[locksbury]

  I just bought the new O2 (the one with no battery and with RCA/ power/ input on the back) from headnhifi.com in Switzerland, because I live here.
i can make some photos if you want, but you can find them here http://www.headnhifi.com/O2-desktop-amplifier

I'm quite happy, this is my first headphone amp and I was skeptical: turns out the difference is quite noticeable. But onestly, I'm more surprised by how good it looks than its sound 

. Anyway, now my chain is complete and I'm happy of its sound.
I use it with the HE400 from hifiman.

I'm just curious of 2 things, I'm sure you can answer me.

1) Should i leave the jack in when I turn on the amp ? And when I turn it off? Should the volume be down to zero?

2) The Odac light is always on, even when my pc is off, will this ruin it? How do you turn it off?



And, just as a curiosity, for those of you that have the he400 with this amp, is 9'o clock a safe listening volume (with low gain). At what volume do you listen? I already have tinnitus on cold months (every year), I don't want to damage my earing  
 
 
thank you

1) As with any audio amplifier, to save any thump in your speakers/headphones and to save your own ears, especially if you accidentally left music playing and the volume is at full when you turn it on; you should always turn the control to minimum when turning it on or off. (Always was a good idea when I was doing stage crew at university!)
2) As it appears you bought the mains powered version of the amp/dac combo, I think the LED on the front is the power indicator for the O2 amp section only and the ODAC board inside is powered from the USB on your PC. So you should be fine.
 
HTH

 

[realityhas]

 
1) As with any audio amplifier, to save any thump in your speakers/headphones and to save your own ears, especially if you accidentally left music playing and the volume is at full when you turn it on; you should always turn the control to minimum when turning it on or off. (Always was a good idea when I was doing stage crew at university!)
2) As it appears you bought the mains powered version of the amp/dac combo, I think the LED on the front is the power indicator for the O2 amp section only and the ODAC board inside is powered from the USB on your PC. So you should be fine.
 
HTH

Thank you for your fast response

1) So, as long as i turn the volume down, I can leave the headphone jack inserted even when I turn it off ?

2) I bough the O2 amp separate from the Odac. The O2 amp light is on ONLY when i turn it on with the front button. But the ODAC led is on all the time, even when the PC is off. The ODAC is connected only via usb, and it has no buttons so i cant turn it off

 

[AsianBatman]

  Thank you for your fast response

1) So, as long as i turn the volume down, I can leave the headphone jack inserted even when I turn it off ?

2) I bough the O2 amp separate from the Odac. The O2 amp light is on ONLY when i turn it on with the front button. But the ODAC led is on all the time, even when the PC is off. The ODAC is connected only via usb, and it has no buttons so i cant turn it off

 
It's fine to leave your headphone jack in, the O2 is pretty good at not making that pop noise that ruin headphones like some tube amps. I got my ODAC from mayflower electronics and does not have a led on it. I'm assuming your PC is fairly new and most motherboards have "charging" future that allows phones and such to be charged while the PC is off. It is safe and I don't believe there is a way to turn it off. My Audio-gd light stays on when I turn my PC off also. 

 

[realityhas]

   
It's fine to leave your headphone jack in, the O2 is pretty good at not making that pop noise that ruin headphones like some tube amps. I got my ODAC from mayflower electronics and does not have a led on it. I'm assuming your PC is fairly new and most motherboards have "charging" future that allows phones and such to be charged while the PC is off. It is safe and I don't believe there is a way to turn it off. My Audio-gd light stays on when I turn my PC off also. 

 Yeah, I bought it this summer and it charges my phone too...

Thank you both very much

 

[adydula]

Some PCs allow for thu USB port to be available even when powered down. for charging devices etc like was said here in earlier posts.
If you want and have more USB ports you can try one that is not powered on.
 
Some laptops etc have both powered and unpowered USB ports and some can be changed in the BIOS. Check with your PC manufacturer of website/manual etc.
 
I don't think the ODAC being plugged in all the time and the light one really would hurt anything.
 
Good practice is to always turn down the volume when inserting or removing the headphone plug.
 
On my two O2 amps I usually turn down the volume, remove the plug and then turn it off. No thumps.
 
Even with the O2 amp volume all the way down there is still a small thump to be heard.....I have several sets of cans,
LCD2's, M50's, Grado 325is, AKG 701/702, Beyer DT 1350, Beyer T90's....none of them are harmed by this thump.
 
Here is something to think about as well: Someone asked: Is keeping the power supply on 24/7 and switching (on or off) the DC supply to the amps at board level will minimize the thumps.
 
The answer is yes and here are the cases to think about:
(This is from another post on another forum fyi...)
PM me if you want the link etc).
 
Case I:
You keep PS AC adapter ON 24/7 & use FP switch to turn amp ON/OFF-minimal thump.
 
Case II:
You turn AC adapter ON & use FP switch to turn amp ON/OFF-minimal thump (same as above).
 
Case III:
FP switch is in ON position & you turn ON AC adapter- Loud thump, worst case is AC half cycle.Even if you plan to keep AC power supply ON 24/7 there may be situation of momentarily supply failure (lasting just under a second) or brown outs resulting in large thumps. The batteries in O2 also act like "online UPS" to eliminate Case III type situation.C1(1uF) is also useful in reducing power ON thumps The "minimal thump" will still be more than O2 using standard BOM. BTW High impedance, low sensitivity h/p are more immune to power ON/OFF transients than low impedance, high sensitivity h/p e.g. IEMs.Other well designed desktop amps usually employ some sort of relay mechanism to connect h/p after the PS has stabilized & disconnect the h/p in case of supply failure/turn OFF/ DC at o/p type situation.
 
A.

 

[r010159]

On another note, I am having a bit of apparent trouble with my JDSLabs O2/ODAC combo. I have left the unit on for days. Recently, I have noticed that when music is played, I sometimes get some distortion , in particular with vocals reaching high frequencies. Now I think this may not be the O2/ODAC. But I am not sure. The distortion sounds like rapid krincking of the cellophane wrapper on a pack of cigarettes. So this is happening in the analog part of the signal chain. This means its either the O2 part, the headphones, or possibly some connection that is loose or incomplete between the headphones and the O2, like the headphone jack. The jack on the headphones is a little dhort and may not be making a good connection I am just guessing here. What is interesting is that this problem can disappear, even at higher volumes. But I had turned the unit off for some time. So this may be temperature related.

Also, music can be intermittent. Part of the reason is the audio file. Another cause is when my poor Intel Duo is apparently being overtaxed when I am doing something else on the computer. There alao was a previous problem with iTunes doing this. So I need to look into this problem further.

 

[MrMateoHead]

On another note, I am having a bit of apparent trouble with my JDSLabs O2/ODAC combo. I have left the unit on for days. Recently, I have noticed that when music is played, I sometimes get some distortion , in particular with vocals reaching high frequencies. Now I think this may not be the O2/ODAC. But I am not sure. The distortion sounds like rapid krincking of the cellophane wrapper on a pack of cigarettes. So this is happening in the analog part of the signal chain. This means its either the O2 part, the headphones, or possibly some connection that is loose or incomplete between the headphones and the O2, like the headphone jack. The jack on the headphones is a little dhort and may not be making a good connection I am just guessing here. What is interesting is that this problem can disappear, even at higher volumes. But I had turned the unit off for some time. So this may be temperature related.

Also, music can be intermittent. Part of the reason is the audio file. Another cause is when my poor Intel Duo is apparently being overtaxed when I am doing something else on the computer. There alao was a previous problem with iTunes doing this. So I need to look into this problem further.

Check your "buffer" settings on your audio player. I had stuttering with Foobar until I set a pretty high buffer (like a full 1 second).
 
Surest solution for the static problem:
1) Download Audacity
2) Drag and drop audio file with static into audacity window
3) Select View > Show Clipping
4) Notice the presence or lack of the color red
 
What you are hearing is the O2/ODAC playing back the Clipped audio present in the recording itself. The resolution of the thing is so damn high, it can actually do this. I thought my headphones were going bad when I started noticing it. Generally speaking however, it has more to do with the overly "Hot" (compressed) recordings that have been put out over and over again into the world. I am sorry to say that there is no real cure for it. Sometimes you can get lucky and there is another version of the recording to check out. But, generally, the clipping is at the recording level so it is beyond control.
 
Interestingly, I usually see clipped vocals if the artist is a female. Clipped music is usually in the rock / metal recordings as they assume that no dynamic range is awesomer than some dynamic range. Pop recordings are usually well done because I think there is more money to spend getting it right. Garage bands seem to try to save a few bucks and boy, it can really ruin an otherwise great album.

 

[r010159]

I thank you for you reply. This sounds like the problem The specific instance I remember is with female vocals. Next time I hear it, I will put it through Audacity. The O2/ODAC combo is turning out to be a real good purchase of mine!


EDIT:

PS: What is the difference between the headphone input and the line input? Also, is the higher gain setting really a bass boost?

 

[jring]

  I thank you for you reply. This sounds like the problem The specific instance I remember is with female vocals. Next time I hear it, I will put it through Audacity. The O2/ODAC combo is turning out to be a real good purchase of mine!


EDIT:

PS: What is the difference between the headphone input and the line input? Also, is the higher gain setting really a bass boost?

 
Hi,
 
the O2 should have a Line-In and a Headphone-Out. The ODAC just has a Line-Out, sometimes not even that if it is integrated in the same enclosure as the amp.
 
The gain switch does not boost the bass but switches the amp to a different and usually higher voltage gain. This is for sources with a low input voltage like a cellphone and with the default 6.5x with pressed gain switch and an ODAC as a source, the amp will clip regardless of the volume pot setting if the digital volume is at 100%.
 
Joachim

 

[ShenaRingo326]

Hi,

the O2 should have a Line-In and a Headphone-Out. The ODAC just has a Line-Out, sometimes not even that if it is integrated in the same enclosure as the amp.

...

Joachim

Actually if you have the JDS labs o2+odac combo, when the o2 amp power is off, the line in jack functions as the line out of the odac, so you can connect it to another amp.

When the o2 power is on, the line in jack functions as the line in for the o2 amp, and you can actually send signals to the o2 at the same time from both odac and line in.

 

[locksbury]

Now that my O2+ODAC DIY parts are on order from headnhifi.com, I can't wait to see what new detail in my music I discover with my Grado SR-60s.

 
In the meantime I have questions:
 
a) Most of my music collection is sampled at 16/44.1, but I understand DVDs are at 16/48 and I recently got some 24/96 tracks (only cause they were free), so would it be best to set the ODAC to rates to 24/96 and let the OS do any re-sampling as required?
 
b) I'm going to use the amp/dac combo across all my PCs (win7 gaming rig, mac mini and linux laptop). Has anyone used the ODAC with linux?

 

[Dano91]

  I thank you for you reply. This sounds like the problem The specific instance I remember is with female vocals. Next time I hear it, I will put it through Audacity. The O2/ODAC combo is turning out to be a real good purchase of mine!


EDIT:

PS: What is the difference between the headphone input and the line input? Also, is the higher gain setting really a bass boost?

It's not a bass boost and you really shouldn't be using higher gain with ODAC (only in special circumstances), because it can make distortions / clipping. The problems you described earlier sounds just like that to me.
Higher gain is meant to be used with low power devices like mobiles etc..

 

[jring]

  Now that my O2+ODAC DIY parts are on order from headnhifi.com, I can't wait to see what new detail in my music I discover with my Grado SR-60s.

 
In the meantime I have questions:
 
a) Most of my music collection is sampled at 16/44.1, but I understand DVDs are at 16/48 and I recently got some 24/96 tracks (only cause they were free), so would it be best to set the ODAC to rates to 24/96 and let the OS do any re-sampling as required?
 
b) I'm going to use the amp/dac combo across all my PCs (win7 gaming rig, mac mini and linux laptop). Has anyone used the ODAC with linux?

 
I'm listening to it atm on my laptop with ubuntu 12.04 lts. Works out of the box as with all other linux systems with usb audio drivers... I also have it at my goflex nas with debian sometimes...
 
About bit depth and sample rate, people are bound to disagree... after all resampling and multiplying is not exactly bit-perfect... that being said I'm lazy and use it on 24bit default (and whatever sample rate the file has) so I can use soft-volume without loosing resolution.
 
Joachim

 

[jring]

Actually if you have the JDS labs o2+odac combo, when the o2 amp power is off, the line in jack functions as the line out of the odac, so you can connect it to another amp.

When the o2 power is on, the line in jack functions as the line in for the o2 amp, and you can actually send signals to the o2 at the same time from both odac and line in.

 
Ouch, two sources working against each other sounds - not such a good idea... mine is self built from a head'n'hifi kit and I used the switched input jack to connect ODAC to O2 only when no plug is in.
 
I'll probably put on the 3.5mm smt jack on the pads on the ODAC board and drill a hole in the backplate as line-out but then one would have to put a blank jack inside the line-in in order to open the connection to O2 when using ODAC alone (especially with the amp off one would not like its inputs in the circuit). Or I need to find a 3.5mm switched stereo jack in SMT and a similar pad layout as the one used in ODAC... I actually found one some time ago after long googling but available in quantities only
 
Joachim

 

[r010159]

It looks like I damaged my unit. I went to get up and walk away from the desk, still within reach of the line to my headphones. I did not know it, but the chord was wrapped around my foot. This ended up yanking the unit off the desk and disconnecting the USB cable. This twisted the socket of the microUSB and broke it off to roll around inside of the unit.

I contacted JDSLabs and they quickly replied, like within an hour. I need to ship the unit in for repair. If the unit cannot be repaired, they will sell me a discounted DAC board. I hope this will not take long.

Bob Graham

EDIT:

I will keep everyone informed how JDSLabs handles this problem.