[Rainmaker91]

   
My math says 11.2 ma at the 8.4V rating of the batteries (16.8V).  I still say you have it backwards.  LEDs are not "ON-OFF."  You will get a gradual, dimming glow all the way down to 0ma, almost.  The brightness is not proportional, either, which is why many of us select something in the range of 1/2 current rating to make them last forever. One-half current is still 75% brightness, or something like that.
 
If it's connected correctly, it's going to glow at some brightness level if it's getting the voltage you say.  Regardless of the voltage of the LED you selected, it's still rated for 20ma max - that's similar to every other LED made.

Yeah, I get what youre saying. Good to know it's not the resistor that is the issue then, but I cehcked and the LED is correctly wired. Maybe my sodering job was bad? I don't know, I'll test with some other LEDs I have laying around rated at 3.1v-3.4v and 20-30mA just to be safe. if that doesnt work then I'm going to try different resistors and get to the bottom of this (because it's annoying me a bit)
 
Also just noticed something strange with the amp, there is a slight "ticking" noise avery 1-2 seconds. Any clue what that could be?

 

[tomb]

 

   
My math says 11.2 ma at the 8.4V rating of the batteries (16.8V).  I still say you have it backwards.  LEDs are not "ON-OFF."  You will get a gradual, dimming glow all the way down to 0ma, almost.  The brightness is not proportional, either, which is why many of us select something in the range of 1/2 current rating to make them last forever. One-half current is still 75% brightness, or something like that.
 
If it's connected correctly, it's going to glow at some brightness level if it's getting the voltage you say.  Regardless of the voltage of the LED you selected, it's still rated for 20ma max - that's similar to every other LED made.

Yeah, I get what youre saying. Good to know it's not the resistor that is the issue then, but I cehcked and the LED is correctly wired. Maybe my sodering job was bad? I don't know, I'll test with some other LEDs I have laying around rated at 3.1v-3.4v and 20-30mA just to be safe. if that doesnt work then I'm going to try different resistors and get to the bottom of this (because it's annoying me a bit)
 
Also just noticed something strange with the amp, there is a slight "ticking" noise avery 1-2 seconds. Any clue what that could be?

 
I'm just guessing, but it could be a short in your soldering.  A capacitor might be charging/discharging and arcing through the short.  That would cause a ticking noise like what you report.  Chances are, it's the large electrolytic caps, because the film caps would charge/discharge much faster than that.
 
It might be the opamp oscillating, too, but that's usually a different type of sound.  Again, these are just guesses.

 

[Rainmaker91]

   
I'm just guessing, but it could be a short in your soldering.  A capacitor might be charging/discharging and arcing through the short.  That would cause a ticking noise like what you report.  Chances are, it's the large electrolytic caps, because the film caps would charge/discharge much faster than that.
 
It might be the opamp oscillating, too, but that's usually a different type of sound.  Again, these are just guesses.

I see, ill take a look at fixing that when i get time (got to work this weekend). Are you thinking its going to be around the caps themselves or anywhere in the circuit?

 

[MisterX]

Try some actual troubleshooting instead of guessing.
 
.
What's the idle current draw?
What's the reading when measuring voltage between the op-amp's pin 4 and ground?
What's the reading when measuring voltage between the op-amp's pin 8 and ground?
What's the reading when measuring between pin 4 and pin 8?
What's the power supply voltage?
What's the DC offset of the left channel?
What's the DC offset of the right channel?
 
IIRC tangent has a troubleshooting article if you need help on how to make any of those measurements.

 

[Rainmaker91]

  Try some actual troubleshooting instead of guessing.
 
.
What's the idle current draw?
What's the reading when measuring voltage between the op-amp's pin 4 and ground?
What's the reading when measuring voltage between the op-amp's pin 8 and ground?
What's the reading when measuring between pin 4 and pin 8?
What's the power supply voltage?
What's the DC offset of the left channel?
What's the DC offset of the right channel?
 
IIRC tangent has a troubleshooting article if you need help on how to make any of those measurements.

Agreed, it would be great to minimize the amount of guesswork.
 
I'll see about doing those measurements, but as I'm fairly new when it comes to electornics I might need some explanaion as to how to do these things. For the current draw would it work to just disconnect the switch and use those connection points to hook up the ampermeter?
 
As for the "DC offset" I'm not entirelly sure what you mean by this. Would this be the voltage measurements between the ground and left/right?

 

[MisterX]

Yes you can check the current draw by measuring amps across the switch terminals.
 
And yes again.....Measure the DC offset between the right or left output and ground.
(both tests are performed without the headphones plugged in and no music playing)
 
Also check that the op-amp is not getting hot when the amp is playing music.
 
http://tangentsoft.net/audio/trouble.html

 

[Rainmaker91]

  Yes you can check the current draw by measuring amps across the switch terminals.
 
And yes again.....Measure the DC offset between the right or left output and ground.
(both tests are performed without the headphones plugged in and no music playing)
 
Also check that the op-amp is not getting hot when the amp is playing music.
 
http://tangentsoft.net/audio/trouble.html

Nothing is getting hot I know that much, but I can do a measurement with IR if that would help. Honestly the only problem is the "ticking" sound other than that there is no background noise and it sounds really good (if a bit dark, but thats the OPA signature other than anything). the LED is an easy fix when I just figure out the problem.
 
I'll do the measurements jsut to be on the safe side though.

 

[MisterX]

The lead on the flat side (of the LED) connects to ground.
Probe it, got voltage across the leads chances are it's backward.

 

[Rainmaker91]

so... this is embarassing. I found another fault, there i a humming sound in the background when the amp is not hooked up to anything. I figured out what was the problem though, it's the soldering job I did on the pot. I knew it was lackluster, but I was convinced everythnig should work even though it all looks sort of shoddy. Anyway, I wiggled the wires on it and in doing so I removed both the ticking sound and the humming. I'll redo the soldering on it tomorrow, and I'll also check on the LED at the same time. I know you both have said it but I checked and the LED is not wired wrong, the connection may be bad but the anode and cathode are wired correctly. The positive current from the batteries are going in to the long round pin on the LED, which also happens to be the small pin inside the LED. The LED may be defective, or something that is far more likely my soldering job is bad. Either way I'll take a look at it after work tomorrow.

 

[tomb]

  so... this is embarassing. I found another fault, there i a humming sound in the background when the amp is not hooked up to anything. I figured out what was the problem though, it's the soldering job I did on the pot. I knew it was lackluster, but I was convinced everythnig should work even though it all looks sort of shoddy. Anyway, I wiggled the wires on it and in doing so I removed both the ticking sound and the humming. I'll redo the soldering on it tomorrow, and I'll also check on the LED at the same time. I know you both have said it but I checked and the LED is not wired wrong, the connection may be bad but the anode and cathode are wired correctly. The positive current from the batteries are going in to the long round pin on the LED, which also happens to be the small pin inside the LED. The LED may be defective, or something that is far more likely my soldering job is bad. Either way I'll take a look at it after work tomorrow.

 
Yep.
 
If you have the polarity correct, then it can only be three things:

• Bad connection due to soldering
• Damaged the LED through soldering
• LED defective

 
There is a seriously easy way to check your solder connections.  Simply place one DMM probe on the lead of the part in question, then place the other DMM probe on the lead of another part directly connected to the part in question by a wire in between.  If it measures zero resistance, then you know the wire and its solder connections are good.  If not, then you have a bad connection or short somewhere.

 

[Rainmaker91]

   
Yep.
 
If you have the polarity correct, then it can only be three things:

• Bad connection due to soldering
• Damaged the LED through soldering
• LED defective

 
There is a seriously easy way to check your solder connections.  Simply place one DMM probe on the lead of the part in question, then place the other DMM probe on the lead of another part directly connected to the part in question by a wire in between.  If it measures zero resistance, then you know the wire and its solder connections are good.  If not, then you have a bad connection or short somewhere.

It's a defective LED, I hooked up another LED and it worked straight away. I remember briefly getting light from the LED when I hooked it up directly to the 9v battery without a resistor, but even then it was difficult to get it to light up. I think it's a broken connection inside the epoxy lens, since it wanted to light up sometimes but usually not.
 
I just finished up re-soldering the LED and the pot, so hopefully the ground problems have been dealt with. If not I'll have to take a closer look at the unit circuit itself.

 

[MisterX]

Killed it by connecting it to a 9 volt battery without a current limiting resistor.

 

[Rainmaker91]

  Killed it by connecting it to a 9 volt battery without a current limiting resistor.

Might be, but it didn't work well with a resistor connected either. At any rate I still struggle getting the LED to work, so I moved the resistor to the LED cable to make it easier to swap if necessary. The bad news now is that I can't get the amp to work any more... so I'll do readings on the thing and see if I can locate the error.
 
On the plus side, I finally got a temporary case for the thing. The one I started making was way to complicated to do with what turns out to be somewhat limited skills and tools, so it's on the hiatus until I can borrow some tools and most importantly help from my grandfather.
 
Here is the current case though:
 

 

Still looks good in an old cigar box, but I really want to make a tailored one in time. 
 
Edit: figured out why it didn't work, it's the switch (It's probably the cables or my soldering that is the issue, it takes a lot to break a simple on/off switch after all). I used a jumper to test and it works fine now and all the noise is gone after re-soldering the pot. 

 

[Rainmaker91]

Got it all up and working again, swapped out the switch cables just to be sure. Either way, the LED works fine now, although this is technically the 3rd LED I tried though (killed the first two by stupidly putting it directly on 9v). Got a new short on the board though (faster ticking this time) so I'll have another look at it later, other than that it seems to work fine now
 
Also got some new better shots of it if people are curious as to how it turned out:

 

 

 

 
Thanks for all the help 

 

 

[Rainmaker91]

So... The CMoy is working brilliantly, it sounds nice and lasts for a really long time on battery power. That said, I'm having some issues with the pot. At lower sound levels it only really plays on the right channel, is this normal?

Anyway, I'm also looking at maybe doing an upgrade to my CMoy. Or perhaps rebuilding it from the bottom up. Does anyone have some pointers for a better amp design where I can use a lot of the parts that I already have? Or should I start looking at just making yet another amp from scratch (I'm thinking that I will actually start getting close in price to where I can just as well buy a decent amp). At any rate the next amp will be powered from the socket, although I'll probably look at using a pre-built PSU for it (something like a laptop charger comes to mind) and try to remove noise form the power circuit instead of messing around with high voltage circuits.