That's good up to now 
So with U2 fitted, you should see the plus 12v and minus 12v appearing on pins 8 and 4 of all the remaining empty sockets.
If that is OK then we fit U1, and we check again that the supplies on pin 8 and 4 of U1 are still correct at plus and minus 12 volts. Assuming they are, we then confirm that pins 1 and 7 of U1 are around zero volts give or take a few millivolts.
We then move on and fit U3 and we check that in the same way as U1.
So we should have -/+12 volts (that's how we write a dual supply voltage) present on pins 4 and 8 and again, just like on U1 we should have zero or very close to it on pins 1 and 7.
Finally we fit U4 and test in exactly the same way. If it passes all those tests then its basically all functional (and should work). If it doesn't then it suggests a simple signal fault somewhere along the line.
So with U2 fitted, you should see the plus 12v and minus 12v appearing on pins 8 and 4 of all the remaining empty sockets.
If that is OK then we fit U1, and we check again that the supplies on pin 8 and 4 of U1 are still correct at plus and minus 12 volts. Assuming they are, we then confirm that pins 1 and 7 of U1 are around zero volts give or take a few millivolts.
We then move on and fit U3 and we check that in the same way as U1.
So we should have -/+12 volts (that's how we write a dual supply voltage) present on pins 4 and 8 and again, just like on U1 we should have zero or very close to it on pins 1 and 7.
Finally we fit U4 and test in exactly the same way. If it passes all those tests then its basically all functional (and should work). If it doesn't then it suggests a simple signal fault somewhere along the line.
I've posted while you were replying. See how you get on and if your still having problems then its one to look at tomorrow
It certainly sounds that way. Out of curiosity, does the suspect chip read short circuit between pins 8 and 4 (measured on a low ohms range on your meter).
As a test just to get the amp working, you can substitute other types of opamp for these. An NE5532, TL072, 4558, all will work and all are common devices.
As a test just to get the amp working, you can substitute other types of opamp for these. An NE5532, TL072, 4558, all will work and all are common devices.
I have a question to the charger circuit in the o2. There is a LDO 7812 an with the Resistor of 220ohm I have 54mA charging current. But in the Description nwavguy says the charging current is proportional to the battery voltage, and maximum 54ma. How is it done in the circuit?
And how does the charging ends? Or does it load indefinitely with low current?
And how does the charging ends? Or does it load indefinitely with low current?
I haven't got the circuit in front of me but yes, it charges continually. As the battery voltage rises during charging, less voltage is dropped across the series feed resistors and so the current effectively tapers down. So 12 volts and 220 ohm allows 54ma to pass if the battery were at zero volts. Typically a discharged 9 volt pack might be at around 7 volts at charge start. That would allow (12-7)/220 which is 22ma. When fully charged it could be around 10 volts, so (12-10)/220 or 9ma flows. And it will continue at that rate.
O2 amp cross talk problem
Hey, I wonder if someone might be able to help with debugging my o2 build?
I'm building the JDS labs kit, which included all the components and PCB. Only changes I've made are to use off board parts for the power, input and output jacks. I haven't installed it in the enclosure yet.
I'm getting a cross-talk problem: with a stereo input I'm getting a stereo output (sounds ok but not great, maybe lacking bass, stereo image seems a bit wrong), but when I hard pan the input to the left I get a strong output in the left earphone (more bass) and quiet signal through the right earphone. When I pan to the right I get almost the same volume in both earphones.
I've managed to perform the in-circuit resistance checks and raw DC voltage checks as detailed on NwAvGuy's site and everything seems fine, and both switches, LED and volume pot all seem to work as expected. I've eye balled both sides of the PCB for a while and checked for any incorrect parts/orientations or solder bridges, but I have not found any mistakes yet.
Any ideas what might be wrong? Which parts should I be concentrating on? Any help would be greatly appreciated!
Thanks,
Adam
Hey, I wonder if someone might be able to help with debugging my o2 build?
I'm building the JDS labs kit, which included all the components and PCB. Only changes I've made are to use off board parts for the power, input and output jacks. I haven't installed it in the enclosure yet.
I'm getting a cross-talk problem: with a stereo input I'm getting a stereo output (sounds ok but not great, maybe lacking bass, stereo image seems a bit wrong), but when I hard pan the input to the left I get a strong output in the left earphone (more bass) and quiet signal through the right earphone. When I pan to the right I get almost the same volume in both earphones.
I've managed to perform the in-circuit resistance checks and raw DC voltage checks as detailed on NwAvGuy's site and everything seems fine, and both switches, LED and volume pot all seem to work as expected. I've eye balled both sides of the PCB for a while and checked for any incorrect parts/orientations or solder bridges, but I have not found any mistakes yet.
Any ideas what might be wrong? Which parts should I be concentrating on? Any help would be greatly appreciated!
Thanks,
Adam
Couple of o2 questions
Hi,
I'm new to the world of DIY audio and recently built myself an o2 amp, which I'm really enjoying so far. Thanks to NwAvGuy and the community for supporting my build.
I had a couple of questions (sorry if they are obvious or inexperienced).
I'm getting feedback when the ac adapter is plugged in and the batteries are charging. I understand it's because the aluminum case needs connected to ground. I wanted to laser cut a new case out of plastic - what effect would plastic have? Obviously it wouldn't need earthed but is the case causing feedback or does earthing the case reduce feedback (I assume it's the latter)?
I also wanted to add some toggle switches - does anyone know of a component number that would suit the o2?
Thanks
Hi,
I'm new to the world of DIY audio and recently built myself an o2 amp, which I'm really enjoying so far. Thanks to NwAvGuy and the community for supporting my build.
I had a couple of questions (sorry if they are obvious or inexperienced).
I'm getting feedback when the ac adapter is plugged in and the batteries are charging. I understand it's because the aluminum case needs connected to ground. I wanted to laser cut a new case out of plastic - what effect would plastic have? Obviously it wouldn't need earthed but is the case causing feedback or does earthing the case reduce feedback (I assume it's the latter)?
I also wanted to add some toggle switches - does anyone know of a component number that would suit the o2?
Thanks
The O2 built on the official board should work in any type of case. Its self contained and all grounding and so on is taken care of via the PCB layout.
If something odd is happening when using AC and charging the batteries (is it actually OK with the batteries removed and running off AC ?) then I would be looking at the first stages of the power supply around the regulators. Have you measured the voltages to confirm the -/+12 volts is correct ?
If something odd is happening when using AC and charging the batteries (is it actually OK with the batteries removed and running off AC ?) then I would be looking at the first stages of the power supply around the regulators. Have you measured the voltages to confirm the -/+12 volts is correct ?
Thanks for your reply.
Well - I think either I'm not able to use a volt meter or something is horribly wrong. It works fine with either AC or battery alone but not together.
First thing that seems strange to me initially:
on u5
vin -------
vout------ is connected to ground when continuity tested
adj------- is not connected to ground
on u6
vin -------
vout------ is not connected to ground
adj------- is connected to ground
and voltages
u5
vin ------- 25v
vout------ 0v
adj------- 48.8v
u6
vin -------0v
vout------ 0v
adj------- 0v
Well - I think either I'm not able to use a volt meter or something is horribly wrong. It works fine with either AC or battery alone but not together.
First thing that seems strange to me initially:
on u5
vin -------
vout------ is connected to ground when continuity tested
adj------- is not connected to ground
on u6
vin -------
vout------ is not connected to ground
adj------- is connected to ground
and voltages
u5
vin ------- 25v
vout------ 0v
adj------- 48.8v
u6
vin -------0v
vout------ 0v
adj------- 0v
Last edited:
Ok I've obviously had my voltmeter set wrong I thought wavy line for AC as the adapter was AC.
yes I'm getting 12 and -12v both with ac and batteries and with ac alone.
with batteries I'm getting 0v I must have let them run dry is it perhaps when the batteries are drained I get the hum I'll have to test that.
yes I'm getting 12 and -12v both with ac and batteries and with ac alone.
with batteries I'm getting 0v I must have let them run dry is it perhaps when the batteries are drained I get the hum I'll have to test that.
The output from the regulators should be constant whether charging flat batteries or not.
Post #3775 here gives detailed measurements. You should get these voltages when charging the batteries and having the O2 playing. Just do the measurements, no need to pull the opamps out.
http://www.diyaudio.com/forums/head...o2-headphone-amp-diy-project.html#post3806667
Post #3775 here gives detailed measurements. You should get these voltages when charging the batteries and having the O2 playing. Just do the measurements, no need to pull the opamps out.
http://www.diyaudio.com/forums/head...o2-headphone-amp-diy-project.html#post3806667
Hello,
I'm curious if anyone tried NJM2114 instead of NJM4556 in buffer role. NJM2114 offers much better specs, especially in terms of noise, bandwidth and THD still offering high output current. JRC datasheets are very poor in details. I'm not sure if it would be stable without additional compensation in unity buffer configuration. Any thoughts?
Regards,
Miłosz
I'm curious if anyone tried NJM2114 instead of NJM4556 in buffer role. NJM2114 offers much better specs, especially in terms of noise, bandwidth and THD still offering high output current. JRC datasheets are very poor in details. I'm not sure if it would be stable without additional compensation in unity buffer configuration. Any thoughts?
Regards,
Miłosz