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Cmoy first build questions
Mar 21, 2011 at 5:31 PM Post #47 of 60
right left no1 for now and made no2. was working quite well, but then one channel stopped :frowning2: i tried another op amp but no joy. the phones are fine.
any ideas? i will get some pics soon.
 
also i got some 50k audio pots, and changed r2 to a 520k carbon resistor (all i had)
 
one thing i have noticed on both my cmoys tho is that the sound is good at low volume, but as soon as it is slightly loud (less loud than it would be non amplified) the sound distorts and goes crappy. could this be due to the gain of 11?
Rob
 
Mar 23, 2011 at 4:53 PM Post #48 of 60
Ok, i have some pics. i know the resistors are huge! i wish i got some 1/4w not 2w now :/
 
IMG_0130.jpg

 
IMG_0129.jpg

 
IMG_0128.jpg

 
IMG_0126.jpg

 
IMG_0131.jpg

 
IMG_0131.jpg

 
IMG_0124.jpg

 
IMG_0123.jpg

 
IMG_0122.jpg

 
IMG_0120.jpg

 
IMG_0119.jpg

 
IMG_0118.jpg

 
Turns out there is faint sound in the left channel ( i think) and full sound (low quality... like this in both, is this cos of the gain, or a fault?) in the right. (will lowering the gain or putting in r5 remove distirtions, or is it due to the component quality, etc? it doesnt even get to normal ipod volume before going distorted on bass hits :frowning2: )
 
the sound gets a bit louder in the left when i touch the pot and the left input on the pot, but not much.
 
any suggestions??? i dont want to end up with a crappy amp, as that would defeat the object!
Plz help!
Rob
 
Mar 23, 2011 at 4:56 PM Post #49 of 60
Ok, i have some pics. i know the resistors are huge! i wish i got some 1/4w not 2w now :/
 
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0130.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0129.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0128.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0126.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0131.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0131.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0124.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0123.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0122.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0120.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0119.jpg
 http://i695.photobucket.com/albums/vv312/r_chez_08/Cmoy/IMG_0118.jpg
 
 sorry you will have to click on them, the codes were playing up?
 
Turns out there is faint sound in the left channel ( i think) and full sound (low quality... like this in both, is this cos of the gain, or a fault?) in the right. (will lowering the gain or putting in r5 remove distirtions, or is it due to the component quality, etc? it doesnt even get to normal ipod volume before going distorted on bass hits :( )
 
the sound gets a bit louder in the left when i touch the pot and the left input on the pot, but not much.
 
any suggestions??? i dont want to end up with a crappy amp, as that would defeat the object!
Plz help!
Rob
 
Mar 24, 2011 at 6:45 AM Post #51 of 60
First thing, get some alcohol and clean up the bottom of the boards
 
use an old tootbrush
 
then you can see whats going on
 
Mar 24, 2011 at 6:21 PM Post #55 of 60
ok thanks. i will see if my mum can get me some, cos i doubt they will sell it to me, as i am 14.
For pics see above links.
The amp sounds really bad, so i will lower the gain, clean up with alcohol when i get some, and check for any solder bridges.
Rob
 
Mar 25, 2011 at 8:17 AM Post #56 of 60
From my lessons in 10th grade health or Biology class, humans cannot safely consume isopropyl alcohol as it will result in blindness or death...I think that you can readily buy it, but please don't try to drink it.  It would also be beneficial if you watch the Tangent tutorials on the Audiologica site, well good luck.
 
Hand sanitizer is 70-90% ethyl alcohol and isopropyl alochol can be found in sanitation wipes in high concentrations
 
Mar 25, 2011 at 8:39 AM Post #57 of 60
I've used meths it works but you need to scrub harder :)
 
cheers
FRED
 
Mar 25, 2011 at 5:47 PM Post #58 of 60
Ok thanks guys. I will see if we have any meths. Should it get to a shiny colour?
I replaced the gain resistor with 2.2k resistors. I now have a gain of about 5.5, and it aounds almost listenable!
I seem to have more sound in the bad channel now, approx 50% of what i have in te other channel.
Also another question, is it a bad idea to mix carbon and metal film resostors? Or is it unnoticable by intrained ears like mine :wink:
Finally, could the bad bass distortions be due to my headphones?
Thanks
Rob
Edit: 2v ish voltage differential between channels! Thisnmay be my problem. I thought i could have blown r4 or something, but both channelsnare the same.
 
May 21, 2011 at 1:33 PM Post #60 of 60
Ok i know it has been ages but i kinda left it for a bit. I thought it may have been a pot problem so soldered in a new pot, still 50% volume in one channel.
I then tested the voltages again. One reads just over 10v, the other 5v. They seem to change a bit when i plug headphones in.
The sound quality is good, just got this one problem. I cannot see any solder bridges.
Could this be a bad resistor or cap?
Rob
 
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