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Yet another CMoy Thread...

post #1 of 15
Thread Starter 

Hey, so after having a problem with a Ventus EZ, I decided to build a CMoy.

 

Turns out, the issue i'm having is quite similar to the ventus issue in a way.

 

I have checked my solder joints, and am pretty confident they are not the issue.

 

The amp distorts pretty badly, it seams like its worse with lower notes, but I can't be sure. Also, unless the volume is at about 90% on the CMoy, the channels are unbalanced. Infact, when the volume is low on the CMoy, sound only comes out of the left channel. I have checked the current draw, .007a and each measured V+ to GND, and its 4.64v so that isn't the issue I don't think.

 

Any help would be greatly appreciated! Thanks!

post #2 of 15

As always, some nice, clear pictures would help us to help you

post #3 of 15
Thread Starter 
Coming once I find a camera smily_headphones1.gif

Also, I soldered directly to the OpAmp, so is it possible I fried it. I didn't remember that OpAmps can fry, so I didn't pay attention while soldering
post #4 of 15

It is possible to fry it with too much heat.

If you have your iron too hot or linger on the pin for too

long it will damage the internal physical structure of the op amp.

Thats one reason it's good to use an IC socket for a beginner.

It also makes it much easier to roll op amps later.

 

The down side is that higher performance op amps may become

unstable if used in a socket.

 

Op amps with performance similar to OPA2134 are perfectly

happy in an IC socket.

post #5 of 15
Thread Starter 
Quote:
Originally Posted by Avro_Arrow View Post

It is possible to fry it with too much heat.

If you have your iron too hot or linger on the pin for too

long it will damage the internal physical structure of the op amp.

Thats one reason it's good to use an IC socket for a beginner.

It also makes it much easier to roll op amps later.

 

The down side is that higher performance op amps may become

unstable if used in a socket.

 

Op amps with performance similar to OPA2134 are perfectly

happy in an IC socket.


How can I test if the OpAMP is fried?

post #6 of 15

Check the DC offset and current draw.

 

http://tangentsoft.net/audio/trouble.html

post #7 of 15
Thread Starter 

Current Draw was .007 Amps

DC Offset from my Cowon was 0 Volts both channels.

 

BUT, coming out of the CMoy, right channel (ring) was 0 mV, while left was between 90 and 250 mV, it would stop moving throughout that range, so I couldn't get an exact #
 

post #8 of 15
Thread Starter 

Thats with the knob all the way down (minimum volume)

 

However, with max volume, I decided to plug it into my Lyr, which obviously has a higher input impedence than my 32 ohm K167's, (I don't have a 1/4 to 1/8 so I cant test my higher impedence cans), The distortion is totally gone. Obviously it distorts a bit from double amping but that distortion is almost totally gone. So i'm thinking this is only an issue with lower impedence phones maybe?

post #9 of 15

Dutch -You dont give up do you?-Posters including myself said you should spend some time on learning basic electronics.

           If one channel has an offset that varies as much as you say[on DC] then the chips fried.

               UNLESS you have made a bad job of soldering.

                  Current draw is okay in no load but knowing the number of faults on ICs that can occur I still think its faulty.

                     Avro is right -Why didnt you solder in an IC holder would make life easier for you-they are very cheap ones.but better get high impact plastic with gold contacts[industrial version]
 

post #10 of 15

Ok, so I'm going to try to give good advice one last time.

 

See this...

 

 

That's the first Cmoy that I built way back in 2004.  It's was horrid.  And yet, it worked.  Why?  Probably I got lucky.  But I posted that image way back then and someone stepped in and said, "Hey Nate, you're soldering is pretty crappy.  You should really practice some more before you start trying to build any bigger projects."  Or something like that.  So I went out and bought some more of that pcb material from Radio Shack and instead of burning the $ that it would been to build full CMoys I just worked on creating boards with the proper jumper arrangement.  5 months or so later I'd gotten quite a bit better and built a PIMETA.

 

 

While not text book the soldering work there looks a lot better. 

 

I built small surface mount projects, low voltage tube based projects, more opamp based stuff like the M³ and PPA and so on a so forth.  At each step along the way I built my skill set.  At this point I think it's pretty clear that you need to work on your basic soldering technique if you want to quit throwing money away.  So do your self a favor, go out and buy a big piece of perfboard and cut up some copper jumpers from junk wire and practice just soldering those in place until you get a good looking joint.  Until you can do that there's just no sense if working with actual parts unless you want to hope that you'll get lucky and not burn something up.  I'm glad to hear that you had the good sense to test the DC offset before plugging in your headphones.  But that should have made a little light go off and told you that maybe you need to learn to walk before you can run.

post #11 of 15
Quote:
Originally Posted by n_maher View Post

Ok, so I'm going to try to give good advice one last time.

 

See this...

 

 

That's the first Cmoy that I built way back in 2004.  It's was horrid.  And yet, it worked.  Why?  Probably I got lucky.  But I posted that image way back then and someone stepped in and said, "Hey Nate, you're soldering is pretty crappy.  You should really practice some more before you start trying to build any bigger projects."  Or something like that.  So I went out and bought some more of that pcb material from Radio Shack and instead of burning the $ that it would been to build full CMoys I just worked on creating boards with the proper jumper arrangement.  5 months or so later I'd gotten quite a bit better and built a PIMETA.

 

 

IT BURNS MY EYES!!!

KILL IT WITH FIRE!

post #12 of 15
Thread Starter 
Quote:
Originally Posted by nikongod View Post

IT BURNS MY EYES!!!
KILL IT WITH FIRE!

Lol alright I guess practice mass perfect, so done with kits for now

If only I was as good at pcb as I am at soldering connectors :/ haha
post #13 of 15

Did anybody explain how to solder?

 

People think, 'Soldering. How difficult can that be?'

 

The answer is, 'As difficult as you want to make it...'

 

The fact is, there's a wrong way to solder, and that's the way most people instinctively try first.

 

You DON'T melt solder onto the soldering iron and try to get it to stick to the items you're trying to solder. This is GUARANTEED not to work. Why? Because the flux core of the solder will no longer be effective by the time you get the solder to the surface you are trying to solder.

 

You need a soldering iron and rosin-cored solder.

 

When you get the soldering iron, you turn it on for the first time, that's when you melt solder onto it. You turn it round and round and push the solder onto it and make sure that every part of the tip has a thin shiny coat of solder. This is called tinning. Ignore any drips that form and fall off. Then you wipe it on the wet sponge (you did wet the sponge?) on the solder station, or wipe it on a damp rag. Be careful if you use a rag, steam will form and if the rag is not thick enough (folded) you will get burnt. Wipe off all the drips of solder and any flux.

 

Everything you're trying to solder together must be clean. This means shiny clean. If it's copper, like perfboard, you need to polish it with emery paper (sandpaper) unless it is brand new. Components are treated to stay solderable for a while, but even they will not stay good for soldering for ever. A layer of oxide forms with exposure to air. YOU CANNOT SOLDER THROUGH IT. You may have to clean them with emery paper too. With resistors you fold the paper round the lead, hold it tight and pull it off the lead. Do this a couple of times to make sure the metal is exposed. Otherwise you can scrape the leads with a scalpel or craft knife blade. If you are unsure whether the part is clean you can check by pre-tinning it. Heat the LEAD with the iron, push the solder onto it, and check that the solder forms a thin film on it, just like the tip of the iron.

 

When you have inserted a component into the board, you push the tip of the soldering iron into contact with the lead AND the copper on the board. The tip must be tinned, but not dripping with solder. After a couple of seconds you push the solder (wire) into contact with the LEAD and the COPPER on the board. If you can get it to touch the tip simultaneously, so much the better. Make sure the solder flows onto the copper pad and the lead. If it forms a ball or puddle the joint is not wetted. The solder must wet the joint for it to be effective. You can see the instant when the solder collapses and goes from sitting on the surface to actually wetting the joint. You MUST be able to see that the solder slopes onto the parts and board gently and does not sit up like raindrops on a dry window. It should look like a little volcano with the lead sticking up out through the peak.

 

Remove the solder from the joint, remove the iron from the joint without disturbing the parts, blow gently on it if you like to cool it. Wait until you see that it has set or you will have to reapply the iron, because a joint that has been disturbed in the process of setting may fail.

 

Job done. Move on to the next joint.

 

w

post #14 of 15

The tangentsolft webpage has a few crash course tutorials in soldering:

 

http://tangentsoft.net/elec/movies/

post #15 of 15

Didn't know that. No harm done I guess.

 

w

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