'noodle' dac (ebay special)
Sep 11, 2008 at 6:51 PM Post #76 of 180

gurusan

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I bypassed the entire output stage on the DAC so the analogue signal is going straight to my cmoy and it sounds very, very good!

I used to have a X-FI with a bunch of mods which sounded pretty decent but this certainly beats it!
 
Sep 12, 2008 at 3:49 PM Post #77 of 180

gurusan

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Got everything stuffed into the case with some ventilation. Casework is much harder than I thought! Couldn't get things to line up properly and I got fed up after awhile... now its good enough for me, even though the rear of the case is a bit rough, lol. I might have another go with a new case in the future.


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Oct 2, 2008 at 11:30 AM Post #80 of 180

fordgtlover

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Everyone with this DAC should check out this post over at theartofsound.

I did the mod that the poster mentions, but also did a whole bunch of other changes so I can't confirm the results.

My version of this little DAC is sounding very nice; very revealing.
 
Oct 25, 2008 at 8:42 PM Post #81 of 180

gurusan

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So....without any warning my DAC started buzzing a whole ton through the outputs...the little crappy transformer that came with the DAC got VERY hot and started to melt my case.

Any idea what could have caused this? it was working fine for over a month. Just a cheapo transformer? What kind would you recommend for a cheap but good replacement?

I wonder if the DAC itself is still good...
 
Oct 26, 2008 at 10:01 AM Post #83 of 180

gurusan

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So I'm looking for a suitable replacement transformer for the DAC. Can anyone recommend one that is not very expensive, but won't fail like the last one did?

I need one that will output 12V on the secondaries, correct? What sort of VA rating should I look for? I understand the DAC does not take much current but will there be any better regulation with a higher VA rating?
 
Oct 26, 2008 at 11:19 AM Post #84 of 180

mwofsi

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Quote:

better regulation with a higher VA rating


I think that for transformers regulation refers to the difference between loaded and unloaded voltages. For an ic regulated supply this shouldn't be a problem as long as the rectified unloaded voltage (x1.42?) doesn't exceed the component ratings for things such as caps in the power supply (I believe Tangent suggests [rectified unloaded voltage x 2] as a safer way to determine cap voltage ratings). I'll offer more comments and suggestions if those more knowledgeable don't chime in.
 
Oct 26, 2008 at 6:16 PM Post #87 of 180

mwofsi

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Quote:



Power to spare I should think. Isn't it a little large?

Looking at the ebay photos on gigaworks, they show dual 9V secondaries, with a 0.39A (390mA) capability for each. I make that 14VA which should also be more than adequate.

If your not going to use the dacs opamp output stage you wont need the +/-12V part of the supply and may be able to get away with a smaller voltage, even if the power supply is wired so that everything goes through the 12V regs. Say add 3V for the 7805 dropout voltage that's 8v rectified, one 6V secondary of perhaps 100-150mA would do. That would greatly reduce the heat output. EDIT; not 100% sure on that 'cause I 'm not sure how a regulator would behave with such a low voltage going through it.
EDIT: I'm also making the huge assumption that the opamp is supposed to use a bipolar supply (+/-12V), as I only have a partial circuit diagram.
 
Oct 26, 2008 at 6:51 PM Post #88 of 180

gurusan

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Well the output stage is already completely bypassed. My RCA outputs are tapped directly into the +R and +L from the receiver.

This is the transformer that came with it (the one that got super hot and melted my case)


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Oct 26, 2008 at 7:07 PM Post #89 of 180

mwofsi

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In that case you obviously have no need for a +/-12V supply, just the regulated 5V, which gets fed to the dac board and is there also regulated to 3.3V.

Bit concerned about the melting transformer. A small enough fuse might have stopped it. Possible cause: a faulty transformer, a wiring short, or the heat in your case being to much for it and causing a fault.

I believe the VA rating of your transformer is (12+12)x(0.292+0.292)=14VA. Should have been adequate if all was well.

btw seeing as I just burned a TLE in the same way, both this and your cmoy supply secondaries are isolated from mains earth aren't they?

Another thought, is your cmoy power supply capable of providing a power feed to your dac? Separate supplies are often preferred but it may work well
 

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