Yes, yes, and probably not.
The gap that small wire causes in the front panel seating isn't too noticeable. You need to solder the wire to the ground pin of the input jack, which is the jack closest to the edge of the board. The ground pin is the one right on the center line of the jack underneath, closest to the hole the plug goes into. I wasn't sure if JDS was pre-soldering a wire there already. Sounds like not. You might want to have a chat with them too. Seems like it kind of defeats the purpose of having the board assembled if you have to do some more soldering.Yes, yes, and probably not.
Makes sense, thanks. Yeah actually JDSlabs sent it out and it should be here sometime this week. I just wanted to make sure I didn't need to order anything aside from the assembled PCB, enclosure, front panel and charger. It may come with a wire already soldered on but it's good to know just in case it isn't. Otherwise I would've just used it without.
RocketScientist;2845023Those advocating higher output impedance and/or other "creative" output designs have virtually nothing supporting their claims. They don't have any credible measurements or blind listening tests. While it's certainly possible some might prefer the generally less accurate sound of some headphones driven from such a source said:
@regal, I plan to do some similar measurements to Benchmark's comparing driving resistive loads with driving real headphones. With the O2 it won't make much difference, but with some amps (as Benchmark has shown) it can make a substantial difference.
As for the subjective side, that's what blind A/B testing is for. That's why I set the O2 up against my DAC1 Pre and let several people listen with a variety of headphones and music. Nobody could tell them apart.
If there are significant "intangible" differences between headphone amps that measure well, they're so subtle mere mortals even with very careful listening using high-end headphones, cannot hear them when you remove the knowledge of which amp is playing. If you conduct a blind test between the O2 and an amp with a much higher output impedance you are likely to hear differences. And those differences can be easily measured.
For headphone amps, the measurements I'm already making are sufficient to predict if the amp is sufficiently transparent. See:
InnerFidelity Headphone Amp Measurements
and
Music vs Sine Waves
The above articles go into much more detail but I still plan at least another article or two on measurements, testing, etc.
As for the subjective side, that's what blind A/B testing is for. That's why I set the O2 up against my DAC1 Pre and let several people listen with a variety of headphones and music. Nobody could tell them apart.
If there are significant "intangible" differences between headphone amps that measure well, they're so subtle mere mortals even with very careful listening using high-end headphones, cannot hear them when you remove the knowledge of which amp is playing. If you conduct a blind test between the O2 and an amp with a much higher output impedance you are likely to hear differences. And those differences can be easily measured.
For headphone amps, the measurements I'm already making are sufficient to predict if the amp is sufficiently transparent. See:
InnerFidelity Headphone Amp Measurements
and
Music vs Sine Waves
The above articles go into much more detail but I still plan at least another article or two on measurements, testing, etc.
That's why I follow this product. Even though I probably couldn't hear much difference between gear that measures only mediocre, having something that measures very well ensures room for some source-based imperfections to not push the whole experience past my threshold.
I have noticed something interesting, though. If I do A/B on gear, even when I do it sighted, I often can hardly distinguish much difference in certain cases. But if I listen exclusively to one of the pieces for a few days, switching to the other is a more dramatic experience than the A/B let on. So there's a certain amount of familiarization that occurs that I'm trying to figure out how to debunk (easy) or legitimize (difficult) and even use in a valid way to test gear. I don't know if it's possible, but it's going through my head.
The other thing I wonder about is the accuracy of some of InnerFidelity's and HeadRoom's test charts, particularly in the realm of distortion and square wave response. The measurements occur from a HeadRoom balanced amp. I don't know how well that measures. It's probably pretty good, but having seen Benchmark's document showing how poorly, well... how differently headphones can react to even low-ish impedance loads, I'm beginning to wonder if more parts of the whole experience need to be evaluated and rethought.
I have noticed something interesting, though. If I do A/B on gear, even when I do it sighted, I often can hardly distinguish much difference in certain cases. But if I listen exclusively to one of the pieces for a few days, switching to the other is a more dramatic experience than the A/B let on. So there's a certain amount of familiarization that occurs that I'm trying to figure out how to debunk (easy) or legitimize (difficult) and even use in a valid way to test gear. I don't know if it's possible, but it's going through my head.
The other thing I wonder about is the accuracy of some of InnerFidelity's and HeadRoom's test charts, particularly in the realm of distortion and square wave response. The measurements occur from a HeadRoom balanced amp. I don't know how well that measures. It's probably pretty good, but having seen Benchmark's document showing how poorly, well... how differently headphones can react to even low-ish impedance loads, I'm beginning to wonder if more parts of the whole experience need to be evaluated and rethought.
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@ethanolson, I agree on most counts, but the "longer listening period" argument has been pretty well debunked by published studies. In one AES study, they sent members of an audiophile club home with sealed "black boxes" where some altered the sound and some did not. They asked them to spend a week or two listening to their box and then decide if they had a "straight wire" box or one that degraded the sound.
They also ran blind ABX testing with the same boxes. The outcome was very telling. The blind ABX testing allowed the listeners to easily pick out the boxes that degraded the sound. But when they took a box home for a week, nobody guessed better than randomly as to which kind of box they had.
The end result is that study, and others, have demonstrated A/B testing is more sensitive supposedly because we humans cannot remember subtle audio details very well. So the shorter the time between comparing two things, the easier it is to detect differences.
I may have provided a link to the above paper in my Subjective vs Objective article. If not, I can dig it up if you're interested.
And, from another perspective, there are well documented examples of high-end audio systems being altered in ways that should be easily audible (by audiophile standards) yet the owners don't notice any difference when they're unaware of the change despite lots of extended listening. An example is adding an A/D and D/A into the signal path of an all analog vinyl system owned by someone who strongly dislikes anything digital. Despite the "nasty" digital hardware hidden away, their system sounds as great as ever when they think the signal path is pure analog.
They also ran blind ABX testing with the same boxes. The outcome was very telling. The blind ABX testing allowed the listeners to easily pick out the boxes that degraded the sound. But when they took a box home for a week, nobody guessed better than randomly as to which kind of box they had.
The end result is that study, and others, have demonstrated A/B testing is more sensitive supposedly because we humans cannot remember subtle audio details very well. So the shorter the time between comparing two things, the easier it is to detect differences.
I may have provided a link to the above paper in my Subjective vs Objective article. If not, I can dig it up if you're interested.
And, from another perspective, there are well documented examples of high-end audio systems being altered in ways that should be easily audible (by audiophile standards) yet the owners don't notice any difference when they're unaware of the change despite lots of extended listening. An example is adding an A/D and D/A into the signal path of an all analog vinyl system owned by someone who strongly dislikes anything digital. Despite the "nasty" digital hardware hidden away, their system sounds as great as ever when they think the signal path is pure analog.
Well that saves me a bunch of time. Thank you. I've already got it nailed for the clearly audible realm (such as a different make of headphones), so this covers the threshold territory.
Hearing does adapt... and rather quickly as well. I worked on that theory and found that my own ears adapted to most changes in "coloration" in under a minute. It's amazing how a cheap pair of airline "clippies" can sound great after a while. Fortunately, that allows me to be fine with my sub-awesome IEMs when I'm on the road. After a couple minutes, I don't know what I'm missing anymore.
Hearing does adapt... and rather quickly as well. I worked on that theory and found that my own ears adapted to most changes in "coloration" in under a minute. It's amazing how a cheap pair of airline "clippies" can sound great after a while. Fortunately, that allows me to be fine with my sub-awesome IEMs when I'm on the road. After a couple minutes, I don't know what I'm missing anymore.
That doesn't work quite as well with non-negligible levels of external noises intruding though. Fortunately Rockbox has a fairly useful EQ.
Oh, and we've had a case of a pre-built O2 going dead on another forum. Apparently it still emit emits power-up and power-down thumps, but nothing else happens, not even the LED is lit. I hope we can get this fixed over here instead of it having to be sent back over the pond.
Oh, and we've had a case of a pre-built O2 going dead on another forum. Apparently it still emit emits power-up and power-down thumps, but nothing else happens, not even the LED is lit. I hope we can get this fixed over here instead of it having to be sent back over the pond.
@sgrossklass, I'm happy to try and help out if I can. If the LED is not even lighting up I would be surprised if it's emitting normal power on/off noises.
Perhaps it's been running from battery rather than AC and was left on for an extended period and the batteries have gone dead?
The LED is right after the power switch and should at least faintly light up if there's enough voltage to operate the op amps. It will still light up even if one of the supply rails is shorted to ground. If the amp is not working on AC or battery that likely rules out any power supply problem.
There's quite a bit in the Trouble Shooting section if someone with a DMM can have a look at the board.
Perhaps it's been running from battery rather than AC and was left on for an extended period and the batteries have gone dead?
The LED is right after the power switch and should at least faintly light up if there's enough voltage to operate the op amps. It will still light up even if one of the supply rails is shorted to ground. If the amp is not working on AC or battery that likely rules out any power supply problem.
There's quite a bit in the Trouble Shooting section if someone with a DMM can have a look at the board.
hi all - can someone either direct me to, or explain preferebly with photos exactly how to lower the gain on my O2 by "clipping resistors"?
I should warn you that I am very inexperienced with anything diy beyond making cables.
I am using the O2 with My LCD-2's and find that i almost never move the volume past 9 o'clock which gives me an average spl of about 73db's and 80db peaks according to my spl meter iphone app (which actually seems pretty accurate). It would be nice to have more volume play, as well as the fact that my soon coming 16ohm customs will almost certainly be too loud with even less volume play at the current low gain setting on the amp.
by the way if there is any to do this that would be reversible without soldering, that would be great too... just in case.
thanks!
I should warn you that I am very inexperienced with anything diy beyond making cables.
I am using the O2 with My LCD-2's and find that i almost never move the volume past 9 o'clock which gives me an average spl of about 73db's and 80db peaks according to my spl meter iphone app (which actually seems pretty accurate). It would be nice to have more volume play, as well as the fact that my soon coming 16ohm customs will almost certainly be too loud with even less volume play at the current low gain setting on the amp.
by the way if there is any to do this that would be reversible without soldering, that would be great too... just in case.
thanks!
If you cut the marked ones low gain will become 1x, the absolute maximum when using sensitive IEMs, even from a modest source as a Clip or iPod.
Clip just one lead and you should be able to rectify it on a later occasion. Just bend the resistor slightly away, maybe tuck it in some tape. It shouldn't do any harm.
Have you opened it?
If the resistors are socketed (don't know if JDS is doing this) you do exactly the same, except for lifting instead of cutting the resistors, of course.
That currently is the main problem.
So far, visual inspection showed that the traces going from Q1/2 to C8/9 may be damaged. That would explain missing power for sure. Otherwise there are a few suspect-looking solder joints to be seen on photos (at least 3 so far), including U2 pin 3. Still not sure why the LED wouldn't be lit.
There has actually been at least one case of a bad LED (open) in the past toubleshooting posts. I think there was even a second. See if they can carefully measure between pins 4 and 5 on U2. If they get the full 24Vdc (ac) or 17Vdc (batts) then that LED is open, of course. If they measure zero volts between 4-5, measure across R6. If the full voltage is there the LED is shorted. Whatever voltages they measure please post back - would probably help RocketScientist to debug it.
Either way a defective LED would confuse the power management circuit and could produce thumps at odd times.
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Does anyone know how much voltage the sansa clip+ puts out? I did some testing with my ATH-M50's and they only have 38 ohms of impedance, but I had to use the high gain setting with the pot at about 12 oclock to get a decent amount of output and the clip's volume was up fairly high. I'm using all stock component values.
I got about 800 mVrms out of it running Rockbox 3.10 at a volume setting of +3 dB (using a fullscale sine), which should be just enough to clip an O2 at high gain when running on batteries. The original firmware should be about equally loud (assuming you have the volume setting on "High", which I suspect may not be the case right now - you shouldn't have to crank the volume with the M50s running unamped). Staying a few dB shy of full output should be fine.
@dewasiuk, I reviewed the Clip+ early on in my blog with measurements. It's good for about 0.5 Vrms.
Hey all, Just received my O2 from JDSlabs today!
John from JDSlabs is very good with communication, shipping and also the product is solid. Good customer service.
Turns out, it came with the grounding wire soldered already so all I had to do was stuff it in the enclosure and screw the front panel on.
I have a few questions, concerns, feedback:
There is a lot of distortion above the 10-11 o' clock position when connected to my source. The amp itself has no distortion which is SOLID. With my headphones plugged in, the amp has ZERO distortion with the volume full. When I plug in my line out from my computer and have it readily connected, the distortion is terribly loud and get louder as I turn the volume up. It is noticeable with music playing after the 11 o clock position.
My computer/onboard sound card line out is my source and I have a 3.5mm-to-RCA connection going from my motherboard soundcard to my Denon AV receiver. From my Denon AV receiver, I have another RCA-to-3.5mm connection going from it's "Tape/MD OUT" to the Objective2 head amp's line in. This is stupid since I could just use a 3.5mm-to-3.5mm directly from my computer's line out to the headamp but I don't have one right now. Could this be the cause of the distortion? Too many cables and connections?
Using that same connection (Computer onboard to Denon AV receiver) and using speakers, there is distortion starting at +02 db which is fairly high. Using digital out, there is NO distortion even at higher levels. Volume is set to MAX on my computer.
When I am listening through this setup, I have to set the computer volume at 40%-50% or less because anything above that will cause even greater distortion. If I set it to max volume on the computer, the 9 o'clock position on the headamp will cause very noticeable and annoying distortion so I have to set it low.
Any suggestions on how to improve this?
The OPTIMAL way I was planning on setting this up was to use the digital out from my computer > Denon AV Receiver instead of the onboard soundcard's line out, because the digital optical out sounds 10X better, both speakers and headphones. The signal is PCM and unaltered so it allows the Denon's onboard DAC and signal processing to do its things. However, if I use the digital optical out, the Denon's "Tape/MD OUT" does not work. I think it says in the manual that the signals must be both analog (in AND out) for it to work. I tried the "Pre Out" fronts and same result.
The only compromise I can think of is to use the Denon's headphone out. That way I can use digital out to send clear signal to the Denon AV receiver and make use of its DAC and tone controls if needed. From there I can use a simple 1/4" to 1.8" connection to the headamp from the Denon's headphone out. Does anyone see any problems with this connection? Going through the Denon's headphone out and then again to the headphone amp... would that cause some double amping and result in some unexpected outcome?
Feedback:
I love this amp it's great and for the money sounds good. However, paired with my flat Shure SRH840 headphones, the sound is sibilant and even jarring with I hear cymbals and highs. Anyone else notice this?
Picture:
John from JDSlabs is very good with communication, shipping and also the product is solid. Good customer service.
Turns out, it came with the grounding wire soldered already so all I had to do was stuff it in the enclosure and screw the front panel on.
I have a few questions, concerns, feedback:
There is a lot of distortion above the 10-11 o' clock position when connected to my source. The amp itself has no distortion which is SOLID. With my headphones plugged in, the amp has ZERO distortion with the volume full. When I plug in my line out from my computer and have it readily connected, the distortion is terribly loud and get louder as I turn the volume up. It is noticeable with music playing after the 11 o clock position.
My computer/onboard sound card line out is my source and I have a 3.5mm-to-RCA connection going from my motherboard soundcard to my Denon AV receiver. From my Denon AV receiver, I have another RCA-to-3.5mm connection going from it's "Tape/MD OUT" to the Objective2 head amp's line in. This is stupid since I could just use a 3.5mm-to-3.5mm directly from my computer's line out to the headamp but I don't have one right now. Could this be the cause of the distortion? Too many cables and connections?
Using that same connection (Computer onboard to Denon AV receiver) and using speakers, there is distortion starting at +02 db which is fairly high. Using digital out, there is NO distortion even at higher levels. Volume is set to MAX on my computer.
When I am listening through this setup, I have to set the computer volume at 40%-50% or less because anything above that will cause even greater distortion. If I set it to max volume on the computer, the 9 o'clock position on the headamp will cause very noticeable and annoying distortion so I have to set it low.
Any suggestions on how to improve this?
The OPTIMAL way I was planning on setting this up was to use the digital out from my computer > Denon AV Receiver instead of the onboard soundcard's line out, because the digital optical out sounds 10X better, both speakers and headphones. The signal is PCM and unaltered so it allows the Denon's onboard DAC and signal processing to do its things. However, if I use the digital optical out, the Denon's "Tape/MD OUT" does not work. I think it says in the manual that the signals must be both analog (in AND out) for it to work. I tried the "Pre Out" fronts and same result.
The only compromise I can think of is to use the Denon's headphone out. That way I can use digital out to send clear signal to the Denon AV receiver and make use of its DAC and tone controls if needed. From there I can use a simple 1/4" to 1.8" connection to the headamp from the Denon's headphone out. Does anyone see any problems with this connection? Going through the Denon's headphone out and then again to the headphone amp... would that cause some double amping and result in some unexpected outcome?
Feedback:
I love this amp it's great and for the money sounds good. However, paired with my flat Shure SRH840 headphones, the sound is sibilant and even jarring with I hear cymbals and highs. Anyone else notice this?
Picture:
An externally hosted image should be here but it was not working when we last tested it.
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the computer is absolutely causing the noise. Computers are noisy, especially from the onboard sound card. I would not expect anything less than what you describe.
Using the digital output and going through your receiver's dac should improve or completely eliminate that.
I use a digital output from my computers onboard optical out into my schiit bifrost and the sound is totally silent.
you dont want to go through the receivers h/p out into the amp. someone correct me if im wrong.
the only other alternative that comes to mind is to buy another dac. I would suggesd the ODAC when it becomes available ;-)
congrads on the amp. Its a giant for sure!
Using the digital output and going through your receiver's dac should improve or completely eliminate that.
I use a digital output from my computers onboard optical out into my schiit bifrost and the sound is totally silent.
you dont want to go through the receivers h/p out into the amp. someone correct me if im wrong.
the only other alternative that comes to mind is to buy another dac. I would suggesd the ODAC when it becomes available ;-)
congrads on the amp. Its a giant for sure!