The Objective2 (O2) Headphone Amp DIY Project

[astramor]

Hi to everyone,

I just finished soldering and started with testing.
I connected + BT1 and - BT with my DMM I get 22,5 V and it drops to 18 V switching the O2 on.
Nothing is getting hot, the LED is working. With an installed U2 the drop is even higher. Then the voltage drops to 10,5 V.

Can somebody give me a hint to find the error? I'm still in my beginnings with diy audio, this is my third project and I am not sure, where to search for the error.

Is it the power supply and U5 and U6 or can it be a damage of Q1 or Q2?

[RocketScientist]

IMPORTANT: The self tapping Box Enclosure case screws can sometimes produce large enough aluminum "shavings" to cause short circuits and potentially serious problems. This may account for the few "spontaneous O2 deaths" that have been reported.

I know the screw problem has been mentioned previously, but I've added two notes to the O2 Details article and wanted to add another note here. I would encourage everyone to install all 8 screws fully into an empty enclosure first, remove the screws, blow out any bits of aluminum, and then assemble the amp.

[Atilla]

Originally Posted by RocketScientist

IMPORTANT:
I know the screw problem has been mentioned previously, but I've added two notes to the O2 Details article and wanted to add another note here. I would encourage everyone to install all 8 screws fully into an empty enclosure first, remove the screws, blow out any bits of aluminum, and then assemble the amp.

This is really important. I never drill, tap or screw anything on a filled case. Always do that first and blow/wash the shavings off first. Metal shavings somehow always find their way to where they shouldn't be.

[BuildMeSomething]

Finally finshed the case for my O2... hope you like





Regards

Paul

[Twinster]

Very nice looking case Paul.

Are you a Toronto Maple Leaf hockey fan by any chance? ;^P

[BuildMeSomething]

lol... It was more of a car based influence than that of TML

[merlin2069er]

Very nice. Is that a plastic or metal shell?

[BuildMeSomething]

It's plastic, I used layered Styrine sheeting to build the full case. The curved edges are done by wrapping & glueing a 0.5mm thick sheet around the inner box structure.

I was going to do a 'How To' but forgot to take a few key pictures during the build.

[raspunsen]

Well, i'm facing a little problem with my O2, and i hope you guys can help me sort it out.
The thing is, when i finished assembling my O2 i only had batteries to test it out. Everything seems fine, and the amp seems to work flawlessly.
Now i got myself an universal AC/AC adapter, with adjustable voltage and 2000mA max.
I set it to 16 volts, removed the cheap non rechargeable batteries and tryed to power the amp. The LED comes on, but it does not output any sound. Still works fine with batteries only.
Tried 18 volt, 20 volt and even 24 volt and the result is the same.
Am i just missing something here? Is it normal for it to work ok with batteries but not with wall adapter?
Thanks in advance.

[agdr]

Originally Posted by raspunsen

The LED comes on, but it does not output any sound. Still works fine with batteries only.

With the batteries removed and O2 power switch off, connect your power adapter and measure the DC voltage from ground (metal shell of the gain switch) to the two outermost battery terminals (closest to board edge and the one farthest from the board edge) and see what you get. Should be around +12V and -12V.

I would take a guess that your power adapter might be mislabeled and may actually be a DC adaptor rather than AC. That would make only one of the two power rails work. Do you have a link to a product page or data sheet for that power adaptor?