I have a desktop O2+ODAC combo, ODAC output duplicated to RCAs, J2 grounded to the enclosure, everything works fine. Last days I use only ODAC with unpowered O2, connected to another amp with RCAs. And suddenly I noticed a little hum, it disappears when I touch the enclosure. I read somewhere that one RCA also should be grounded to the enclosure. But not sure if it is proper to make two groundings. Could you help me with it?
Just try it by grounding one RCA to the case. You can also try grounding it via a low value resistor like a 10 ohm.
You could also try grounding (or grounding via a 10 ohm) just the zero volt line of the power supply to the case.
Although the case doesn't have to be grounded or tied to the circuit it is normal practice to make it so and not just leave it floating.
You could also try grounding (or grounding via a 10 ohm) just the zero volt line of the power supply to the case.
Although the case doesn't have to be grounded or tied to the circuit it is normal practice to make it so and not just leave it floating.
Hello,
May I ask a very newbie question? I have made a search but surprisingly couldn't find anyone asking..... Is it possible to feed the O2 with a 19VDC battery pack? Of course not through the AC adaptor socket but directly to the batteries terminals (I am assuming they are in line feeding 18v to the Amp...)
The reasons I ask are the following: I like a lot the idea of this Amp, but these 9volt bricks are not my cup of tea.... Instead i would use the space to place a pi zero + miniboss dac and have a small cute streamer (the pi must be a few mm larger but i will figure that out). All powered by one of these power banks with 5v and 19v DC out. But before moving forward, i would like to know if the thing is going to explode when i attempt such a genius idea.
What do you guys think?
May I ask a very newbie question? I have made a search but surprisingly couldn't find anyone asking..... Is it possible to feed the O2 with a 19VDC battery pack? Of course not through the AC adaptor socket but directly to the batteries terminals (I am assuming they are in line feeding 18v to the Amp...)
The reasons I ask are the following: I like a lot the idea of this Amp, but these 9volt bricks are not my cup of tea.... Instead i would use the space to place a pi zero + miniboss dac and have a small cute streamer (the pi must be a few mm larger but i will figure that out). All powered by one of these power banks with 5v and 19v DC out. But before moving forward, i would like to know if the thing is going to explode when i attempt such a genius idea.
What do you guys think?
The O2 power supply is +9v, ground, and -9v. That is 18 volts in total, but it ignores the proper reference.
So you'd need to somehow split your 19 volts, adding a midpoint ground.
So you'd need to somehow split your 19 volts, adding a midpoint ground.
Thanks Sofaspud,
That goes well beyond what my knowledge allows me to do and I don't think I find a power bank with 1x5 + 2x9V outputs... 🙁
That goes well beyond what my knowledge allows me to do and I don't think I find a power bank with 1x5 + 2x9V outputs... 🙁
Two caps and two resistors, one of each in parallel and then those pairs in series. The middle becomes the ground point.
Or, there are IC's that create a negative voltage from a positive voltage.
They do affect the performance of the power supply to one degree or another of course.
Two lithiums in series give a nominal 7.4 volts. Maybe a pair for + and a pair for - would work for you.
Or, there are IC's that create a negative voltage from a positive voltage.
They do affect the performance of the power supply to one degree or another of course.
Two lithiums in series give a nominal 7.4 volts. Maybe a pair for + and a pair for - would work for you.
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Hmmm...I think O2 can be powered via a non-differential PSU, let's analyse the schematic. GND will still be used for audio circuitry only. Not sure how the power management will work, but I might give it a try in the next few days and see how it goes when powered via 16...18V supply.
Virtual Ground Circuits might be a good starting point. You can also use a digital multimeter to measure the voltage properly.
Thanks for the link and for sharing your observations from using the 18v supply when you do it 🙂
Hey everyone, been looking at all of the documentation and this looks like a great project, but I have a question that seems simple and must have been asked but my search skills are not up to finding an answer on this thread. So apologies if this is tedious, but...
NwAvGuy makes a lot in the documentation of avoiding placing the input jack too near to the power management circuity. Does this include the batteries themselves? I would ideally like to build an O2 with both AC input and a 6.35mm stereo input socket on a rear panel, but I want keep the batteries in order to retain the O2's portability. Will placing the input socket over the batteries risk introducing noise into the circuit? I am aware that I will need to build a taller enclosure to accommodate this, but that is not a problem.
Speaking of the home-made enclosure, NwAvGuy's documentation seems to say that an enclosure with no metal (I'm thinking all-wood) should have a separate metal plate wired to the input ground and housed underneath the PCB. Am I reading this right?
Thanks in advance 🙂
NwAvGuy makes a lot in the documentation of avoiding placing the input jack too near to the power management circuity. Does this include the batteries themselves? I would ideally like to build an O2 with both AC input and a 6.35mm stereo input socket on a rear panel, but I want keep the batteries in order to retain the O2's portability. Will placing the input socket over the batteries risk introducing noise into the circuit? I am aware that I will need to build a taller enclosure to accommodate this, but that is not a problem.
Speaking of the home-made enclosure, NwAvGuy's documentation seems to say that an enclosure with no metal (I'm thinking all-wood) should have a separate metal plate wired to the input ground and housed underneath the PCB. Am I reading this right?
Thanks in advance 🙂
I have placed large stepped volume control mounted on the rear side of the metal case behind those regulators with shielded wires salvaged from old PC CDROM drive running over whole pcb due to space constraints. No audible noises even at highest gain settings of 8X.
teljim88,
In the spirit of DIY, I'd say try mounting the input over the batteries where you want it and see what you think.
Since you're planning to make an enclosure of wood, you can mock one up from cardboard and duct tape and not worry about changes when you switch to the real case.
Move the input around in the cardboard mockup all you want. When you like it, make it out of wood and enjoy knowing that you tried different things and picked the best for you.
Enjoy the process!
Ryan
In the spirit of DIY, I'd say try mounting the input over the batteries where you want it and see what you think.
Since you're planning to make an enclosure of wood, you can mock one up from cardboard and duct tape and not worry about changes when you switch to the real case.
Move the input around in the cardboard mockup all you want. When you like it, make it out of wood and enjoy knowing that you tried different things and picked the best for you.
Enjoy the process!
Ryan
I've built my desktop O2 combo with RCA output like pictured. I want to use ODAC source with O2 (empty RCAs) or with external amp (empty power). However in the second case I hear some high frequency noise especially when music start/stop on PC. The pcb is grounded to the case. What's the problem?
https://cdn.head-fi.org/a/8818537.jpg
https://cdn.head-fi.org/a/8818537.jpg
I've no experience of the ODAC I'm afraid but hopefully someone might have some ideas. I would guess you need to look with a decent scope to try and pick up where the noise is entering the chain.
Use shielded wires and connect shield to GND and signal wire to RCA L/R.
I've added RCA plugs to my O2 and short shielded wires and there's zero noise or interferences.
I've added RCA plugs to my O2 and short shielded wires and there's zero noise or interferences.
I think the interference is from USB digital signal. Is your O2 has a DAC inside?