[qusp]

Quote:

I'm pretty damn sure it is not an approval...

yes, i suppose we can rule that out, but that does still leave a lot of combinations

 

[BobSaysHi]

My O2 cost me $32. For $32 it's damn good.
 
My second O2 is not working though, and I'm not sure where to go for help.

 

[shadow419]

If you went through the checklist of power measurements and everything comes up fine but you get no sound, I'd go to the source.

 

[BobSaysHi]

I went ahead and posted on diyaudio with my problem, but because I only have a handful of posts over there, I need moderator approval. Great.
 
 

 

[wakibaki]

Quote:

My second O2 is not working though, and I'm not sure where to go for help.

OK, you have one working, this is a big help.
 
Is the amp completely dead or is there a problem with the sound on one or both channels? It helps to know.
 
The O2 is not really a complex assembly, you should be able to get it working pretty much by inspection.
 
First check that you really have built the amplifiers identically. It's surprising what can slip past you when you're consumed by enthusiasm.
 
You really need a multimeter. It makes checking things much easier, but you don't need to spend a lot of money. An accurate meter is a nice thing to have but mostly what you need is an indication of resistance and AC and DC voltage and current. A continuity setting with an audible indication means you don't have to look away from the probes when checking that things are connected.
 
Work through all the components, checking that each pin is connected to the correct pins on other components. You can look at the posted schematic (on google docs) to see what's what. Try to make the tests by putting the probes on the component pins, this way you're testing the solder joints. The meter uses a low voltage for these tests and will not damage the components.
 
If you can't find any problems this way, check the power supply rails. Find a point that is connected to ground and check for an indication of the correct supply voltages between ground and the power pins on the opamps. If you don't find satisfactory readings this will lead you to check the output at the regulators. An easy mistake to make is a diode the wrong way round.
 
If the power at the opamps is OK, you need to check the connections from the input jack to the first opamp, from the first opamp to the second pair of opamps (remember there's a cap and a pot in between) and from the second pair of opamps to the output jack if you haven't done this already.
 
If you haven't found a problem, now you can suspect a faulty component. The active components (opamps) are more likely to be problematic than the passives. If you have socketed the opamps you can swap in the ones from the working amp, but don't do this until you have checked the power.
 
Post again if you're not getting anywhere.
 
w

 

[BobSaysHi]

that's quite a post there.
 
Here's where I posted my problem, and it seems to be already solved.
http://www.diyaudio.com/forums/headphone-systems/193977-objective2-o2-headphone-amp-diy-project-91.html
 
The problem was probably excessive heat.
 

 

[francisdemarte]

Have you checked the regulator with a DMM to see if it's still working? These chips can take quite a bit of heat. I once removed a much smaller and more delicate usb controller chip that I thought was fried with lots of flux and a small kitchen blow torch. Turns out when I tested it, it was still working even after all that abuse.
 
 

 

[Pars]

Negative regulator? Wasn't an ST Micro part by chance was it? Have had problems with their negative regulators in the past. Use National/Fairchild/ON Semi instead.

 

[estreeter]

IF the Objective2 isnt the world-beater some of us thought it would be (for the money), its interesting that no-one has come forth to accept Voldemort's challenge. I guess everyone is just too damned busy with other things.

 

[BobSaysHi]

Quote:

Have you checked the regulator with a DMM to see if it's still working? These chips can take quite a bit of heat. I once removed a much smaller and more delicate usb controller chip that I thought was fried with lots of flux and a small kitchen blow torch. Turns out when I tested it, it was still working even after all that abuse.
 
 

How exactly would I check that with a DMM?
 
Quote:

Negative regulator? Wasn't an ST Micro part by chance was it? Have had problems with their negative regulators in the past. Use National/Fairchild/ON Semi instead.

It was an ON Semiconductor 
 

 

[francisdemarte]

Quote:

How exactly would I check that with a DMM?
 

http://www.ehow.com/how_7345520_test-to_220-voltage-regulators.html
 

 

 

[GLdgShDjKsHT]

just got my kit, now waiting to assemble it  
 

 

[cheapskateaudio]

I finally got around to A/B'ing my "modded" O2 with my semi-stock O2 and I was able to easily pick out the two amps in a blind comparison with matched volume levels. The only things not-stock on the the semi-stock O2 are the power supply caps, and the mosfets (I switched everything else back to stock). Mosfets are the same on both amps. If the filter caps were stock the difference would be even more noticeable, I just didn't feel like changing them, so, whatever... I also used the WAU16-400 for both amps, using the WAU12-200 with the stock amp would have increased the difference.
 
I preferred the modded O2 in everyway, which still isn't operating at 100% of it's best possible sound because I had to compromise on parts to fit them on the board and/or avoid burning things up like sissy v-regs, still, it embarrasses the stock O2, with its K-Mart blue light special parts selection... The sad thing is that maybe $5-$10 worth of upgraded parts can drastically change the sound of the amp, taking it from harsh and deafness inducing, to at least being listenable over a longish period of time.
 
The differences are blatantly obvious on some tracks, and more subtle on others of course. The biggest difference is the bass, there is simply more of it in the modded version. Measurements using REW confirm this, the bass stays hugely better controlled under 50 hz. There are other differences throughout the FR curve, but nothing that really says "this is the difference you're hearing" the way the sub 50z curve clearly does. 
 
 

 

[Willakan]

What do you mean by "bass control" exactly? I suppose it is entirely possible that your unmodded O2 is broken, especially with its propensity to fry regulators.

 

[cheapskateaudio]

 
Quote:

What do you mean by "bass control" exactly? I suppose it is entirely possible that your unmodded O2 is broken, especially with its propensity to fry regulators.

I mean that in REW, under 50hz, the FR curve is all over the place on the stock amp, and tightly controlled down to 20hz on the modded amp.
 
And yes, the regs get hot... I'm not sure how anyone could use the WAU16-400 and not feel that the regs are a tad hot, though they don't burn to the touch until a few hours have gone by. That's the nasty thing about heat, especially in a sealed enclosure, it saturates over time... Sure you check it after 30 min and it's ok, and it's a bit hotter after an hour, but check after 5-6 hours of music driving HD650's or something similar, with a hot input, and charging batteries. If one was to leave the amp on 24/7 with the WAU16-400 I'm pretty sure the v-regs will burn up or significantly degrade within mere weeks or possibly days.