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Old 12th June 2012, 08:23 PM   #2521
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I had one of the faulty ones, a friend check why it wasn't working and it turned out that two of the cables at the comp end had been clamped in wrong positions... Changing the cable also took care of the high frequency noise from the inductor on the top right end. Hope that helps.
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Old 12th June 2012, 08:52 PM   #2522
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Quote:
Originally Posted by Nikola Krivorov View Post
I had one of the faulty ones....it turned out that two of the cables at the comp end had been clamped in wrong positions...
Can you clarify as to what you mean? What cables are you talking about? USB, twisted pair? The 'comp end'? And how come two of them? Seems a bizarre coincidence. Were they self-constructed USB cables?
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Old 12th June 2012, 09:04 PM   #2523
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Quote:
Originally Posted by swalter View Post
No need to beg ok, but seriously, have you tried a different USB cable, I had two faulty ones already... another thing to test would be if the hiss disappears with the 3.5mm connector, if both fails I send you a new one, but need the little hisser in return

Stefan
One of the two faulty USB cables that Stefan had sent to customers with the odac. They look perfectly fine on the outside but the computer doesn't recognize the DAC. My friend disassembled it and the defect was definitely due to bad manufacturing.
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Old 12th June 2012, 09:07 PM   #2524
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Quote:
Originally Posted by Nikola Krivorov View Post
One of the two faulty USB cables that Stefan had sent to customers with the odac. They look perfectly fine on the outside but the computer doesn't recognize the DAC. My friend disassembled it and the defect was definitely due to bad manufacturing.
Great, thanks for that.
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Old 12th June 2012, 09:16 PM   #2525
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My next idea is to shock protect the O2/ODAC.

It occurs to me that they are vulnerable to being dropped. The ODAC also presumably has lead-free solder and so is more vulnerable.

I'm going to file down the sides of the PCB and add a thin layer of rubber glue to each side and then slide it in with the help of a little silicone grease. I might instead attach thin foam sheet if I can find some. However some of the plastics/synthetics out there give off fumes that rot other plastic parts. I reckon the rubber glue is safer. Perhaps cardboard is another option.

I think I'll widen the front plate holes also as they are right up against the switches/jacks.

Might have to file the case to give the ODAC some leeway as well: it's pretty tight.

Anyone else got practical improvement ideas?

Last edited by lorriman; 12th June 2012 at 09:27 PM.
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Old 12th June 2012, 09:27 PM   #2526
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Well, I'm listening to my O2/ODAC combo with my ety HF2s knowing I have authentic HIFI all the way down the chain.

I'm so pleased I could bite myself.

A big thankyou to NwAvGuy. It's not just that I have reached source/amp Nirvana but also that I had the great satisfaction of building it myself, even though a newbie to this lark, because his instructions were so thorough. Even my various skeptical relatives have been astounded.

I though the O2 was a fantastic project. Though I didn't have the satisfaction of building the ODAC nevertheless for what it means and gives it really is another dimension of marvellousness.

I'll be raising a glass of Bourbon to his honour later this evening.

Last edited by lorriman; 12th June 2012 at 09:55 PM.
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Old 13th June 2012, 01:20 AM   #2527
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When I wrote 'knowing' I should have written 'reasonably confident'. Some one chastise me for my dreadful unobjective sin.
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Old 13th June 2012, 05:23 AM   #2528
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Quote:
Originally Posted by swalter View Post
No need to beg ok, but seriously, have you tried a different USB cable, I had two faulty ones already... another thing to test would be if the hiss disappears with the 3.5mm connector, if both fails I send you a new one, but need the little hisser in return

Stefan
Thanks Stefan. I have tested with 3 different USB cables of which I tested yours for the first time last evening. Still hissing.
I will solder the 3.5mm to the card tonight.

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Old 13th June 2012, 07:21 PM   #2529
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I have a Sennheiser HD 650 (300 ohm impedance) and a AKG K550 (32 ohm). What should O2's high gain and low gain settings be to match these 2 headphones? Thanks.
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Old 13th June 2012, 08:37 PM   #2530
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Originally Posted by litster View Post
I have a Sennheiser HD 650 (300 ohm impedance) and a AKG K550 (32 ohm). What should O2's high gain and low gain settings be to match these 2 headphones? Thanks.
There are two approaches to anser your question: max power limitations of the headphones or max listening volume you'll ever experience (or to raise volume for overly quiet recordings).

If you want max power limitations, here they are:
HD650
0.5V source (portable device) = 6.85x gain
2.1V source (redbook + 5% room) = 2.6x gain
SPL at those levels = ~118dB (ouch)

K550
0.5V source (portable device) = 3.15x gain
2.1V source (redbook + 5% room) = 1.2x gain
SPL at those levels = ~122dB (crazy nuts)


If you want reasonable figures, which I cap at 110dB from a -0dBFS source:
HD650
0.5V source (portable device) = 2.8x gain
2.1V source (redbook + 5% room) = 1.1x gain

K550
0.5V source (portable device) = 0.8x gain
2.1V source (redbook + 5% room) = 0.3x gain

So in conclusion, I'd have high gain set to 4x and low gain unpopulated, making it 1x (unity). The reason I'd have 4x is to provide enough headroom to amplify really quiet signals. I have some recordings that are around -20dB. If you don't have that situation, then set it back a little because a full knob turn can become dangerous.

Last edited by ethanolson; 13th June 2012 at 08:42 PM. Reason: revised language and formatting
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