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Brief Odac impressions
Jun 8, 2013 at 3:23 AM Post #1,666 of 2,018
I have the RCA outputs hooked up to my amp which connects to my headphones. At the same time I have the 3.5mm out connected to a pair of active speakers. If I play some music, I can hear it on both the headphones and speakers simultaneously. So it appears to work.
 
Jun 9, 2013 at 4:21 PM Post #1,669 of 2,018
Quote:
beaver316 said:
I have the RCA outputs hooked up to my amp which connects to my headphones. At the same time I have the 3.5mm out connected to a pair of active speakers. If I play some music, I can hear it on both the headphones and speakers simultaneously. So it appears to work.
Click to expand...

 
Why does a headphone amp have two RCA inputs? For balanced headphones with left and right channels carried via two separate cables?
 
Jun 10, 2013 at 10:22 AM Post #1,670 of 2,018
From JDSLabs site for the ODAC with RCA outputs:
 
RCA Output - RCA output jacks at rear, 3.5mm output and USB jack at front. Black endplates. 95mm case length. Note: The ODAC supports only 1 output; do not use 3.5mm and RCA jacks simultaneously.
 
I have tested this on a few downstream amps and have experienced distortion etc....depending on the amp being driven and its 'electrical' characteristics....
 
In one case I had the RCA analog output connected to a Onkyo receiver to drive a set of large speakers..so i could use the dac and pc flac source etc....this works well.
 
Then I connected the mini-jack analog to the O2 while the RCA analog was still cabled to the receiver even though it was powered off.
 
The sound in the headphones was distinctly less than "stellar' like it normally is.
 
When I realized this i removed the RCA cables and instantly back to great sound, no distortion etc..
 
When you add mulitple complex loads to things designed to handle single loads interesting things can happen.
 
This is one reason I have several 02 amps and ODACS.
 
Alex
 
Jun 15, 2013 at 4:03 PM Post #1,672 of 2,018
Love my ODAC-O2 from Epiphany Acoustics, but the input jack of my AC-adaptor bends very easily. It consists of two parts, the connector itself, and the adaptor with the cable, which is connected to the connector by way of two very soft metal prongs. They have already been bent two times by almost no handling at all. Since my ODAC-O2 is not strictly stationary, I transport it from time to time, however the plug bends by almost nothing at all. I think it will break sooner or later. It would be more robust if the cable and adaptor would just be one part. What would a replacement cost in case of a broken plug or by way of precaution? (How would you rate the robustness of the ODAC-O2 itself? Can things break in it by it slipping to the ground (about 70 cm)? So far, it has happened only once, because the cable got caught, although I was still very near to it.)
 
Jun 18, 2013 at 8:50 AM Post #1,675 of 2,018
The WAU20-200 doesn't result in any higher output into high impedance headphones (because the O2 uses a regulated power supply internally) and it has less current for low impedance loads.
 
The WAU16-400 is the best transformer for any headphone.

The 18 and 20 volt transformers do put more of a thermal "strain" on the O2 as the regulators run hotter.
 
A.
 
Jun 20, 2013 at 12:16 PM Post #1,676 of 2,018
Quote:
adydula said:
The WAU20-200 doesn't result in any higher output into high impedance headphones (because the O2 uses a regulated power supply internally) and it has less current for low impedance loads.
 
The WAU16-400 is the best transformer for any headphone.

The 18 and 20 volt transformers do put more of a thermal "strain" on the O2 as the regulators run hotter.
 
A.
Click to expand...

So, is it better than the Triad AC adapter that I bought from JDS Labs along with my O2 and DAC separates?
 
Jun 20, 2013 at 1:00 PM Post #1,677 of 2,018
Quote:
jakejack_2008 said:
So, is it better than the Triad AC adapter that I bought from JDS Labs along with my O2 and DAC separates?
Click to expand...

 
The Triad they carry is the WAU12-200, so yes. The first number (12) is the AC voltage, and the second (200) is the max current in mA.
 
If you're drawing a lot of power from the amp, especially if your home wall voltage is a little low, the voltage into the O2 power supply might dip low enough in parts of the cycle that some significantly more noise could get through the regulators. However, the downstream electronics have very high power supply noise rejection ratios anyway, and to draw that kind of power you'd need to be driving some inefficient low-impedance headphones to loud volumes (like some of the planar magnetics). Maxing out the amp into say 600 ohms Beyers doesn't even draw much power, for example. Also, to draw that much power, you'd need to be listening at high enough volume that a little noise getting through is probably masked by the signal volume itself.
 
More or less, the other options are definitely better in some legitimate sense, but it's probably not relevant for most people and most headphones, and it shouldn't make much of a difference anyway. The WAU12-200 is just the default because somebody (somebodies) thought it was a good idea to skimp and save like $5. To be honest, I don't think I disagree, though this kind of thing is kind of anathema to the hi-fi crowd.
 
Jun 20, 2013 at 1:17 PM Post #1,678 of 2,018
AC Wall Transformer – There has been some confusion over the wall transformer and it’s a critical component. Most wall transformers put out DC but the O2’s power supply requires at least 13.5 volts AC. The ideal transformer would be rated at 14 - 16 VAC and 400 mA or higher. In North America the Triad WAU12-200 from Mouser is rated at 12 volts but is really about 13.5 VAC with no load, and on normal 120 volt line voltage works fine for anything but full power sine wave testing or driving rare low impedance power hungry cans. If your line voltage is below 117 VAC  or 235 VAC, and/or you plan to drive difficult low impedance headpones (i.e. HiFiMan planars), I would suggest a 14+ VAC transformer at 400+ mA. The best Mouser transformers are the WAU16-400, 412-218054 or WAU16-1000 CUI. But those are more expensive than the WAU12-200. The WAU20-200 also works for higher impedance headphones. At least some European 230 volt input 12 VAC output transformers only measure around 11.5 to 12 volts on normal line voltage and won’t work (especially if designed for halogen lights). You can also change the power jack to a 5.5mm x 2.5mm version if needed to match the plug of different wall transformers.
 
A.
 
Jun 20, 2013 at 6:17 PM Post #1,680 of 2,018
I have all the noted ac to ac adapters as well and have listened to a wide variety of headphones and can not tell any real difference in any of them.
 
I also have tested with batteries vs AC to AC and ditto..
 
A.
 
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