HELP on cmoy amp needed

[feesh 0]

Hi,

 

this is my first DIY headphone amp attempt. i've followed the circuit and instructions from both tangentsoft and williamneo.blogspot.com however i'm facing certain difficulties. i was wondering if you diy audio pros can help explain/debug the problems i'm facing. i'm using a national LM4562 op amp.

 

the problems are

#1: i'm only getting audio from my left channel. is the audio jack i'm using the correct one?

#2: the audio from the left channel sounds wonderful, but it only lasts 3.5 seconds. after that, the volume goes all the way down to near inaudible.

 

i've attached pictures to what i've built so far. i've been trying to debug the problems for quite some time now, i really need the help of you kind souls out there.

 

thanks in advance!

 

[heady 0]

Hi feesh,

I think you did a good job for a newbie. I think the problem is probably related to your soldering and maybe also to your interpretation of the circuit.

 

I built at least two CMOY before I succeeded with my third. So definitely you are just starting. The pictures are rather limited and not helpful in this instance.

 

Re: soldering, it is always easier if you use some additional flux before you solder. You will find you need less solder and it will be nicely rounded.

 

I also find stripboards easier to implement a cmoy design than the protoboard you used. The strips of copper will replace many of the wires and lessen the risk of shorts etc.

 

After soldering, you need to remove the flux before testing and it is especially important to measure DC offset before testing with earphones, if you want your earphones to survive.

 

Cheers.

 

[feesh 0]

thanks heady,

 

so heady, the parts i used are correct? my audio jacks look very different from everyone else's. its not a mono audio jack right?

 

maybe i'd go down to slt again to find the stripboards you mentioned. and what do you mean by additional flux? isnt the soldering lead already filled with flux?

 

sorry if its a newbie question, cause afterall, i AM a noob.

 

thanks again

[loop_ 0]

i say this at risk of offending you...but your soldering is really ugly! Kudos nevertheless for working without a pcb, which I don't dare to do...

 

it's not just an aesthetic concern; alot of the solder joints look like cold solders - looks like there isn't a good connection in a few of those. also, some of the soldering looks so thick that you might have a situation whereby wires which are not supposed to be touching each other are.

 

Alot of diy problems come from poor soldering, so this might be a good place to start. One suggestion is to use a multimeter and do continuity measurements across all the wires.

 

I found this guide very useful - http://www.amb.org/audio/basic_soldering_tips.pdf

 

 

[alamakazam 0]

they look worst than my micromouse

 

http://www.youtube.com/watch?v=X0GmsnE9QFw

 

try this type of board, but you need to plan ahead and drill the copper board away

 

Edited March 20, 2008 by alamakazam

[feesh 0]

i say this at risk of offending you...but your soldering is really ugly! Kudos nevertheless for working without a pcb, which I don't dare to do...

 

it's not just an aesthetic concern; alot of the solder joints look like cold solders - looks like there isn't a good connection in a few of those. also, some of the soldering looks so thick that you might have a situation whereby wires which are not supposed to be touching each other are.

 

Alot of diy problems come from poor soldering, so this might be a good place to start. One suggestion is to use a multimeter and do continuity measurements across all the wires.

 

I found this guide very useful - http://www.amb.org/audio/basic_soldering_tips.pdf

 

lol loop_

 

i take that as a constructive criticism. it is afterall my first time soldering as well. i never thought soldering would be so difficult but hey, we all have to start somewhere. thanks so much for the tip and link. the link you gave me is really useful and i appreciate your help. shall try again.

 

thanks (:

 

to: alamakazam

 

is this the stripboard heady was talking about?

[heady 0]

feesh, that is a stripboard type of protoboard. With proper design, there can be minimim of wires going around. Draw your design on paper and post an image here and we will try to help you get the design right.

[feesh 0]

feesh, that is a stripboard type of protoboard. With proper design, there can be minimim of wires going around. Draw your design on paper and post an image here and we will try to help you get the design right.

 

okay so i've bought a stripboard. and i've spent some time planning it. purple crosses represent soldering joints, R = resistor, C = capacitor and the pink dots represent the copper that i have to drill away. i didnt include the wires that will connect the cap to the batteries/led. i will not be using the 47ohm resistor on the feedback loop. i think it might work but what do you guys think?

 

 

thanks again!

Edited March 21, 2008 by feesh

[williamneo 0]

Hi! feesh, Thanks for visiting my site tutorial! ur descripiton sound like ur capacitor somehow has short circuit or bad soldering connection. Don't rush to complete the work, take your time slowly solder your connection. (not too slow till burn ur component and stuff) but focus, alway position your circuit board in a way you feel comfortable and secure b4 u point your iron on it. Take care! and good luck!

[feesh 0]

Hi! feesh, Thanks for visiting my site tutorial! ur descripiton sound like ur capacitor somehow has short circuit or bad soldering connection. Don't rush to complete the work, take your time slowly solder your connection. (not too slow till burn ur component and stuff) but focus, alway position your circuit board in a way you feel comfortable and secure b4 u point your iron on it. Take care! and good luck!

 

nah, i should be the one thanking you. i think your tutorial is more extensive that the one at tangentsoft.

 

okay so i've made another new cmoy based on my new circuit design. IT WORKS! however, only at high volumes. at volume 15, the volume doesnt drop after 3.5secs. if i go any lower than 15, the output just dies. do you think that the lm4562 is special in which in needs a high input signal to work properly? this will create a problem as when the song track changes, there would be no input signal, resulting in the reduction of volume + distortion/clipping. should i reduce the gain?

Edited March 22, 2008 by feesh

[williamneo 0]

Sorry Feesh as for the Lm4562 i have never try it before so i am not sure how it work and the compatible of it. I actually have done up one more cmoy instruction you may one to take a look see if this could help? http://williamneo.blogspot.com/2008/03/mos...on-on-cmoy.html

[feesh 0]

its okay. i tried looking up for people who built the cmoy around the lm4562 but couldnt find many. only one, so i suppose it is quite possible. i just ordered a tle2426 and an opa2132. gonna see if its my soldering or the chip thats not compatible. although from common sense, i think its the capacitors thats causing problems. but we'll see.

 

thanks williamneo. (: i think your blog is good place for beginners like me to start. will try the RA1 when i finally get my cmoy up and running.

[williamneo 0]

Good Luck!

[loop_ 0]

any update?