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Old 21st March 2013, 03:25 PM   #3211
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Quote:
Originally Posted by availlyrics View Post
Congrats-Keep up the good work. I read your blog, it reminded me of my school days when I had to borrow soldering iron from my friends to solder my broken h/p wires. Hope you build more such projects to finance your purchase of much needed measuring instruments.
Cheers!
Thanks!

Yes, in the beginning I had to borrow equipment from a neighbour. Last xmas my parents gave me my own soldering equipment so now I'm hoping to get enough customers to buy a better multimeter and some other stuff that's good to have.
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Old 25th March 2013, 07:48 AM   #3212
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Quote:
Originally Posted by tecnogadget View Post
...So besides the physical SIZE problem , can i use polyester caps without worrying about performance?
Go ahead with whatever is available locally,its better than using no-caps resulting large DC
BTW Gaincard by 47 labs uses 4.7 uF electrolytic i/p caps(I've read somewhere).
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Old 29th March 2013, 07:57 PM   #3213
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Here's a O2 powering PA spk. crazy

Objective 2 powering PA speaker - YouTube

Pls don't try this stunt on your B&W Nautilus
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Old 1st April 2013, 11:39 AM   #3214
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Default Thanks NwAVGuy, what a sweet package

Hey Guys, just want to share with you my accurate, none snaked oil HiFi environment, which - unfortunately for the notorious extravagant high end industry - wasn't too pricy.


Click the image to open in full size.

@ Engineer - where have you been? People need sane, down to earth discussions so they do not get detached :-)

KR
Tobias
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Old 9th April 2013, 05:56 PM   #3215
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Help!

Just built another O2 amplifier. Everything went smoothly except that I accidentally put a resistor in the wrong place but I fixed that before powering it up. Also the gain switch wasn't in a good position so I had to force it down a bit while heating up the joints.

Measured all voltages as the guide says and everything seemed fine.

Powered it up, connected a source and a pair of scrappy headphones. Expected it to work as it usually does but the sound was really distorted. Tried the headphones directly to my phone and then it sounded ok. I expected the gain switch to be the fault because it was a bit glitchy and I assumed I maybe broke it when pushing it down a bit. I have now removed it, it's broken to 1000 pieces and the sound is still as distorted as before.

I have checked the voltages at D1 and D5 and all seems fine.

Edit!

"Check pin 1 and pin 7 of U1. Both should be under 0.1 volts. If either is higher, check the pins of P1 with your source connected and turned on. There should not be more than +/- 0.02 volts at any of the P1 pins. If so, there’s a problem with your source. If P1 is OK, but pin 1 and/or 7 of U1 has significant DC, U1 is somehow developing a DC offset and either U1 is bad or there’s a soldering problem with it or all the parts around it."

Did this and when measuring from negative bt1 to pin 1 and 7 of U1 I between 200-350mV peaking at about 400mV. Is U1 faulty then? I see no solder bridges and I have reheated all the joints.

Please help me. This isn't my amplifier, I'm building it for someone else.

Edit2:
I have another JRC2903D because I have two sets to build. Shall I try with a "fresh" U1? Or is there a risk that I'll trash both because there's something wrong with the board?
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Last edited by Rullknufs; 9th April 2013 at 06:15 PM.
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Old 10th April 2013, 07:25 AM   #3216
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I tried with a fresh JRC2903D and the sound was just as bad as before.
I will take pictures of the amp this afternoon so you can see.
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Old 10th April 2013, 07:43 AM   #3217
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I would suspect the 2068 to be the culprit, had that before as well.

Good luck, Stefan
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Old 10th April 2013, 08:05 AM   #3218
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Quote:
Originally Posted by swalter View Post
I would suspect the 2068 to be the culprit, had that before as well.

Good luck, Stefan
Tried with a new fresh one. Same problem.

Edit: Oh god what an idiot I am! I had mixed up U1 and U2 so the 2903 was U1 and the 2068 was U2. Put them back correctly and now everything works as a charm. The only problem is I have trashed the gain switch by prying it loose from the board because I thought it was faulty. Is it some sort of standard component that I can find locally in Sweden? Or it is something that can be left off the board?
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Old 10th April 2013, 08:17 AM   #3219
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I don't know about parts availability in Sweden, but you can leave it off the board. Just pick what gain you want (no switch = no switchable gain) and jumper the connections. Use a cutoff component lead or piece of solid copper wire and it will be easy to remove and install a new switch at a later date.
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Old 10th April 2013, 08:24 AM   #3220
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Quote:
Originally Posted by sofaspud View Post
I don't know about parts availability in Sweden, but you can leave it off the board. Just pick what gain you want (no switch = no switchable gain) and jumper the connections. Use a cutoff component lead or piece of solid copper wire and it will be easy to remove and install a new switch at a later date.
Is it even necessary to jumper the connections? I have installed the standard gain resistors and now without the switch gain seems to be 2.5x. Might be 1x too though, not sure.
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