Guide to fix up a Cmoy 2

[BlakeN 0]

I think the switched alps pot is the way I am going to go. It seems the best idea. I guess I will just have to float the pot.

[heady 0]

If you are using the switched pot, there is no need to solder the input wires to the pcb. You can solder the input wires directly to the pot and there will only be 3 wires from the pot to the pcb. With less wires floating around, it will be easier to case.

[BlakeN 0]

Thanks for the tip heady. I think I am flipfloping too much though. Somone at headfi suggested the clarostat 585 (part number 585DX4Q25F103ZP) Newark has them in stock for $2.48 and it is a drop-in replacement.

 

Might as well ask another question. The first post says you need 4 10ohm resistors but I only count 2. Am I crazy?

Edited September 27, 2006 by BlakeN

[heady 0]

Might as well ask another question. The first post says you need 4 10ohm resistors but I only count 2. Am I crazy?

 

Seems you are right. I can only find one per channel in the schematic.

 

[jasonhanjk 0]

Nope. I keyed wrongly. Just edited.

 

BTW. I got EVA in 5.1 channel but video quality cannot compare to current HDTV...

[vixr 0]

Jason, I received my boards today!!! Thank you. I finished building my first board. I hit a few snags with using electrolytic caps with a too small uF rating. I used 220uF 25v elna cerafine caps which caused a huge amount of DC offset. And caused the chips to be starved for power. They were running hot and oscillating badly. I removed the 220s and installed some 470uF caps and now everthing is ok. 1.3mV DC in the right channel and 0.7 in the left. The amp is drawing about 50 mA of current. I will use 10 AA NImH batteries @ 2000 mAh, which will give 12 volts. I should see about 40 hours of run time. I plan to use a onboard charging circuit for the batteries, with a charge time of 3 to 4 hours. A simple LM317T with a resistor and diode will be the charger. I also find that with the higher voltage rating on the electrolytic caps, the LED won't light. I will just wire it into the RK097 pot and use the default ground pad. I was planning to experiment with a TLE2426 rail splitter instead of the resistor divider. This was a great project and fun to listen to as this amp has a very clean sound. I like this design very much. I was listening with a pair of HD-555s and RCA 4GB lyra MP3. here is some pictures...

 

 

Edited October 4, 2006 by vixr

[kianannsim 0]

Hi

 

I complete my cmoy2 but I have an issue which I have no sound from the right. I troubleshooted and what I found is that the right output cable has been solder in but it does not have connectivity to the right channel so I unsoldered it and resolder in again. So this is lesson learnt for newbie and a caution for others to check.

 

But after which I found a lot of distortion to the right channel not like static but like noise (varying in amplitude) but this does not increase over how I change the volume and is present even when the volume is set to zero. Any idea what can be wrong and how do I trouble shoot.

[heady 0]

hi kianannsim, from your self diagnosis of your previous problem, it seems your soldering is a problem. Why not re-solder all the solder points (very carefully so that the components don't shift) and see if the problem goes away. This distortion is quite common symptom for cold solder joints.

 

All of us when we begin, don't solder well. It takes time to learn what makes a good solder.

 

HTH.

[BlakeN 0]

I am having the worst luck with parts LOL. I went to place my order tonight and of course the WIMA caps are out of stock so I got the 5% tollerance ones instead I hope that won't be a problem.

 

 

I was going to get these instead but went withthe 5% WIMAs instead.

 

http://www.vishay.com/docs/26032/mkt1817.pdf

 

would they have worked OK?

[kianannsim 0]

Hi Heady

 

For other than a osiloscope I will not be able to trouble shoot is it? I could do what you suggest but I think it will still help if I can find out which are the probable area of problem.

[heady 0]

Hi kianannsim, truth be told, I don't know how to use an oscilloscope. I am not EE trained. I am just sharing from my experience. The cmoy2 is quite straight forward build and problems will normally be in the wrong connection or poor soldering kind of problems.

 

When things don't work out for me, I usually take the thing apart and rebuilt again. Very drastic but I gained from the experience. I am not suggesting you do this. But re-soldering the joints will help ensure the problem is not due to poor connection.

[pegasus21 0]

The caps are used as a low pass filter in the audio signal. For the other caps, the tollerance doesn't matter.

 

The LPF will just affect the cut off frequency... I'm not too sure how many Hertz difference. Take a look at the R-C combination.

[jasonhanjk 0]

5% is ok.

 

It should be called high pass filter.

If following the spec straight, should gives around -3dB at 18Hz.

 

Ok, kianannsim.

Make sure the pot is at min.

Take the multimeter and measure the DC for left and right channel with respect to ground. What do you get?

Also can post the picture of your board, front and back?

[BlakeN 0]

Well I completed my cmoy today. I am having a small problem though. The bass is very distorted. I am guessing I have a cold solder joint somewhere so I will be going over all the solder points again. Is there anything else that could be causing this that I should look for?

 

I did use sockets for the resistors but I am pretty sure they are all seated well. I measured the resistance from the back side of the board and they are all right. The resistors I used (vishay rn60s I guess next time I will get 55s) were too big to fit in the space provided so I had to do some creative bending.

Edited October 9, 2006 by BlakeN

[jasonhanjk 0]

Jason, I received my boards today!!! Thank you. I finished building my first board. I hit a few snags with using electrolytic caps with a too small uF rating. I used 220uF 25v elna cerafine caps which caused a huge amount of DC offset. And caused the chips to be starved for power. They were running hot and oscillating badly. I removed the 220s and installed some 470uF caps and now everthing is ok. 1.3mV DC in the right channel and 0.7 in the left. The amp is drawing about 50 mA of current.

 

Sorry I missed your post. The amp shouldn't draw 50mA current. I don't see the 2 10k resistor, those are for stabilizing the virtual voltage.

 

 

 

But after which I found a lot of distortion to the right channel not like static but like noise (varying in amplitude) but this does not increase over how I change the volume and is present even when the volume is set to zero. Any idea what can be wrong and how do I trouble shoot.

 

Have you clean the PCB?