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cMoy Amplifier - Help a novice?

post #1 of 17
8/11/11 at 10:39am
Thread Starter 

So I've just started getting into electronic projects, I did a couple kits, and someone told me I should try a cMoy Amp. So I read about it and it seemed like a good little project for a novice. So I got all my parts from Radioshack (I know, I know. I also got the worst OpAmp ever, but I plan on replacing it, it's more there just so I can get this to work. Cost me a buck.) and then spent a day working on it.

I turned it on, and there weren't any over-heating issues. So I then plugged my iPod in, and used some cheap earbuds to test. There wasn't sound, so I turned it up on the iPod. Near the loudest, the music is very, very, very faint. And then If I max it on the iPod, it is a lot of weird noise, with chirps and scratches. Looking online it sounds like grounding issue. Some say to take a multimeter and test certain areas, but I don't understand where I'm checking.

I checked the V+ and V- to the ground spot, and it's coming out as 8.1 for V+ to ground, and 1.4 for V- to ground. I can't find a solder bridge anywhere though.

 

I have pictures, if you need another picture of something let me know and I'll get it. 

Also, I am following this guide.

Thank you for anyone who can help me figure it out!

 

http://i1123.photobucket.com/albums/l558/VoltageCaek/IMG_9517.jpg

 

http://i1123.photobucket.com/albums/l558/VoltageCaek/IMG_9516.jpg

 

http://i1123.photobucket.com/albums/l558/VoltageCaek/IMG_9519.jpg

 

http://i1123.photobucket.com/albums/l558/VoltageCaek/IMG_9520.jpg

 

http://i1123.photobucket.com/albums/l558/VoltageCaek/IMG_9521.jpg

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post #2 of 17
8/11/11 at 3:36pm

I've tried that guide before and failed. You need flexible wire and helping hands to accomplish that, and since your new you probably don't. I made the mistake of buying solid core and haveing no helping hands. Try this. It's much easier and better sounding.

 

http://www.jdslabs.com/diy.php

 

 

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post #3 of 17
8/11/11 at 6:45pm

I'm a novice myself, but it sounds like something is wrong with the power supply. The measurements should be about equal between V+ and ground and V- and ground, according to Tangent's guide. Can you post some pictures of the "other" side of the board (where the LED, switch and battery clip are connected)?

 

Really nice work so far, by the way. It looks a lot better than my first CMoy. 

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post #4 of 17
8/11/11 at 7:08pm

Have you cleaned the flux off?  Flux can bridge gaps without you seeing it.  Ive actually built that amp for my first project and got great results. Also check the audio jacks, the ones from radioshack suck.

If you want to upgrade get 470uf power caps the larger film caps .22 or .47uf will do you good, the opa 2132 or 2134 will be better too.

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post #5 of 17
8/11/11 at 7:39pm

Is that a dry joint?

 

IMG_9520.jpg

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post #6 of 17
8/11/11 at 8:15pm
Thread Starter 

@Fred_Fred2004

I checked that out, it's the negative for the LED power. But it was dry, so thank you for pointing that out. I fixed that up.

BTW I almost bought your kit on eBay. I apologize, I just wanted all the pieces same day. In the future I'll buy your kit if I end up making more amps for friends/family.

 

@John in Cali

I did that last night when I was reading about possible problems. It made the board a lot more clear, but it didn't fix or change any of the sound problems.

 

@Dan55

I'll get those pictures tomorrow morning. My camera is dead right now (Always dies at the worst times it seems)

If it is a power supply problem, what could be wrong?

 

 

 

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post #7 of 17
8/11/11 at 9:52pm

What opamp did you get?

 

cheers

FRED

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post #8 of 17
8/11/11 at 10:26pm
Thread Starter 

A terrible one, it was a buck and I only got it so it was operational.

 

It was either this one

http://www.radioshack.com/product/index.jsp?productId=2062547

 

or this one

http://www.radioshack.com/product/index.jsp?productId=2062598

 

I'll check in the morning which one it is, it's 1 am and I'm going to bed lol

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post #9 of 17
8/11/11 at 10:42pm

Ok both of those are single opamps and will not work, and that will be the problem

 

cheers

FRED

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post #10 of 17
8/11/11 at 10:46pm

Just had a look at Radioshack the only opamp I can see that will work is

 

http://www.radioshack.com/product/index.jsp?productId=2062594&filterName=Type&filterValue=IC-Analog

 

its not great but it will work

 

cheers

FRED

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post #11 of 17
8/12/11 at 8:35am

TL082 is always good to have for checking functionality.

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post #12 of 17
8/13/11 at 7:35pm

LOL TL082 is actually decent for audio. Not really what I would wish to have but it sounds better than most of the kids toys out there that use them improperly. Not that a C-moy is "proper" either. They should also have tl072. Both of those will work in a pinch.


Edited by rembrant - 8/16/11 at 10:02pm
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post #13 of 17
8/13/11 at 8:14pm

Radio shack dosent appear to stock very much now a days, the TL082 was the only chip I could see that would at least work :-)

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post #14 of 17
8/14/11 at 10:22am
Quote:
Originally Posted by Fred_fred2004 View Post

Is that a dry joint?

 

IMG_9520.jpg



where do you find these pcb's ? i thought of going from jds labs but the shipping refrain me (5$ pcb +6,50$ shipping). Can i make a JDS cmy from a pcb like yours ? Does people on head fi sell cmoy pcbs?

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post #15 of 17
8/15/11 at 12:56am

Thats just a piece of proto board, using Tangents tutorial its a doddle :-)

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