neutralzz 0 Report post Posted November 22, 2005 this might make a difference.. but its dam big.. Share this post Link to post Share on other sites
squalle 0 Report post Posted November 23, 2005 LOL that's called killing an ant with elephant rifle with that kinda s ize, I gotta hunch telling me that somehow it'll give some problems too Share this post Link to post Share on other sites
jasonhanjk 0 Report post Posted November 23, 2005 Ouch. Very BIG!!! Digital pot is another study and is used differently from standard pot. You must only use them for single supply only (unless they are design to use dual supply). Which one sound better, I don't know. If you have an analog pot that is 50k but min resistance is 100 ohm. In terms of dB is -0.017. You won't hear any difference. Share this post Link to post Share on other sites
kross 0 Report post Posted November 24, 2005 hi guys, you guys experience any popping sound when u on/off the cmoy? i have this problem so dunno how to get rid of it. Share this post Link to post Share on other sites
matt.pimm 0 Report post Posted November 25, 2005 Hi, I think on-off popping might just be a feature of the amp. There is no output isolation to stop this effect. I think it is assumed by most to disconnect your cans whilst switching on and off with the volume at minimum, then connect cans. Hope this helps Matt Share this post Link to post Share on other sites
squalle 0 Report post Posted November 25, 2005 it might be due to the op-amps being on/off or vice versa or might be the DC offset causing it have u measured for DC offset at the output? Share this post Link to post Share on other sites
kross 0 Report post Posted November 25, 2005 din measure. will measure when my multimeter is ok. i'm using batteries. Share this post Link to post Share on other sites
jasonhanjk 0 Report post Posted November 26, 2005 It's always best to plug in your headphone when the unit is on and plug out before off. Share this post Link to post Share on other sites
klernie0521 0 Report post Posted November 26, 2005 (edited) Newbie question here. I have completed my cmoy2 amps but the right side doesnt have signal. I thought the problem came on the op amp for ground so i by pass it but no luck Any ideas what is the cause of this problem and how i can make it function? btw i used 0.1uf 63v cap rather than 1.0uf 63v. http://img494.imageshack.us/my.php?image=front5jw.jpg http://img494.imageshack.us/img494/9052/back5hb.jpg Edited November 26, 2005 by klernie0521 Share this post Link to post Share on other sites
neutralzz 0 Report post Posted November 26, 2005 your soldering's in big blops.. try to check whether any points have been shorted Share this post Link to post Share on other sites
heady 0 Report post Posted November 26, 2005 Did you clean the flux off the board before testing? And what op-amps are you using? Share this post Link to post Share on other sites
klernie0521 0 Report post Posted November 26, 2005 op amp used opa2314 and LT1077CN8 Haven't clean the flux before testing. Newbie question, what do i use in cleaning the flux? This is my first time assembling electronic parts (particular soldering) Thank you very much for bearing with me Share this post Link to post Share on other sites
1bit 0 Report post Posted November 26, 2005 hi klernie, welcome to sgheadphone! to troubleshoot the no signal problem on the right channel, the first thing come to mind is to check the connection for the right channel as also suggested by neutralzz. there are two possibilities: one or more component of the right channel is shorted to ground, or some where along the right signal path there's a poor soldering. check for these problems using continuity tester on your multimeter. i can't see clearly from the picture but the soldering on the pot looks suspicious to me, check for short from the wiper to the ground pin for the right channel. if the connections in the right signal path is ok, check the soldering for the power and ground pin for the right channel opamp ic (but it looks alright from the picture) if the connections on the pcb are fine, check the connection off-board i.e. the soldering on the input/output jack. the right channel could be shorted to ground there. if there's no connection problem, the components might be faulty. check the opa2134 by interchanging it. if the problem only persist on the right channel, the ground opamp should be okay as if it has gone kaput the left channel won't be working as well. but i think the ground opamp that you use (lt1077) is not suitable as it can only source/sink 5mA for the input capacitors (C1 and C2), i'd recommend you upgrade them to higher capacitances. with 0.1uF for C1 and C2 and 10kohm for R4 and R8, the cut-off frequency is around 150 Hz. you'll be missing all the bass like this. 0.1uF for the bypass capacitors (C3,C4,C5) would probably be enough btw heady, how do you clean the flux off the pcb? where can you buy flux cleaner? Share this post Link to post Share on other sites
1bit 0 Report post Posted November 26, 2005 forgot to add: be careful if you want to change the input caps, the soldering pad on the pcb could fall off Share this post Link to post Share on other sites
heady 0 Report post Posted November 27, 2005 (edited) All solders I have used deposit this greasy oil on the PCB. I am told this is flux and is conductive, so it can short the solder points. I use surgical alcohol to clean the PCB after soldering. I pour some into a small dish and use a toothbrush to scrub the PCB. You can get the alcohol from pharmacies, chinese medical halls etc. Actually the recommended alcohol is supposed to be purer than this commonly available surgical alcohol but that is hard to get. I have used the 75% alcohol (25% water) commonly available as surgical alcohol and have had no problems so far. After cleaning, you need to dry the PCB. I sponge off the excess with paper towels and then use a bulb blower to blow the alcohol from under components. Then I use a hair dryer on low setting to dry the PCB. Note that alcohol is flammable and if not careful, using a hairdryer may set it aflame. Skip the hairdryer if you are worried. Edited November 27, 2005 by heady Share this post Link to post Share on other sites