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Old 2nd November 2011, 06:48 PM   #621
MrSlim is offline MrSlim  Canada
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Can someone with a completed O2 measure the DC on the output P2 when one battery is pulled out? I suspect that 200mv would be wrong, but you never know..
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Old 2nd November 2011, 09:48 PM   #622
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I just did this to help someone at head-fi, and I also got 200mV with only one battery in. Both batteries in I get 3mV.
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Old 3rd November 2011, 02:03 AM   #623
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Originally Posted by HaroldHill View Post
Hi, all, First-time DIYer here. I have two questions I'm hoping you'll entertain. First, regarding the transformer: given the two transformers below and the default option on the BOM, which would be the appropriate choice when I'll be driving orthodynamic headphones (50 ohm) and low-impedance dynamic headphones? (Is there any reason for me to upgrade?)
What is the make and model of the two headphones... just to look up power handing and sensitivity? At 50mW per channel into 50 ohms that would be around 32mA per channel. Most likely the 16VAC 400mA transformer, but you might want to wait until RocketScientist logs in again to give you the best answer. Entirely possible that I'm missing something.
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Old 3rd November 2011, 02:28 AM   #624
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Originally Posted by diamonddustin View Post
I just did this to help someone at head-fi, and I also got 200mV with only one battery in. Both batteries in I get 3mV.
Ok, this test needs to be done with headphones in, I'll have to recheck tomorrow...
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Old 3rd November 2011, 02:39 AM   #625
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Hey guys,

So NwAvGuy confirmed that the measurements are within normal specs. He has updated the DIY Initial Testing section to clarify. I just wanted to pass this information along for anyone in the same boat as me.

Thanks to all who've responded. Time to get back to listening to this amp worry-free.

Good luck to everyone on their builds.
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Old 3rd November 2011, 04:47 AM   #626
orpheus is offline orpheus  United States
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Has anyone else had problems with the gain switch? I built two O2's the other day. One of them works fine, but the other doesn't work in high gain mode. I checked and rechecked and reflowed the solder joints. The only thing I can think that it might be is the switch, or a bad trace on the board. Is there anything else it could be?

I'm also having a different problem with both the amplifiers I built. I get an audible amount of crosstalk with both amplifiers, on both gain settings. When I play a signal through one channel, the signal is audible in the other channel, and gets louder when I increase the volume. Could this also be a problem with the gain switch? Could I have overheated the gain switches when I soldered and created the crosstalk problem?

Thanks to everyone for their suggestions, I appreciate your help.
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Old 3rd November 2011, 05:51 AM   #627
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Originally Posted by orpheus View Post
Has anyone else had problems with the gain switch? I built two O2's the other day. One of them works fine, but the other doesn't work in high gain mode. I checked and rechecked and reflowed the solder joints. The only thing I can think that it might be is the switch, or a bad trace on the board. Is there anything else it could be?

I'm also having a different problem with both the amplifiers I built. I get an audible amount of crosstalk with both amplifiers, on both gain settings. When I play a signal through one channel, the signal is audible in the other channel, and gets louder when I increase the volume. Could this also be a problem with the gain switch? Could I have overheated the gain switches when I soldered and created the crosstalk problem?

Thanks to everyone for their suggestions, I appreciate your help.
pull the switch off the board and test it with a multimeter, check to make sure you have proper continuity for the switch position, and make sure that you haven't melted any contacts together (though this is probably unlikely, still worth checking).

also check your board for solder that may be bridging two points that should not be connected.

check to make sure you haven't melted anything in the input or output jack that would make the two channels connect.
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Old 3rd November 2011, 06:40 AM   #628
Limp is offline Limp  Norway
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Quote:
Originally Posted by orpheus View Post
I'm also having a different problem with both the amplifiers I built. I get an audible amount of crosstalk with both amplifiers, on both gain settings. When I play a signal through one channel, the signal is audible in the other channel, and gets louder when I increase the volume. Could this also be a problem with the gain switch? Could I have overheated the gain switches when I soldered and created the crosstalk problem?

Thanks to everyone for their suggestions, I appreciate your help.
As the gain stage is in front of the potentiometer, I'd say the two issues aren't directly connected.
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Old 3rd November 2011, 06:59 AM   #629
Limp is offline Limp  Norway
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Old 3rd November 2011, 04:24 PM   #630
orpheus is offline orpheus  United States
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Thanks for your replies, I appreciate your help and suggestions.

The gain switch problem seems to have been a poorly soldered switch. I must have been too concerned about overheating the switch, so I under heated it. I began desoldering it to remove it, and once I saw how difficult that would be, I decided to resolder it. I then reflowed all the pads on the whole board, and the problem went away.

As far as the crosstalk goes, perhaps I am seeing a problem where there isn't one. I have to turn the volume up fairly loud, and I suspect that I wouldn't be able to hear the crosstalk if both channels were playing.

So far so good, I think this is a good sounding amplifier. I still have to put it through the paces, but it definitely drives my Fostex T50RP's better than my Mini3.

-Aaron.
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