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Alien DAC v1.1 Construction Thread - Page 82

post #1216 of 1560
5/24/08 at 9:18pm
Quote:
Originally Posted by pinkfloyd4ever View Post
fyi: flux isn't conductive. People often recommend cleaning it just because it looks better cleaned and supposedly it can cause stray capacitance, but I've never had any problems with projects that I haven't cleaned the flux from
Besides that, you can literally immerse the whole board in alcohol before you install the electrolytics - no flux after that - even underneath.
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post #1217 of 1560
5/25/08 at 1:42am
Quote:
Originally Posted by tomb View Post
Jeff Rossel would be the first suggestion at Glass Jar Audio.

Rochester Electronics (Rochester Electronics - Leaders on the Trailing Edge of Technology) apparently has thousands of the REG101UA-A. Whether that means you have to buy thousands to get one, I don't know - but it's worth a call.

Otherwise, you may have to wait until September unless some nice Head-Fier has extras.
Using Octopart (?), Sierra IC seems to have some of each available:

reg101ua - Octopart
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post #1218 of 1560
5/26/08 at 11:50pm
I am planning on building an alien and I was wondering what output jacks people were using. (TRS or RCA) Also, what led do people recommend?
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post #1219 of 1560
5/27/08 at 2:53am
depends entirely on wha you want to feed and what leads you have. You wont notice much difference in sound. RCA's will porbably be more handy down the line.
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post #1220 of 1560
5/27/08 at 8:09am
Well, I ended up ordering the rest of all the parts from Jeff, should had done that 9 months ago when I ordered the boards, would had saved one intl shipping...

Well, until the parts arrive, I'll have time to make a PSU/mini-tread for it (i'll be using the regulated configuration @ 5.4v), I'll be integrating this on my SOHA, so should I take the power directly from the transformer (30vct 24va), or from the 12v points in the SOHA board.
Also how would I regulate this? would an LM317+LM337 on a protoboard do the trick or should I add capacitors or something to them?
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post #1221 of 1560
5/27/08 at 9:38am
Quote:
Originally Posted by DolbyR View Post
Well, I ended up ordering the rest of all the parts from Jeff, should had done that 9 months ago when I ordered the boards, would had saved one intl shipping...

Well, until the parts arrive, I'll have time to make a PSU/mini-tread for it (i'll be using the regulated configuration @ 5.4v), I'll be integrating this on my SOHA, so should I take the power directly from the transformer (30vct 24va), or from the 12v points in the SOHA board.
Also how would I regulate this? would an LM317+LM337 on a protoboard do the trick or should I add capacitors or something to them?
You're wanting to power your AlienDAC from the SOHA? I would just use an LM317 or LM7805 on protoboard, from the 12V supply on the SOHA, then you can skip reimplementing a rectifier and get better noise performance too. Put at least a couple uF at the input and output and you should be fine.
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post #1222 of 1560
5/27/08 at 11:34am


I could use this schematic probably? I would need 2 of these (1 for + and 1 for -) correct?

According to the calculator on the same website, with R2 regulated to 910 ohms, I should get an output of around 6 volts. Or nearly 6.5v at 1Kohm.
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post #1223 of 1560
5/27/08 at 12:23pm
Quote:
Originally Posted by DolbyR View Post


I could use this schematic probably? I would need 2 of these (1 for + and 1 for -) correct?

According to the calculator on the same website, with R2 regulated to 910 ohms, I should get an output of around 6 volts. Or nearly 6.5v at 1Kohm.
Can you clarify what you're going to be powering with this hypothetical supply? AlienDAC needs 5V and 3.3V, there is no negative supply. If you're going to the trouble of building an outboard regulator, I don't really see the point of the 5V REG101 at all.

Set up a LM317 (or LM7805) from the +12V rail of your SOHA, and set it to output 5.0V. Run that to the AlienDAC's input and configure it for 'unregulated' operation. You'll only need the 3.3V regulator, and if you can't get one, you can always build another LM317-based one and do it outboard.
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post #1224 of 1560
5/27/08 at 12:38pm
What I want, is to lower the power from the soha, from 12v to under 10v as the REG101s can not handle more than that..or to build a dedicated external supply for the DAC.
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post #1225 of 1560
5/27/08 at 1:30pm
Quote:
Originally Posted by DolbyR View Post
What I want, is to lower the power from the soha, from 12v to under 10v as the REG101s can not handle more than that..or to build a dedicated external supply for the DAC.
In that case, I would do as I suggested in the last post:

SOHA +12V -> LM317/LM7805 5V -> AlienDAC

Omit the 5V REG101, include the 3.3V unit. You could include the 5V regulator if you want to, and bump up the pre-regulator output to 6-7V, but I don't personally see the benefit.
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post #1226 of 1560
5/27/08 at 1:36pm
Quote:
Originally Posted by error401 View Post
In that case, I would do as I suggested in the last post:

SOHA +12V -> LM317/LM7805 5V -> AlienDAC

Omit the 5V REG101, include the 3.3V unit. You could include the 5V regulator if you want to, and bump up the pre-regulator output to 6-7V, but I don't personally see the benefit.
Thanks,
as the parts are already on their way, and with the REG101UA-A, adjustable regulator and the corresponding resistors to get 5.4v "overclocked" configuration, I prefer using the onboard reg (i'll feel safer as I wont need to adjust the LM317 that accurately).
What about the schematic I posted before? Is it fine for my applications. I'll be using the 317, as I already have 20 or 30 of them at home.
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post #1227 of 1560
5/27/08 at 3:18pm
Quote:
Originally Posted by DolbyR View Post
Thanks,
as the parts are already on their way, and with the REG101UA-A, adjustable regulator and the corresponding resistors to get 5.4v "overclocked" configuration, I prefer using the onboard reg (i'll feel safer as I wont need to adjust the LM317 that accurately).
What about the schematic I posted before? Is it fine for my applications. I'll be using the 317, as I already have 20 or 30 of them at home.
Sure, it'll work great. You might add an electrolytic (a couple hundred uF is more than enough) on the input, depending on the cable length from the SOHA's power supply. Since you're using the REG101s anyway it doesn't really matter, but you may want to use the 'Improved Ripple Rejection' schematic instead. It's on page 15 of the National datasheet. Basically it just adds a 10uF capacitor across R2, and will lower the output ripple. Since you're taking a regulated input and regulating it twice again (LM317 then REG101), you really don't need the extra ripple rejection. At ~65dB per stage, ripple should be down a whopping 195dB by the time it gets to the PCM2702 - which on its own has quite good ripple rejection.

The only thing I might be concerned about is load on the little LM78L12 in the SOHA. It can only supply 100mA. The SOHA opamp shouldn't draw more than ~15mA. PCM2702 has a max of 30mA at 3.3V plus 25mA at 5V. Some quick maths and you end up with the LM317 pulling ~170mA, most of which gets burnt off as heat. You might get away with it, but really it's too much for the 78L12. You should substitute a full-size LM7812, or use your original plan and build a separate rectifier/regulator to power the DAC. Or just use USB power...
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post #1228 of 1560
5/27/08 at 3:28pm
Great, thanks a lot.
I guess while I'm at it, I'll upgrade the regs (maybe even to 15v regs as suggested for Jisbos - as this will probably be the next upgrade).
The only thing that Iäm stilll confuses about is the wiring.
On the AlienDAC webpage it says that for amp powered. Connect the amp’s V+ to the AV+ pad, amp’s V- to the AV- pad, and amp’s ground to the AG pad.
Is this only for amps with virtual ground, AFAIK, SOHA is not a virtual ground amp and the BUF634 would not be necessary...so would the output from 317 go to AV+ and the v- from SOHA to the G2 pad?
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post #1229 of 1560
5/27/08 at 4:32pm
Quote:
Originally Posted by DolbyR View Post
Great, thanks a lot.
I guess while I'm at it, I'll upgrade the regs (maybe even to 15v regs as suggested for Jisbos - as this will probably be the next upgrade).
The only thing that Iäm stilll confuses about is the wiring.
On the AlienDAC webpage it says that for amp powered. Connect the amp’s V+ to the AV+ pad, amp’s V- to the AV- pad, and amp’s ground to the AG pad.
Is this only for amps with virtual ground, AFAIK, SOHA is not a virtual ground amp and the BUF634 would not be necessary...so would the output from 317 go to AV+ and the v- from SOHA to the G2 pad?
SOHA is not a virtual ground amp - it uses a bipolar supply and doesn't have a driven ground channel.

The only purpose of the -ve supply in the AlienDAC is to drive the BUF634, which is only required for virtual ground amps - so you don't need it. Rig your 6V regulator and connect it to AV+. Connect the amp ground to G2. You're basically doing the 'external PS' configuration. Since your amp has a bipolar supply, you don't need to worry about the AV- and BUF634.
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post #1230 of 1560
5/30/08 at 2:40am
Well, the difficult parts are all soldered on, except for RLED. Just easy stuff left. All the pins on the PCM2702 really are connected in spite of that dark spot...Tool #2 for this work was a 10x jeweler's loupe!

I am enjoying this micro-soldering very much!



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