The Objective2 (O2) Headphone Amp DIY Project

[6L6]

I just got my stainless steel faceplate from member 'Yangoran' , it looks fantastic!


I need a different knob, that one is a bit too big.

[lenconian]

OK, I've completed the O2 with the new caps.
Now I've started to measure and things don't quite add up.
U2 is installed, and all the measurements are fine except for P2.
I've included a picture to make things clearer;



On both points at P2 I get ~1.4V instead of the 0-0.008V I should be getting.
Any input on troubleshooting would be greatly appreciated.

Thank you very much.

[hallom]

hey guys, anyone here using e-mu 0404 usb? i have one and i want to change it, and i was wondering how odac+o2 compares to it when using as a dac+preamp?

[tecnogadget]

Hello! I already got the Objetive O2 PBC from JDS labs. Now im buying all the components.
Are the Op Amps NJM4556AD and NJM4556A the same thing? Because my suplier only has the latter (NJM4556A) so im not shure if they are the right ones.

I also got problems getting the High Eficiency LED , how should i ask for it at the store?
Is it 0.5mA or just a simply 10mA led? That part got me confused on NwAvGuy post.

[tecnogadget]

So , if i cant get the NJM4556AD op amp , can i just use in U1-U3-U4 (Nwavguy PBC) the NJM2068D ? Would i loose some performance?
Thanks

[nezbleu]

Originally Posted by lenconian

U2 is installed, and all the measurements are fine except for P2.

On both points at P2 I get ~1.4V instead of the 0-0.008V I should be getting.
Any input on troubleshooting would be greatly appreciated.

With just U2 installed, the outputs at P2 are floating, they aren't connected to anything. There is nothing to measure there until the op-amps are installed.

[nezbleu]

Originally Posted by tecnogadget

Are the Op Amps NJM4556AD and NJM4556A the same thing? Because my suplier only has the latter (NJM4556A) so im not shure if they are the right ones.

I also got problems getting the High Eficiency LED , how should i ask for it at the store?
Is it 0.5mA or just a simply 10mA led? That part got me confused on NwAvGuy post.

Did you check any datasheets to see what the difference is between the 4556A and the 4556AD? The "D" refers to the package, in this case DIP8. The other available packages are DMP8 (NJM4556AM), SIP8 (NJM4556AL) and SSOP8 (NJM4556AV). All of them are NJM4556A, as long as you get one in DIP8 package you have the right one.

As for the LED, read NWAVGuy's blog again, the LED has to operate on about 0.5mA, and it has to have the right forward voltage drop. Look up the part on Mouser's site, get the data sheet or specs, and show it to your supplier.

[nezbleu]

Originally Posted by tecnogadget

So , if i cant get the NJM4556AD op amp , can i just use in U1-U3-U4 (Nwavguy PBC) the NJM2068D ? Would i loose some performance?
Thanks

You would lose a lot of performance. The 2068 cannot provide nearly as much current as the correct op-amps.

[lenconian]

Originally Posted by nezbleu

With just U2 installed, the outputs at P2 are floating, they aren't connected to anything. There is nothing to measure there until the op-amps are installed.

Thank you very much nezbleu, so you think I can just go on in the measurement process with the OP-amps installed?
I wasn't sure and did not want to destroy the OP-amps...

[lenconian]

All right, thanks to you guys, the amp is up and running!
I'm glad there was no soldering mistake, everything worked right from the start

So here it is;



The next step will be building a case, I'll keep you posted.