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CK2III questions

post #1 of 10
Thread Starter 

I'm currently putting together a CK2III using all the recommended parts. I'm nearly done but I do have a few questions. I've put together a cmoy before so I do have some experience but I am in no way experienced at diy electronics. 

 

1. Me being smart, decided to see what color the led was by hooking it up to a 9v battery which immediately blew out the led. Is an led mandatory? or can it just be bridged with a lead? Also, I can't find any information on the orientation of the led on the board. Which way should the led be hooked up to the board?

 

2. I've hooked up the primary leads of the transformers but the secondary leads are giving me a bit of trouble. As of now, I have the wire with the voltage through it going to the positive or square pad on the board. Is that correct?

 

Sorry if the wording is a bit confusing, I can take pictures later if it would help. Thanks

post #2 of 10

1) You need a resistor to drop current to prevent LEDs from exploding ;)   LED is not mandatory, do not bridge the lead, simply don't populate it.  LEDs are directional, the longer lead is the anode and should be connected to V+.

2) Transformers output AC voltage, there is no + or - with AC (it constantly alternates).  Connect each pair of secondaries to different pads (if your wires are 2x red and 2x brown, measure AC to make sure you get the correct voltage between each red/brown pair and connect each pair to the pads on the board).  The key here is to measure AC voltage with your DMM to make sure you get 15V across each secondary before you solder them to the board.

post #3 of 10
Thread Starter 

I think I'm an idiot, I can't find any indication of which lead is positive and which is negative on the board.

post #4 of 10

I don't recall there being an indicator.

 

R40 just below it is the current limiter, so I would guess the hole closest to it is the positive hole...  I had mine on a header and had to flip it.

 

Looking at the traces the -15v seems to go to the top hole, so pretty sure it is negative top, positive bottom.

post #5 of 10
Thread Starter 

So I've put everything together now and everything works except for one small thing. I'm getting a buzz with the output. I know this is normally a grounding issue or a issue with interference from the toroid but the weird thing is, when i have the volume on minimum, the buzz is on the right side of the headphones but as I turn up the volume, the buzz increases and shifts to the left side of the headphones. 

post #6 of 10

 

Sounds odd.

 

Try the normal things:

 

Rotate the transformer.

 

Check the grounding, including the pot. 

 

If nothing else works you might need a ground loop breaker.

post #7 of 10

1) Short the inputs to ground, does it still exist?

2) Remove the signal wires from the pot (de-solder, unhook, whatever).  Does the buzzing still exist?

 

I'm trying to determine if the buzzing is from the amp or wiring.

 

Do what peppe suggested as well.  The best thing is to pull the transformer out of the case and see if the buzzing remains.

 

Pictures might help.

post #8 of 10

I agree, might be nice to see some pictures at this point. 

 

Are you following the build instructions out on AMB audio?  If not, go here -> http://www.amb.org/audio/ck2/

 

Other things to look for:

 

Cold solder joints. 

Connections for the volume pot as well as the output jack. 

What does your offset look like?

 

Good luck!

post #9 of 10
Thread Starter 

Rotating the transformer worked. Thanks for all the help. I'm not quite sure why though. Could someone explain it to me just for the intellectual value?

post #10 of 10

 

Quote:
Originally Posted by CookieCutter View Post

Rotating the transformer worked. Thanks for all the help. I'm not quite sure why though. Could someone explain it to me just for the intellectual value?


Tranasformers have what is called "leakage flux" this is is magnetic flux that gets out of the transformer. Think of it as a directional nosie source - if you aim it correctly the noise goes away. 

 

Toroidal transformers are kind of tricky with leakage flux - under ideal conditions they have much less than EI (traditional boxxy looking transformers) BUT the leakage flux is not as predictable. With an EI transformer you can easily say "dont put something here" OR "aim the transformer this way from day 1" to avoid noise. The solution of keeping the toroidal transformer as far from sensative stuff, and rotating it is the best way with them.

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