If swapping the opamps swaps the fault (or part of the fault) over then yes, its pretty conclusive there is a problem with one.
You can fit any common types as a quick test such as 5532's or 4558's etc. You won't get the full drive ability of the original 4556 but it will show if the problem is fixed.
Very odd to get a faulty opamp though... but swapping them over is conclusive enough.
I preparing to build my own O2 amp in the next week or so, but I have a couple questions as well as a few things I'd like to clarify.
I'm gong with rear RCA input, do I need to be concerned at all about the jack grounding on the chassis? Only reason I ask is that the JDS Labs guide says that paper washers should be used if placing RCA rear inputs. I assume this is due to grounding concerns.
Am I reading the schematic correctly that R1, R2, D2, and D6 as well as the battery terminals can be omitted since I am only going to run this on AC and never on batteries.
Finally a "can this work". Ultimately, I would like to purchase an ODAC as well down the road and connect it to the O2 within the same enclosure. When I do this I would like to use the RCAs as line out on the ODAC to go to my speakers and the line out on the O2 to power my headphones. Can I make it so that the unit would automatically switch based on the power state of the O2? Maybe a relay triggered by powering on the O2 between the line out on the ODAC and the RCAs and 1/4" phone jack.
Thanks for any help you can give.
I'm gong with rear RCA input, do I need to be concerned at all about the jack grounding on the chassis? Only reason I ask is that the JDS Labs guide says that paper washers should be used if placing RCA rear inputs. I assume this is due to grounding concerns.
Am I reading the schematic correctly that R1, R2, D2, and D6 as well as the battery terminals can be omitted since I am only going to run this on AC and never on batteries.
Finally a "can this work". Ultimately, I would like to purchase an ODAC as well down the road and connect it to the O2 within the same enclosure. When I do this I would like to use the RCAs as line out on the ODAC to go to my speakers and the line out on the O2 to power my headphones. Can I make it so that the unit would automatically switch based on the power state of the O2? Maybe a relay triggered by powering on the O2 between the line out on the ODAC and the RCAs and 1/4" phone jack.
Thanks for any help you can give.
I have to assume that JDS recommends the insulating washers so that there can be a single point ground elsewhere for the enclosure.
Yes, those are the parts you can omit for AC-only use.
You could modify your unit with a relay to switch outputs. I can't say exactly how because I am uncertain of your final configuration.
Yes, those are the parts you can omit for AC-only use.
You could modify your unit with a relay to switch outputs. I can't say exactly how because I am uncertain of your final configuration.
I'm going to remote mount AC power on the rear, remote mount the inputs as RCAs on the rear and remote mount the headphone output as a 1/4" jack up front. All three will have wires that could easily route through a relay.
Sounds more like a job for something like The Wire (headphone amp), BAL-SE version.
A DAC may be quite hard-pressed to provide anything like the dynamic range of a volume pot, btw. Total output dynamic range of an O2 (maximum signal to minimum noise level over the entire volume control range with mains supply) is about 130-133 dB according to measurements, expected theoretical value would be about 136-138 dB. It takes a truly first-rate DAC to even get close.
Of course you can often get away with 2 Vrms of output and 5 µV of noise (@20 kHz BW) in practice, which is a more manageable 112 dB, but still. Owners of the Asus Xonar ST(X) cards and somewhat sensitive in-ears have been surprised by audible noise when switching to 44.1 kHz because dynamic range of the card at this sample rate degrades to about 108 dB "only" - the headphone output is quite hot at 7 Vrms, so that's about 25 µV worth of noise.
A DAC may be quite hard-pressed to provide anything like the dynamic range of a volume pot, btw. Total output dynamic range of an O2 (maximum signal to minimum noise level over the entire volume control range with mains supply) is about 130-133 dB according to measurements, expected theoretical value would be about 136-138 dB. It takes a truly first-rate DAC to even get close.
Of course you can often get away with 2 Vrms of output and 5 µV of noise (@20 kHz BW) in practice, which is a more manageable 112 dB, but still. Owners of the Asus Xonar ST(X) cards and somewhat sensitive in-ears have been surprised by audible noise when switching to 44.1 kHz because dynamic range of the card at this sample rate degrades to about 108 dB "only" - the headphone output is quite hot at 7 Vrms, so that's about 25 µV worth of noise.
Hi, I built my O2 a couple years ago, and it 'works' and have been using it happily for a long time.
But there had always been slight issues with my build that I was never able to fix. That troubled me and I revisited it recently, but after abusing the PCB to the point that many pads and traces were burnt, I still wasn't able to fix it.
The issue is that the regulated DC rails should be +/-12V at D1/D5, but my build measures +11.9V and -15.1V with 16.9VAC 1200mA input. With 13VAC input, it is more closer (within spec?) at +11.9V and -12.3V. Unregulated power at D3/D4 is in spec though (+/-23.1V@17VAC; +/-17.2V@13VAC).
I wonder what are the consequences running the amp at its unbalanced state at +12V and -15V, seeing that it never caught fire nor burnt my phones, and nonetheless, how could I fix this issue? I tried replacing the 7812/7912 regulators and checked them for bridges, but no dice.
But there had always been slight issues with my build that I was never able to fix. That troubled me and I revisited it recently, but after abusing the PCB to the point that many pads and traces were burnt, I still wasn't able to fix it.
The issue is that the regulated DC rails should be +/-12V at D1/D5, but my build measures +11.9V and -15.1V with 16.9VAC 1200mA input. With 13VAC input, it is more closer (within spec?) at +11.9V and -12.3V. Unregulated power at D3/D4 is in spec though (+/-23.1V@17VAC; +/-17.2V@13VAC).
I wonder what are the consequences running the amp at its unbalanced state at +12V and -15V, seeing that it never caught fire nor burnt my phones, and nonetheless, how could I fix this issue? I tried replacing the 7812/7912 regulators and checked them for bridges, but no dice.
I haven't got the O2 diagram in front of me but the problem has to be around the negative regulator. The reason the output is nearer -12 volts with a lower input is simply because the unregulated rail has fallen.
Check very carefully the fitting of the reg and the continuity of the reg ground pin to the main ground. If that was floating it would cause this.
No consequencies from running unbalanced apart from the fact that rail will be noisy and have ripple on it.
Check very carefully the fitting of the reg and the continuity of the reg ground pin to the main ground. If that was floating it would cause this.
No consequencies from running unbalanced apart from the fact that rail will be noisy and have ripple on it.
Wow thanks! You were right about it being a floating ground, wasn't the fitting though. I reckon the grounding on the regulator was faulty, I had a direct jumper to the pin all the time and it didn't work.
Did the whole thing again and got a healthy voltage! Strange though that my original replacement 7912 didn't work, I guess the third time's a charm (or I just resoldered my old regulator over and over again)
Thank you for fixing my 4-year-old bug!
Did the whole thing again and got a healthy voltage! Strange though that my original replacement 7912 didn't work, I guess the third time's a charm (or I just resoldered my old regulator over and over again)
Thank you for fixing my 4-year-old bug!
help with some troubleshooting
I am having some issues with an O2 I built 2 years ago. I tried searching the thread, but the words "tap" and "click" are kind of generic
Everything usually works fine at first, but eventually a rather load humming-click (with an increasing click speed) shows up.
How do I correct this? If I tap the top of the amp or lift and tap the whole thing on my desk, it goes away.
The problem has gotten worse in the last few months. It used to occur a few times a day, now it is every few minutes.
I feel like I should know what component is affected by mechanical tapping like this, but I can't put my finger on it.
Any help would be appreciated!
I am having some issues with an O2 I built 2 years ago. I tried searching the thread, but the words "tap" and "click" are kind of generic
Everything usually works fine at first, but eventually a rather load humming-click (with an increasing click speed) shows up.
How do I correct this? If I tap the top of the amp or lift and tap the whole thing on my desk, it goes away.
The problem has gotten worse in the last few months. It used to occur a few times a day, now it is every few minutes.
I feel like I should know what component is affected by mechanical tapping like this, but I can't put my finger on it.
Any help would be appreciated!
This sounds like a "low battery condition". Check out Nwavguy's blog post from March 11, 2012 in his blog here: NwAvGuy: O2 Headphone Amp (search for "low bat") and the troubleshooting page here: NwAvGuy: O2 Details (under "clicking or rapid turn on/off")
I always mount RCA jacks on insulating washers, it's the safest way if you are concerned about case grounding. And usually, Cases should be at a power ground potential for safety purposes, which you want to separate from signal ground to reduce noise. Most decent RCA jacks come with insulating washers with a "shoulder" on them and you drill a larger hold to accommodate the shoulder to keep the socket centered in the hole and insulated from the chassis.
If you are interested my blog post: http://www.diyaudio.com/forums/blog...2-b3-080-desktop-case-rcas-1-4-inch-jack.html details how I wired O2's for RCA's 1/4 and volume control (with the board facing the rear..)
You can! Something like an Antek AN-0112:
AN-0112 - 10VA 12V Transformer - AnTek Products Corp
You can either use a bigger case or box the transformer up separately, similar to what I did here in post #829:
http://www.diyaudio.com/forums/head...ersion-o2-desktop-amp-oda-17.html#post4400957
Did you faced the same problem on AC power?
Are the rechargeable batteries useful lifespan is over?
If IC sockets were used - try resitting them by gently pushing all DIP 8 ICs downwards.
If the above steps fail, you may have to chk for dry solders
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