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apheared 47... HELP!!!

post #1 of 5
1/14/12 at 11:32am
Thread Starter 

So i got the circuit lookin all fancy n such, then i powered it up (no chips in place) and then the issues started. In its current state, without chips, the positive rail voltage starts at around 18V and slowly makes it way down to about 11.8V and the negative rail starts at about -5V and slowly works its way up to about 11.8V. I'm using a 24V wall wart. the power circuit started as an active ground channel from tangents tutorial, then the tle2426 fried even though it was working properly. i tried using a buf634 for the ground channel but that wasnt giving me good results...so now i'm using the basic resistor divider power supply and this gives me the described bahavior.

 

Based on the activity of the rails my guess is that a capacitor is charging slowly? maybe i put a higher value resistor in front of one of the caps? Idk...guess thats why i'm here seein if anyone knows how to fix this.

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post #2 of 5
1/14/12 at 12:06pm

Pics would help, as well as a link to what schematic you are using. I'm guessing you might be going from this one?

 

http://benfeist.com/a47/default.asp

 

One thing to check: polarity of your power caps which I guess you have following the tle2426 or the voltage divider resistors. The cap for the negative rail should have the "+" terminal connected to virtual ground; the V- is more negative than ground is.

 

You can do a google search using a47 site:head-fi.org which might pull up other threads also.

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post #3 of 5
1/14/12 at 12:33pm
Thread Starter 

i was using this amp schematic:

 

http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=apheared_prj.htm

 

i was using the last power schematic on this page...but now i'm using the second:

 

http://tangentsoft.net/elec/vgrounds.html

 

i made sure the power caps are in properly. i checked all the resistor values.

 

doing a search showed me other people problems...but nothing like mine.

 

I can post pictures if you really want but the whole circuit is a mess due to much trial and error. the amp section is pretty clean but the power section has wires goin everywhere.

 

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post #4 of 5
1/14/12 at 12:55pm
Thread Starter 

What happens if i change the resistors in this picture to something like 10K instead of 4.7K?

 

rdiv.png

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post #5 of 5
1/14/12 at 2:29pm
Thread Starter 

now i feel like a nub asking for help but i was lookin at it for hours. forgot to wire the output to the non-inverting input on BOTH CHANNELS. even fixed the power circuit so it now has the buf634. however there is still one small issue. when the power is on there is no noise. but when the power is off there is a buzzing sound. I tried to fix this by putting the off position of the switch to ground which solved the problem, but then introduced a loud click sound when powering off the amp. any ideas how to stop the buzzing when the amp is off? it doesnt make sense to me because there should be 0V on the power when the switch is off...

 

and i'm using this power supply, but not a battery...

 

buffer.png


Edited by crepuscular457 - 1/15/12 at 4:36pm
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