[headwhacker]

  Regarding power adapters, I am a little bothered. My unit came with a 12VAC, 500mA adapter, but I thought I have read somewhere that the minimum voltage was 13.5V (JDS?). They do recommend a 12VAC adapter nevertheless, which makes it even more confusing.
I bought a 18VAC adapter in the end but couldn't tell the difference in volume when I kept the knob fixed and swapped adapters. Is this right? Or is the 18VAC going to provide better voltage swings, slew rates, etc?
Thanks!

No it will not make any difference, except wasted energy by releasing more heat and sucking more power from the power line than what O2 needs.

 

[K_19]

Hey all,
 
Had a question about this combo in regards to powering the Q701, K701/2 series of headphones. What is the range of volume that is usable when using those headphones under the 1x gain? So for most modern tracks, what position on the volume knob is everyone at for decent volumes? This would be mainly used only through ODAC USB and rarely (if ever) any other sources, so mainly concerning the volume position it's being used with the usb/full 2v line output from the dac. Most of the tracks used would be mostly just modern recordings, although there are a few classical/lower mastered tracks that may need some more volume than those. Just trying to see which gain settings would be the best as as there is a used unit I'm looking at which has 1x and 5x gain settings... while I'm sure 5x gain would certainly be way too high for these I'm not so sure about the 1x.... 
 
Thanks in advance.

 

[headwhacker]

  Hey all,
 
Had a question about this combo in regards to powering the Q701, K701/2 series of headphones. What is the range of volume that is usable when using those headphones under the 1x gain? So for most modern tracks, what position on the volume knob is everyone at for decent volumes? This would be mainly used only through ODAC USB and rarely (if ever) any other sources, so mainly concerning the volume position it's being used with the usb/full 2v line output from the dac. Most of the tracks used would be mostly just modern recordings, although there are a few classical/lower mastered tracks that may need some more volume than those. Just trying to see which gain settings would be the best as as there is a used unit I'm looking at which has 1x and 5x gain settings... while I'm sure 5x gain would certainly be way too high for these I'm not so sure about the 1x.... 
 
Thanks in advance.

 
The range of the volume knob will depend on the headphone load impedance and sensitivity. Set the gain to 1x/3.5x if you are using ODAC as the source.

 

[K_19]

   
The range of the volume knob will depend on the headphone load impedance and sensitivity. Set the gain to 1x/3.5x if you are using ODAC as the source.

 
I'm thinking that'd be the most ideal setting as well, but the used unit I'm looking at (at a very good price) has the gains set at 1x and 5x (It's from Epiphany Acoustics), so just wondering how much range the 1x would have for the K's as I know 5x is impractical with ODAC as source (And I'm not so sure whether it's as straightforward to mod that particular gain setting to something else since it's not the stock 2.5x/6x gain, which is easy as clipping resistors).  

 

[MrKazador]

Regarding power adapters, I am a little bothered. My unit came with a 12VAC, 500mA adapter, but I thought I have read somewhere that the minimum voltage was 13.5V (JDS?). They do recommend a 12VAC adapter nevertheless, which makes it even more confusing.
I bought a 18VAC adapter in the end but couldn't tell the difference in volume when I kept the knob fixed and swapped adapters. Is this right? Or is the 18VAC going to provide better voltage swings, slew rates, etc?
Thanks!

Taken from the blog

. 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.

 

[sanakimpro]

Taken from the blog

. 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.

Thanks! Mine is a Beyerdynamic T1, DT 770/80, DT 880/250 and Custom One Pro. Figure if any of them requires the 14+ VAC?
Much appreciated!

 

[castleofargh]

are we seriously down to decide what VAC should be used for what headphone?
hey my laptop uses 20V, maybe I should put 30V to get it go faster, and directly into 220V it would be crazy good

. just be happy that the O2 doesn't blow up in your face when not using the recommended products.
 
 
 
 
 
for those with very little electric knowledge that are concerned about power requirements for headphones vs amps, download the excel stuff(click on the picture at the bottom) http://www.apexhifi.com/specs.html 
you just enter the values of your headphone and how loud you want to go, and by changing the loudness you can see how it affects the voltage and learn what to expect from different sources.
 
also useful for gain, find out how voltage variations translate into db("calculator free" method) http://www.sengpielaudio.com/calculator-gainloss.htm

 

[DIscoYou]

With the Epiphany Acoustics O2Di (Amp & DAC) does anyone know how the headphone and DAC outs switch? Is it a case of the RCAs only being live when there are no headphones plugged in?
 
http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2di-desktop-headphone-amplifierdac-3/

 

[KeithEmo]

There are two things you should know....
 
First, virtually all solid state headphone amps have a gain that is set by the circuitry (and you can vary it with the volume control). Likewise, things like slew rate aren't likely to change much as long as it's operating "within normal limits"). This means that changing the supply voltage a little is NOT going to change the amount of volume you get with a particular setting. In general, the only thing it will alter significantly might be the maximum output level you can get before it clips. (The gain will be exactly the same, but, with the lower supply voltage, it will "run out of steam" at a slightly lower level. If the supply voltage gets too low, you may simply reach a point where the amp can't make any usable output before it starts to distort.)
 
You should consider the manufacturer's recommendations because, depending on the exact circuitry they used, a voltage that is much too high can make the unit run very hot - or just plain burn it out (most components will just run a little bit hotter as you raise the voltage, but, at some point, many will just plain die), and an amp that clips sooner will sound "rougher and less dynamic".
 
Second, when you have a device that uses an AC adapter that PUTS OUT AC, that means that most of the power supply - the rectifiers and regulators - is inside the device itself. When an AC voltage is rectified, you end up with a DC voltage more or less proportional to it (and about 1.5x as much). This voltage is them smoothed by filter capacitors, and then usually smoothed more perfectly by a regulator. In the process of smoothing the signal, the regulator loses some voltage - typically 1 or 2 V - so you need more voltage going into the regulator than you're asking it to put out. In fact, most small AC adapters are somewhat "soft" in terms of what voltage they put out - their output varies depending on how much current you draw from them and how heavy the power supply itself is. A typical adapter rated "15VAC @ 500 mA" probably really puts out around 17 VAC @ 0 mA, and maybe as low as 10-12 VAC @ 500 mA. Another, bigger adapter, rated at "12VAC @ 2 Amps" may put out 14 VAC @ 0 mA, 13.5 VAC @ 500 mA, and 12 VAC @ 2 Amps. In this  case, the bigger power supply is actually putting out MORE voltage at 500 mA than the smaller one rated for the higher voltage.
 
AC power supplies that put out DC voltage are different, and fall into three major groups. Two of them (linear regulated and switch mode regulated) put out pretty much the same voltage regardless of the current you draw until you reach their limit - at which point the voltage drops suddenly or is shut off entirely. The third type (unregulated) acts like I described above, and has a voltage that drops lower as you increase the current you draw (and, again, heavier units can deliver more current with less of a drop in output voltage). 
 
If you received a unit, and it came with a power supply, then you should assume that the folks you bought it from made sure that the one they included exceeds the required amount of voltage and current required to work properly... and that adding a bigger one or one at a higher voltage is probably unnecessary and not especially beneficial. (When they told you what one to use, they were probably being conservative; that way, as long as you bought one that met those ratings, they were sure it would work properly.)
 
Quote:

  Regarding power adapters, I am a little bothered. My unit came with a 12VAC, 500mA adapter, but I thought I have read somewhere that the minimum voltage was 13.5V (JDS?). They do recommend a 12VAC adapter nevertheless, which makes it even more confusing.
I bought a 18VAC adapter in the end but couldn't tell the difference in volume when I kept the knob fixed and swapped adapters. Is this right? Or is the 18VAC going to provide better voltage swings, slew rates, etc?
Thanks!

 

[adydula]

1. 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.

 

[lerad]

Good Day! i have o2/odac combo from jds labs and planning to get hd650 or he400i, can o2 bring out the best sound on both headphones i mentioned or does it pair well?

 

[dazzerfong]

  Good Day! i have o2/odac combo from jds labs and planning to get hd650 or he400i, can o2 bring out the best sound on both headphones i mentioned or does it pair well?

If by 'best' you mean 'just louder' and, depending on your source, less noise/distortion, yes. If by 'synergy', that depends on your preference of sound.

 

[diamondears]

Good Day! i have o2/odac combo from jds labs and planning to get hd650 or he400i, can o2 bring out the best sound on both headphones i mentioned or does it pair well?

Yes. It doesn't color or tweak the sound coming from the source nor coming out of the HP though.

 

[lerad]

  If by 'best' you mean 'just louder' and, depending on your source, less noise/distortion, yes. If by 'synergy', that depends on your preference of sound.

Thanks! i listen to all kinds of music genres. if you can recommend me a amp/dac combo price range $200-$300 what would it be? for hd650 or he400i

 

[lerad]

  Thanks! i listen to all kinds of music genres. if you can recommend me a amp/dac combo price range $200-$300 what would it be? for hd650 or he400i

 
 

Yes. It doesn't color or tweak the sound coming from the source nor coming out of the HP though.

Thanks