O2 AMP + ODAC - Page 33

this ?

 

http://dx.com/p/fiio-l2-standard-3-5mm-male-to-3-5mm-male-cable-10cm-length-65664

Yeah one of those. I just checked Amazon for one of those and it's $3. XD

Thanks for the suggestion! :D

 

The E9 has much higher output impedance on the 1/8" jack, and that causes the voltage on the low impedance Q701 to drop by about 3 dB more.

hi, i have a question about the power supply for the o2...

 

is a 13v, 800mA wall wort sufficient for charging the o2?  i know the jds site and the designer's site say, '14-20v'... but i was wanting to double check with other head-fi'ers.  

 

cheers

13v  is not enough

JDS Labs actually ships the O2 with a 12 V/200 mA adapter by default. A 13 V/800 mA one is probably enough if you do not use headphones that need a lot of current, and it actually outputs 13 Vrms with a 800 mA load.

The 12 VAC adapter sold for the O2 outputs 13.9V @200mA, which meets spec.

 

Check the actual output rating on that adapter. The 800 mA is more than enough, but you may or may not be below the 14-20V spec.

So, how much voltage does that "13 V" adapter output ? If it is 13 Vrms with a 800 mA load (and thus more than 13 unloaded), then it would be OK.

 

It's a step-down transformer, so the output voltage depends on the input voltage.

 

Is it rated at 13V for a 120V input? What is your line voltage?

It is not my transformer, so I do not know the details. Maybe ayres can provide the information (it would be best to simply measure the voltage with a DMM if the adapter has already been bought).

 

Oops, quoted the responder and not the OP. Sorry.

The power circuit of the O2 requires an AC input that exceeds 12V plus any junction drop of the linear regulator IC's. Generally, I'd say anything over 13 volts will likely be okay. Of course you'll also need to make sure it outputs enough current (200mA should suffice, but it wouldn't hurt to get a 400mA+ one, just in case) 

thanks for the responses... here's a pick of the stats:


if the image doesn't embed, I'll have to try again later.

 

That is not entirely accurate, here is a simplified simulation of the power supply (the diodes are not the same as those used in the O2, but the simulator does not have the 1N4002, so I replaced it with whatever I could find with similar specs):

 

 

The voltage of the AC/AC adapter is specified as RMS voltage, but rectifying that results in DC voltage that is square root of 2 (~1.4142) times higher, minus the 0.6-0.7 V drop on the diodes. Of course, under load it drops further because the capacitors discharge, and the transformer has non-zero resistance as well. The 18 V peak voltage shown on the circuit translates to 12.73 Vrms, and the Rser=1 decreases that by an additional few tenths of a Volt (the green trace on the graph is the output of the transformer, and it has about 17.5 V peaks). The regulator ICs have a voltage dropout of about 2 V, but it may vary with the exact model used; the +/- 14 V minimum voltage (red and blue traces) is just enough to prevent the power supply from falling out of regulation. The 2*100 Ω resistors simulate a DC load of 140+ mA, that is probably enough for not too demanding headphones and the rest of the amplifier. So, I think if the transformer can output at least 13 Vrms even under worst case conditions, then that will work if the headphones do not need a lot of current.

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.