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Old 16th July 2014, 06:27 AM   #4031
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There is a via really close to gain switch. Check that it is not shorted to switch casing.
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Old 16th July 2014, 07:04 AM   #4032
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by zoidbergslo View Post
There is a via really close to gain switch. Check that it is not shorted to switch casing.
Thanks... I knew I'd seen mention of some issue somewhere.
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Old 16th July 2014, 07:07 AM   #4033
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by grogthegreat View Post
........Looks like Mouser put the wrong parts in the bag. I didn't measure each resistor before soldering it but I did match the manufacturer part number on each bag with the BOM.

Looks like I now have four new resistors to order!
At least you found the problem

If you want and while waiting for the parts, you can link out one resistor in each pair and see how it all sounds. It will be vastly different because 800ohms (400 with the pair) in series with the 'phones would be altering the damping and altering the response too.
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Old 22nd July 2014, 09:37 PM   #4034
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The new 1 Ohm resisters came in yesterday and I got them installed. What a huge difference! Amp is now working great. It gets plenty loud with no need for max volume or 6.5x gain.
I figured out why I didn't notice the 820 ohm resisters when I followed the initial resistance testing steps on the blog. My ohm meter was reporting the resistance as 0.819 k ohms. I didn't have the best lighting and failed to notice the 'k'. Since "0.819 ohms" was within .2 of 1 ohms I thought that I was good and moved on. Lesson learned!
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Old 23rd July 2014, 07:11 AM   #4035
Mooly is offline Mooly  United Kingdom
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Its easily done Great to hear that you have it all working OK
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Old 28th July 2014, 04:27 PM   #4036
jayb21 is offline jayb21  United States
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Ok so, I purchased the diy kit from jdslabs about a week ago. I constructed the objective o2 and once I got ready to test the amp there was no sound initially. So, after a friend took a look and told me I had some cold solder joints I went back and reworked those. I was then able to get sound from only one channel and that being the right. Now, I no longer have control over the volume with the potentiometer. Then, I though well let me touch up on some of the solder joint again. Upon doing so, I was able to get sound from the left channel and not the right and I was also able to have control of the volume via potentiometer. However, these issues still occur, I no longer have control over the volume and I can get no sound out of wither channel. Help and/or suggestions would be much appreciated.
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Old 28th July 2014, 05:24 PM   #4037
nezbleu is offline nezbleu  Canada
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Jayb21 have you gone through the checkout process? Are your DC voltages correct?

It sounds like you had no sound, then got sound in one channel, then the other channel, then no sound again, all by redoing your solder joints. If that is right, then one would have to assume that the problem is still with your solder joints, but until you can give some concrete measured results from the preliminary checkout process (measuring resistance and DC voltages) nobody can really help you.

Did the kit not come with the checkout procedures?
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Old 28th July 2014, 05:33 PM   #4038
Mooly is offline Mooly  United Kingdom
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I agree ^

We could go through a fault finding procedure but to do that efficiently and effectively would require a scope.

As it stands now I would do as nezbleu suggests and check your DC voltages. There is a comprehensive procedure for testing in a link at the bottom of post #1
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Old 7th August 2014, 02:24 PM   #4039
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Default Pcb Boards

Hi, Does anyone have any boards for these? I have had a look round but not seen anything available.
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Old 7th August 2014, 03:49 PM   #4040
agdr is offline agdr  United States
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Quote:
Originally Posted by m1n1man1275 View Post
Hi, Does anyone have any boards for these? I have had a look round but not seen anything available.
JDS labs in the US JDS Labs - Objective2 Printed Circuit Board / O2 PCB

Head'n'HiFi in Switzerland O2 Headphone Amplifier PCB

Note that both have a problem corrected. After NwAvGuy designed the O2 headamp Mouser stopped carrying the power jack that fit properly. Both these companies have boards that are adjusted to fit the available power jacks.
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