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O2 AMP + ODAC - Page 34

post #496 of 3410
Quote:
Originally Posted by ayres View Post

pardon the ignorance, but my assumption is that the rating of the transformer will determine the rate at which the batteries recharge - not which headphones the o2 can and cannot drive. but I imagine that if listening while recharging, an insufficient psu could result in a slow battery drain. if an insufficient transformer just means that it takes a little longer to recharge, then the concern is less of a concern, but if the batteries/circuitry could be damaged over time, then there is a concern.
I'm using the o2 with 32 & 300 ohm cans.

Check the circuit (click for legible size, please excuse the quality):


Each battery is charged by the output of the respective regulator (7812 for positive and 7912 for negative), through a diode and the 220 ohms resistor. The regulator output would have to be really really low (+12V regulator outputting less than the battery voltage, almost, i.e. waaaaaay out of regulation), for the battery to actually be powering the amp.

Rate of charging just depends on the regulator output (should be about +12V, -12V) and current battery level. It pretty much just charges as according to what you see in the circuit and Ohm's Law: (Regulator output voltage - diode drop voltage - current battery voltage) / 220 ohms is the trickle charging current. That's not related to the AC adapter rating, except unless it's far below the point where the regulator output voltage is significantly affected.

As for the voltage the regulators receive (needs to be a certain point like 2V above +12V or so, or however much the drop is), that depends on the AC line voltage, transformer, how much the capacitor discharges between cycles on the AC input. Capacitor discharge between cycles depends on current drawn by the amp, thus the discussion about how much power is being used, which in turn depends on what headphones you're using and how loud you're listening and whether or not you're charging the battery, etc.
post #497 of 3410

The WAU16-400 is the best transformer for any headphone with the O2.

 

Alex
 

post #498 of 3410
Quote:
Originally Posted by adydula View Post

The WAU16-400 is the best transformer for any headphone with the O2.

 

Alex
 


K - Why?

 

The O2, from what I understand, is either railed to +-9V on battery, or +-12V plugged in. How does the extra current and power help anything?

post #499 of 3410
Quote:
Originally Posted by MrMateoHead View Post

Quote:
Originally Posted by adydula View Post

The WAU16-400 is the best transformer for any headphone with the O2.

 

Alex


K - Why?

 

The O2, from what I understand, is either railed to +-9V on battery, or +-12V plugged in. How does the extra current and power help anything?

 

See Post #375 and Post #390 in this thread for an analysis of transformer requirements.

 

Here's the conclusion.

 

What it all boils down to is a 14Vac - 16Vac transformer with a 400mA or greater secondary rating (like the WAU16-400) means not having to know any tech details about the whole thing. It will just work, with the one exception of using a low impedance headphone that is also low sensitivity, that might pull more than 56mA per channel. Then use a 14Vac - 16Vac 1000mA unit, like the WAU16-1000 which is only $0.25 USD more anyway at Mouser ($11.50 USD vs. $11.75). Might as well just get the 1000mA unit if there is plug space - it is about 25% larger physically.

[emphasis added]

post #500 of 3410

We cant link directly to where this is posted but you can easlily find if if you search.

 

That said the AC transformer is a critical component. The O2's power supply needs at least 13.5 volts AC.

The ideal AC transformer would be rated at 13-16 VAC and 400 ma or higher.

 

The Mouser Triad WAU-12-200 is rated at 12 volts but is really about 13.5 VAC with NO LOAD and with a 120VAC line voltage works just fine for anything but FULL power sine wave testing OR driving LOW impedance power hungry cans. I have actually measured the no load AC voltage and its 13+ volts but varies with the line voltage flucuations.

 

If you line voltage is actually below 117 VAC and/or you plan to drive difficult low impedance cans (likek HiDiMan planars) ...a 14+ VAC transformer at 400+ ma is suggested. The covers the worse case both for line voltage and low impedance cans....

 

The best Mouser transformers are the WAU16-400, 412-218054 or WAU16-1000 CUI. But those are more expensive than the WAU12-200.

 

Having a AC transformer that provides a 13.5 VAC no load is right on the edge of letting some ripple through under the worst case conditions.....so if your O2 is used with low line voltage, for serious sine wave testing, continous tones, or using lower impedance power hungy cans having a higher voltage AC supply is highly recommended.

 

I have the 12-200 and the 18-500 and do not hear any real world difference in listening with AKG 701/2's, LCD2's, Grado 325i's.

 

Again there is more technical details on the other site...do a search and do some reading...

 

Alex


Edited by adydula - 12/5/12 at 4:31pm
post #501 of 3410
Quote:
Originally Posted by adydula View Post

Having a AC transformer that provides a 13.5 VAC no load is right on the edge of letting some ripple through under the worst case conditions.....so if your O2 is used with low line voltage, for serious sine wave testing, continous tones, or using lower impedance power hungy cans

So is the stock JDSlabs wallwart good enough for the HD650?

edit: I just noticed its fine according to nwavguy, supposedly a larger voltage ac adapter is if you want to run hifiman cans etc., otherwise it just makes the regulators run hotter...
Edited by muad - 12/5/12 at 6:19pm
post #502 of 3410
Quote:
Originally Posted by muad View Post
So is the stock JDSlabs wallwart good enough for the HD650?

edit: I just noticed its fine according to nwavguy, supposedly a larger voltage ac adapter is if you want to run hifiman cans etc., otherwise it just makes the regulators run hotter...

 

The WAU12-200 was always good enough for my HD-650, Fosxtex T50RP, and Beyerdynamic DT 990 and T70. One last problem is when the line voltage is 'low'. At work, occasionally our voltages dip quite low. Our Plant Manager. says sometimes they measure 105VAC at a few outlets. I've heard no audible effects from whatever's happening in the building, but I bought a Big Boy just in case.

 

When the input voltage to the O2 is raised, say from ~12V to ~16V, more heat is generated. There's no supposition about this. Personally, I may just be reducing the useful life of the O2, but hopefully it isn't by much. I haven't lost any sleep yet.

post #503 of 3410

thanks for the responses... @ hamilcarbarca, i saw those older posts in the upper half of the 300s, and very insightful regarding my psu question.

 

b/c the o2 is diy conceived, we are, in a way, left to preference - both objectively and subjectively.

 

i do have a lingering questions, though.  if battery charging is happening when the amp is NOT in use, then does it really matter which transformer is used as long as the batteries are receiving a full charge?

post #504 of 3410

additionally, are there sonic differences between the o2 when plugged in to a transformer vs running off the batteries?

 

cheers

post #505 of 3410

ayres...

 

I cant hear any differences between any of the transformers I have and just running off of batteries.....none, zip, zero, nada....

 

The reason I got the 18 volt AC transformer was I wanted to hear for myself if there were any real differences using a higher than 13.5 VAC transformer.

 

If I had to do it again the 16 vac version is what I would buy and use...

 

Alex

post #506 of 3410

So, I received my custom O2 a few days ago and it's awesome. Far better than my E9 IMO.

I went 47/0 with nothing but a Desert Eagle on MW3 using the O2 and a Q701.

 

 

700


Edited by Tus-Chan - 12/13/12 at 6:58am
post #507 of 3410

I have a set of Q701's that I really like, the most comfortable cans ever to me!

Alex

post #508 of 3410
Quote:
Originally Posted by rudi0504 View Post

dcb2a9fa.jpg

 

 

d9f8299d.jpg

 

JDS Lab ODAC usb DAC + JDS Lab O 2 head amp full modification with Black Gate Capasitors

 

that looks nice and all, but you really want it enclosed in metal to reduce noise

post #509 of 3410

Unless its a really noisy environment and next to electrical stuff he will most likely be ok..I ran one of my O2's and ODACs 'naked' and didnt have any interference or noise issues that I could discern...this is when i was doing current load measurments to see what the actual current draw was from the USB PC power..

 

Alex

post #510 of 3410
Quote:
Originally Posted by Tus-Chan View Post

So, I received my custom O2 a few days ago and it's awesome. Far better than my E9 IMO.

I went 47/0 with nothing but a Desert Eagle on MW3 using the O2 and a Q701.

 

 

700

Wow, are you naturally really good at video games? Or would you give a lot of credit to your Q701's?

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