what did i do wrong?
May 15, 2003 at 11:54 PM Thread Starter Post #1 of 22

spott

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i just finished building my CMOY, and i can't seem to figure out whats wrong:
when i listen with my headphone plug in all the way one ear is loud, but the other is VERY quiet, however, when i put the plug in so that the ground of the socket is connected to the right chanel of the plug, and the left channel of the plug is connected to ground of the socket, the sound is fine loud in both ears, also there is nothing connected to ground.

what did i do wrong and where should i look for the problem? i built a CMOY with a linkwitz crossfeed filter.

thanks
 
May 16, 2003 at 12:12 AM Post #3 of 22
how... i built them on the same circuit board.... i've tries using the on/off switch for the crossfeed but it doesn't do anything.
 
May 16, 2003 at 12:28 AM Post #4 of 22
Have you checked the board for short circuits? I was killing myself the other day on my amp because of on tiny solder bridge. Even if you've checked, check again VERY carefully.
BTW, even when bypassed, crossfeed will still take out volume from the amp because some resistors are still in the circuit.
 
May 16, 2003 at 12:40 AM Post #5 of 22
its not that, only one channel is really quite, also, i've run a knife between all places that there could be a solder bridge.
 
May 16, 2003 at 12:54 AM Post #6 of 22
hi spott, what op-amp u r using? single or dual op-amp? i suspect something to do with the connections of op-amp....
wink.gif
 
May 16, 2003 at 12:56 AM Post #7 of 22
Quote:

Originally posted by spott
i just finished building my CMOY, and i can't seem to figure out whats wrong:
when i listen with my headphone plug in all the way one ear is loud, but the other is VERY quiet, however, when i put the plug in so that the ground of the socket is connected to the right chanel of the plug, and the left channel of the plug is connected to ground of the socket, the sound is fine loud in both ears, also there is nothing connected to ground.

what did i do wrong and where should i look for the problem? i built a CMOY with a linkwitz crossfeed filter.

thanks


Sounds a lot like you connected the input jack wrong, but any error there usually shows up as, "one channel works, the other don't." Also, if the crossfeed switch is off board, double check that the wires connecting it aren't swapped. Finally, if there is a volume pot in the circuit, make sure that it is working! Check the resistance from wiper to each leg as you rotate the knob.
 
May 16, 2003 at 1:01 AM Post #8 of 22
number one i'm using two single channel op amps, 123's i believe, also i've already checked connections, they are correct ground is connected to ground, right to right and left to left. i've looked over the board looking for unsymetrical wiring but can't find any... i have a suspicion (just that, a suspicion) that a resistor is dead, what does it take to do that?
 
May 16, 2003 at 1:07 AM Post #9 of 22
spott, i think a spoilt resistor is the last thing u should suspect....
tongue.gif
How about take a digicam and snap some pics of ur layout to us... maybe we can get a clearer pic of what's possible going wrong.....
smily_headphones1.gif
 
May 16, 2003 at 1:10 AM Post #10 of 22
Quote:

Originally posted by spott
.... i've looked over the board looking for unsymetrical wiring but can't find any... i have a suspicion (just that, a suspicion) that a resistor is dead, what does it take to do that?


It no longer sounds like there is a problem with the amp; rather, I'd check the headphones!

The odds of a resistor being bad - without having abused its I^2T rating, tried to yank it out of a board with needle nose pliers before unsoldering it, etc. - are so low that you have a better chance winning the lottery. I've never come across a resistor, straight out of the package, that was bad. SMT, high power, metal film, even crappy 30 year old carbon compositions (great for RF; not much else). Mechanicals are always the first suspect when something electromechanical goes wrong.
 
May 16, 2003 at 1:34 AM Post #11 of 22
o1.jpg

o2.jpg


heres two pictures. thanks for the help

[edit] picture size
 
May 16, 2003 at 1:35 AM Post #12 of 22
Quote:

Originally posted by jeffreyj
It no longer sounds like there is a problem with the amp; rather, I'd check the headphones!


its not the headphones, i've checked...
 
May 16, 2003 at 2:11 AM Post #13 of 22
wow...that's really a lot of wires coming out...
tongue.gif


Anyway, ur op amp section configuration seems correct, only one thing i'm not very sure, can u check ur inputs to op-amp? i mean input to the + of input capacitor and then - of the input capacitor to the +In of the op-amp... Try not to use pots first, connect the 2 wires (not ground) directly...

Do u have multimeter? Can u measure the voltages of V- and V+ of the op-amp? if ur voltages are almost the same but opposite polarity, then ur power supply and op-amp section is correct...

If power supply and op-amp are correct, bypass the crossfeed and try... to do this, unsolder the inputs to crossfeed and solder them directly to the inputs of the op-amp (the + of input caps)...

try this first...
rolleyes.gif
 
May 16, 2003 at 2:38 AM Post #14 of 22
.bmp's? ouch...

Go over the circuit very carefully with a multimeter, checking for continuity. Check input to output, input to ground, check everything that should be connected to ground and everything that shouldn't be connected to ground. Looking for solder bridges with a knife is good, but checking for continuity between two joints is better.
 
May 16, 2003 at 2:48 AM Post #15 of 22
theres more wires in the final, that was a version before i connected all the switches and the pot and mini jacks.

the V- and V+ of the op amps reads approx. 18 V, (i've got two 9V batteries connected)

i'm not sure what you mean... i THINK you want me to bypass the pot with wires; tell me if i'm wrong.
 

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