for any of my builds because I never really saw the need. The LM317 always stays cool for me. Even with my PINT (output set at 13.75V, current draw of around 55mA if charging and listening at same time) off a 24V wallwart, it doesn't heat up at all and I measured using the most sophisticated equipment known to man, the all-mighty finger touch test.
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post #417 of 1560
10/4/06 at 2:09pm
Quote:
Originally Posted by FallenAngel
The TO92 version, LM317L is only guaranteed for 100mA so I wouldn't try for 150mA with it.
D'oh. Reading > me. I could have sworn it said 200.

Quote:
Originally Posted by FallenAngel
As for the heatsink, I've never really used it for any of my builds because I never really saw the need. The LM317 always stays cool for me. Even with my PINT (output set at 13.75V, current draw of around 55mA if charging and listening at same time) off a 24V wallwart, it doesn't heat up at all and I measured using the most sophisticated equipment known to man, the all-mighty finger touch test.
Hmm. Then I can probably just leave it up on top.
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post #418 of 1560
10/4/06 at 10:51pm
Happy Birthday Alf
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post #419 of 1560
10/8/06 at 6:29pm

problem with different output levels on l/r

i have a weird problem with the second board i built here. after first listening to it the left channel was dead. so i got back to the board and found that the pcm2702 leg with the left out was not connected to the pcb (no short though!). after resoldering it, it works but the output level is abt. 20% lower than the right channel. checked the connection with a dmm and it's ok now. anybody haave a clue?!
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post #420 of 1560
10/9/06 at 6:14am
some more info on my problem: the dc offset on both channels is the same within 1mV, i also checked with a dmm in the 200kohms range from output to ground (before output caps) and measured 2x ~90kohms, also identical (dac off).

i also looked at the output with my old scope (built 1969, all tubes) which is not very precise, but both outputs show a nice sine wave form when fed with a 1khz mono sine signal... it's just that one channel's amplitude is lower.

could it have something to do with the digital attenuator in the chip (probably being programmed to some value on one channel)? i don't even know if the attenuator can be set explicitely for one channel only. nor do i know how to set it at all, can someone shed some light on this or should i contact ti about this?

if it's not a "software" problem, i probably have a broken chip here...
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