I would need to rig a custom cable to measure the actual current but the specs are showing >80ma.
The new USB controller allows me to 'lie' to the host by reporting 'self powered' and '0ma' current load. The ODAC-revB will now work with my iPad Mini using the Camera Connection Kit. The dac will also work the new Nexus 9 running 5.1.1 Lollipop with the proper cable. Unfortunately my 2012 Nexus 7 with 5.1.1 does not recognize the DAC.
George
The new USB controller allows me to 'lie' to the host by reporting 'self powered' and '0ma' current load. The ODAC-revB will now work with my iPad Mini using the Camera Connection Kit. The dac will also work the new Nexus 9 running 5.1.1 Lollipop with the proper cable. Unfortunately my 2012 Nexus 7 with 5.1.1 does not recognize the DAC.
George
80mA is fine - anything below that 100mA basic current level for USB 2.0 is great. From what I hear most USB 2.0 bus implementations these days are good for the full 500mA without making a request from the host controller, but I don't trust it. 
That's a neat tricking being able to tell the host it is a 0mA device!
That's a neat tricking being able to tell the host it is a 0mA device!
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The whole thing is quite a soap opera! NwAvGuy made the O2 headamp first in the fall of 2011. He followed that with the ODAC DAC in the spring of 2012, which he made in collaboration with George here. Then NwAvGuy dissappeared in the fall of 2012.
The ODAC fits in the O2 where the batteries would otherwise go and is self-powered from the PC USB bus. George has just released a revision of the ODAC.
If a USB isolator is used in conjunction with the ODAC (or any USB DAC, for that matter), does Windows still recognize the ODAC as being the connected device, or does the USB isolator become the connected device?
https://www.circuitsathome.com/products-page/usb-interfaces
If the latter, wouldn't it affect the functionality of the ODAC as a Windows sound device?
https://www.circuitsathome.com/products-page/usb-interfaces
If the latter, wouldn't it affect the functionality of the ODAC as a Windows sound device?
I have used galvanic isolators with the ODAC and other UAC1 devices with no noticable problems.
-- Be aware that the isolator on board power supply can be a source of noise if not properly designed.
-- The current crop of galvanic isolators will only work with UAC1 and not the high speed UAC2 audio. Properly designed UAC2 devices should handle the isolator interface but will not support anthing beyond 96k sample rates.
regards
Having some problems with my O2 kit
Hi. I don't know it this is the correct place to post it, but I have some problems with my O2 I don't know how to solve. First I have finished soldering all the components a few days ago. I did all the measurements in the nwavguy blog and they are correct. The problem is that I can hear an oscillation accelerating in the left channel. I tried swapping u3 and u4, but the oscillation is still in the left channel. Do you know what could it be causing it? Thanks kysho
Hi. I don't know it this is the correct place to post it, but I have some problems with my O2 I don't know how to solve. First I have finished soldering all the components a few days ago. I did all the measurements in the nwavguy blog and they are correct. The problem is that I can hear an oscillation accelerating in the left channel. I tried swapping u3 and u4, but the oscillation is still in the left channel. Do you know what could it be causing it? Thanks kysho
Is the amplitude of the oscillation affected by the volume control setting ? If 'no' then the problem is in the final stages or the power supply.
If 'yes' then does altering the gain switch alter anything about the noise such as amplitude or frequency ?
Does switching to battery power make any difference ?
Does disconnecting the inputs make any difference ?
If 'yes' then does altering the gain switch alter anything about the noise such as amplitude or frequency ?
Does switching to battery power make any difference ?
Does disconnecting the inputs make any difference ?
That sounds a bit strange. What is the AC adapter you are using ? It needs to be an AC output type and delivering at least 12 volts AC under load.
This is a copy and paste from my post (#3775) on testing and checking the O2. Does it pass all these tests ?
Measurement.
1) With your meter set to DC volts and with the BLACK meter lead firmly connected to ground (that is the common junction of C2, C3, C4 and C5 etc) measure the voltage on the striped end of D3. It should be higher than PLUS 15 volts and lower than PLUS 28 volts.
2) Keeping the BLACK lead on ground measure the DC voltage on the NON striped end of D4. It should be higher than MINUS 15 volts and lower than MINUS 28 volts.
If those conditions are OK now check the output of the two regulators. If the readings are incorrect you have a problem with either the AC input, a problem with the two rectifier diodes or a problem with incorrect or faulty regulators causing a short or partial short. Make sure that a 7812 is fitted for U5 and a 7912 for U6. Also make sure any electroylitics are fitted correctly with respect to polarity.
Checking the output of the regulators.
The BLACK meter lead is kept on ground unless otherwise stated.
1) Measure the DC voltage on the striped end of D1. It should be 11.5 to 12 volts approximately.
2) Measure the DC voltage on the NON striped end of D5. It should be MINUS 11.5to 12 volts DC approximately.
If you have incorrect readings for the plus and minus 12 volts yet have correct input voltages to the regulators, then the problem can only be either the regulators themselves or incorrectly fitted D1 and D5.
This is a copy and paste from my post (#3775) on testing and checking the O2. Does it pass all these tests ?
Measurement.
1) With your meter set to DC volts and with the BLACK meter lead firmly connected to ground (that is the common junction of C2, C3, C4 and C5 etc) measure the voltage on the striped end of D3. It should be higher than PLUS 15 volts and lower than PLUS 28 volts.
2) Keeping the BLACK lead on ground measure the DC voltage on the NON striped end of D4. It should be higher than MINUS 15 volts and lower than MINUS 28 volts.
If those conditions are OK now check the output of the two regulators. If the readings are incorrect you have a problem with either the AC input, a problem with the two rectifier diodes or a problem with incorrect or faulty regulators causing a short or partial short. Make sure that a 7812 is fitted for U5 and a 7912 for U6. Also make sure any electroylitics are fitted correctly with respect to polarity.
Checking the output of the regulators.
The BLACK meter lead is kept on ground unless otherwise stated.
1) Measure the DC voltage on the striped end of D1. It should be 11.5 to 12 volts approximately.
2) Measure the DC voltage on the NON striped end of D5. It should be MINUS 11.5to 12 volts DC approximately.
If you have incorrect readings for the plus and minus 12 volts yet have correct input voltages to the regulators, then the problem can only be either the regulators themselves or incorrectly fitted D1 and D5.
Thanks for the help.
I forget to mention, but the oscillation start after a few seconds (15 or so) . If I turn of and on immediately the oscillation appear earlier. Could it be a capacitor?
I did the test from o2%2520voltages%2520all%2520ICs%255B3%255D.png (image)
and they were ok. I will do the test you said when I have some spare time.
Regards
Kysho
I forget to mention, but the oscillation start after a few seconds (15 or so) . If I turn of and on immediately the oscillation appear earlier. Could it be a capacitor?
I did the test from o2%2520voltages%2520all%2520ICs%255B3%255D.png (image)
and they were ok. I will do the test you said when I have some spare time.
Regards
Kysho
Its hard to say without more detailed tests. An oscilloscope would find this in seconds.
Do the checks I listed and be sure. Also make sure the voltage regs are running cool.
It could be a capacitor (but unlikely). It could also be a problem with the FET switches and the comparator. You can safely link the FET's out as a test which would be the next step if you don't find anything definite as faulty.
Check it all one step at a time.
Do the checks I listed and be sure. Also make sure the voltage regs are running cool.
It could be a capacitor (but unlikely). It could also be a problem with the FET switches and the comparator. You can safely link the FET's out as a test which would be the next step if you don't find anything definite as faulty.
Check it all one step at a time.
Use the scope to look at power rails on pin 4 and 8 of the opamps. Should be absolutely clean (scope set to AC volts and high sensitivity such as 5mv/dv). If that is OK then you need to use the scope to look at the opamp outputs and see where in the chain the noise is beginning.
I think the problem could well be in the FET switch/comparator area or the regulators.
I think the problem could well be in the FET switch/comparator area or the regulators.
Negative.
LME4990 for input gain stage, due to it`s exellent THD, PSRR, CMRR, drive 600 Ohm, could to be purchased directly from TI at very good price + reasonable shipping.
NJM4556 has more output current than OPA2209. Pay attention: NJM4556 RATED for Io=70mA, OPA2209 Short circuit current Isc=65mA.
Even with more noisy NJM4556 whole O2 still -130dB noise floor. There is quite few even $1000+ amps that can to reach that level. THD - same as noise. But if you want true better specs, than LME49600 or BUF634 are reasonable to be considered.
In addition, look at adgr audio website, there is several good tweaks of O2 discribed.
Nwavguys's opamp analysis and choices still remains valid to this day.
For the vanilla version of the O2, while the njm2068, all things considered, probably still is the best choice, you could try alternatives. But for the output buffer, there is hardly any competitor to the njm4556, in terms of output current capability.
Agdr's booster board is one, but it uses the lme49600 wrapped around another opamp.