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The Objective2 (O2) Headphone Amp DIY Project
The Objective2 (O2) Headphone Amp DIY Project
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Old 30th March 2012, 07:58 AM   #2291
sofaspud is offline sofaspud  United States
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I think RS mentions that you should use discharged batteries for this purpose. I suppose it wouldn't matter so much if I hadn't already populated the board apart for the mosfets. What do you think? Risk it?
I don't recall what RS wrote. I think "should" may be overstating it a bit. With the switch off, there won't be any current flow. If there's no current flow, does it make any difference whether the battery is charged or discharged? Not to me. Not to the battery or the O2, either. What you need to be aware of is: 1) As I mentioned, make sure the switch is off and the AC adapter isn't plugged in (I'd hope you're doing that virtually any time you solder!) and 2) The battery will act as a heatsink when you try to solder, making things potentially more difficult.
Get the terminals positioned and solder only the farthest pin from the battery. At this point you only want a good enough hold so that you can disconnect the battery. After you've done that, put a good solder joint on the other 2 pins and then go back and resolder the first pin.
On second thought, reconsidering the 3-pin terminal, it's probably easiest to solder the 2 farthest pins before disconnecting the battery.
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Last edited by sofaspud; 30th March 2012 at 08:05 AM.
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Old 30th March 2012, 03:19 PM   #2292
ethanolson is offline ethanolson  United States
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FWIW, I just soldered two wires straight on to a new and live 2016 lithium cell battery for a project last week, had a bad solder joint and reflowed it and the battery got super hot... didn't hurt a thing and everything works great.

Alkaline is much safer, there's nothing that will happen that will jeopardize your safety or the O2, so even if you have an undesirable event, you'll be fine and you'll move along much faster in your project if you just connect the things and go. You've already accepted the demise of your battery... have at it. The worst that could happen is the battery might split or buldge if you short it for a LONG time. Even if that happens, you can still proceed with your project as planned. It's just an alkaline battery.
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Old 30th March 2012, 05:35 PM   #2293
nezbleu is offline nezbleu  Canada
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The Objective2 (O2) Headphone Amp DIY Project
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Originally Posted by sofaspud View Post
I don't recall what RS wrote. I think "should" may be overstating it a bit.
I don't disagree with you, but RS is pretty clear on NwAvGuy: O2 Details under "Cautions":

A dead disposable battery is highly recommended to clip into place before soldering the terminals but don’t try using a “live” battery

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Old 30th March 2012, 06:09 PM   #2294
ethanolson is offline ethanolson  United States
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Oh... to clarify my last statement a bit, if you have the opamps and mosfets populated, then don't use a live battery. For now, it appears that you're good to go forward. I do think RS took the right blanket approach, proving that not all US citizens are cowboys like me.
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Old 30th March 2012, 08:18 PM   #2295
lorriman is offline lorriman  United Kingdom
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Well, I tried the non-discharged battery and I am unhappy to report that the consequent explosion blasted off my front porch and veranda, and moments later my eye brows fell off. I never liked that veranda, but the loss of my brows is something of a blow as I had been carefully tending them over the last month. Obviously I will have to sue the pants off everyone involved in this fiasco. I hope you have nice pants, Sofaspud and Ethanolson. I prefer corduroys.
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Old 30th March 2012, 09:30 PM   #2296
ethanolson is offline ethanolson  United States
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I think we managed to get you on the UK's terrorist watch list; what with the explosions and uncouth brow removal technique.

Let me check...

...nope. Maybe give it a day for the block cameras to be reviewed by "staff."

But I see the backlog at the Ministry of Justice for criminal injuries compensation is rather to my favor at the moment.

Last edited by ethanolson; 30th March 2012 at 09:39 PM.
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Old 30th March 2012, 09:31 PM   #2297
sofaspud is offline sofaspud  United States
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If anyone does not understand my instructions, they need a porch to stay on.
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Old 30th March 2012, 10:36 PM   #2298
Yangoran is offline Yangoran  United States
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I have some extra O2 stuff up for auction on eBay if anyone's interested. Look for item #140732629263.

Also I have some custom engraved stainless steel front panels coming back from a machine shop right now; I'll post pictures up here once they arrive. I got two of these custom made for $34 each so perhaps I'll post the second one up on eBay if anyone's interested.
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Old 31st March 2012, 09:44 AM   #2299
lorriman is offline lorriman  United Kingdom
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Well, I stuck my eyebrows back on with a bit of super-glue, so all is forgiven. And thinking about it I really don't need another pair of corduroys.

In the meantime I have a serious problem.

I reached the testing stage. It passed the resistor test. However when I did the very first test (AC power, u1-u4 out, power-switch off, test voltage at battery terminals) I got the wrong voltage, 17 instead of 23-24, and the four large capacitors warmed and slightly bulged?!?!?! I left the power in for 5 seconds at the most. I actually didn't notice the capacitor bulge/warming until after the second attempt. The bulge isn't exaggerated but my unused capacitors (I have spares) have dead flat tops.

I can barely believe it but I do seem to have hit the jackpot in terms of disaster builds.

I can think of one possible reason for this: the o2 was sitting on my anti-static mat when I did this. Presumably it's a conductor and I just shorted the whole device. I've examined the whole of the back of the board with a loupe for solder bridges but can't see any.

Any opinions as to whether it is salvageable? Presumably the electrolytic capacitors are goners. The two smaller electrolytics look fine and didn't warm up. Nor the regulators. I have two more kits for making two more o2's. But I would rather not embark on that until I've established what elementary mistake I made.
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Old 31st March 2012, 10:18 AM   #2300
lorriman is offline lorriman  United Kingdom
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...I should add that at one point, after the initial failed test, I accidentally put the power in with the device switched *on*. It was only for a couple of seconds but evidently if the power circuit is screwed then I may have killed the amp circuit as well. The LED did come on.
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