Cmoy Pcb Layout

Angel-Baby · 10th June 2005, 06:23 AM

Hello everyone I am after everyone's opinion of this cmoy layout that I redone it is the layout from guzzler over at

http://www4.head-fi.com/forums/showt...6&page=1&pp=20

I will attach the pcb file and an image if anyone can give comments of if I have made any mistakes before I go ahead and make it I will be greatly appreciated
Thanks
AB

Link for pic
http://people.aapt.net.au/grannygroover/Cmoy%20V2.jpg

dsavitsk · 10th June 2005, 06:42 AM

why don't people bypass the ps caps on these things? If it were me, I'd add a couple of film caps to do that.

motherone · 10th June 2005, 09:50 AM

I've often wondered the same thing. I usually resort to soldering my own bypasses on to the pins if needed and running cable back to a ground point.

At least on that board, the caps are close enough to the opamp that you could probably just solder some small film or ceramics to the bottom of the electrolytics.

cyteen · 10th June 2005, 02:07 PM

The cmoy layout seems to be looked down on on this forum because of the lack of bypassing on the opamp.

The prefered layout seems to be dual supplies where the positive and negative rails can be bypassed to ground using 22-100uF electrolytic capacitors. These can be bypassed with 100nF multilayer ceramic.

In addition a 100-300nF cap directly from V+ to V- pins of the op-amp with ceramic or polyester is often suggested.

Another complaint of the cmoy is the low voltage usually supplied, most opamps prefer around 15v-18v

It would be nice to see a reference layout of a head amp that was generally approved by this forum to match the suggested schematics as I for one often have problems visualizing a layout from a schematic. Also many people new to electronics start from a head amp so it might be good educationally.

tobias_svensk · 10th June 2005, 02:25 PM

I added 100nF to the rails on my SMD CMOY
Pic
Pic2

motherone · 10th June 2005, 07:00 PM

I don't look down on the Cmoy. It was the first DIY amp I built quite a few years ago. But, after learning more and more, it seems silly not to have a small set of bypasses for higher-speed opamps.

Tobias -- that is one small cmoy! Very cool.. Though I would say skip the SMD electrolytics and go with through holes for better parts selection.

Angel-Baby · 10th June 2005, 08:39 PM

Thanks everyone for the response looks like I have a few alterations up my sleve to do
Regards
AC

tobias_svensk · 11th June 2005, 12:30 AM

motherone, yea i know but that board was just to fill out the prototype board from olimex (100x160mm) so it was just for fun.
http://www.ettnet.se/~tobias/diy/panelized_low.jpg

Angel-Baby · 11th June 2005, 09:30 PM

Hello all
I redone the pcb last night and refering to the rail caps you will see where I added the 0.1 caps I think this is what your refering to please let my know what you think of the layout what needs changin or just leave it as is also I have not labled it on the board layout but just below the op amp there is 3 pads there where the TLE2426 rail splitter goes also is this realy required??.
Thanks all
AB

Link to pic http://people.aapt.net.au/grannygroover/Cmoy%20V3.jpg

guzzler · 12th June 2005, 12:12 PM

Just a quick note from me... My design does have decoupling in the form of 0805 capacitors underneath the board

g

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10th June 2005, 06:42 AM	#2
dsavitsk diyAudio Member Join Date: Jan 2005 Location: Chicago	why don't people bypass the ps caps on these things? If it were me, I'd add a couple of film caps to do that.

10th June 2005, 09:50 AM	#3
motherone diyAudio Member Join Date: Apr 2003 Location: Seattle	I've often wondered the same thing. I usually resort to soldering my own bypasses on to the pins if needed and running cable back to a ground point. At least on that board, the caps are close enough to the opamp that you could probably just solder some small film or ceramics to the bottom of the electrolytics.

10th June 2005, 02:07 PM	#4
cyteen diyAudio Member Join Date: Mar 2004 Location: S.E	The cmoy layout seems to be looked down on on this forum because of the lack of bypassing on the opamp. The prefered layout seems to be dual supplies where the positive and negative rails can be bypassed to ground using 22-100uF electrolytic capacitors. These can be bypassed with 100nF multilayer ceramic. In addition a 100-300nF cap directly from V+ to V- pins of the op-amp with ceramic or polyester is often suggested. Another complaint of the cmoy is the low voltage usually supplied, most opamps prefer around 15v-18v It would be nice to see a reference layout of a head amp that was generally approved by this forum to match the suggested schematics as I for one often have problems visualizing a layout from a schematic. Also many people new to electronics start from a head amp so it might be good educationally.

10th June 2005, 02:25 PM	#5
tobias_svensk diyAudio Member Join Date: Jan 2004 Location: Hudiksvall	I added 100nF to the rails on my SMD CMOY Pic Pic2

10th June 2005, 07:00 PM	#6
motherone diyAudio Member Join Date: Apr 2003 Location: Seattle	I don't look down on the Cmoy. It was the first DIY amp I built quite a few years ago. But, after learning more and more, it seems silly not to have a small set of bypasses for higher-speed opamps. Tobias -- that is one small cmoy! Very cool.. Though I would say skip the SMD electrolytics and go with through holes for better parts selection.

10th June 2005, 08:39 PM	#7
Angel-Baby diyAudio Member Join Date: Jan 2004 Location: Victoria	Thanks everyone for the response looks like I have a few alterations up my sleve to do Regards AC

11th June 2005, 12:30 AM	#8
tobias_svensk diyAudio Member Join Date: Jan 2004 Location: Hudiksvall	motherone, yea i know but that board was just to fill out the prototype board from olimex (100x160mm) so it was just for fun. http://www.ettnet.se/~tobias/diy/panelized_low.jpg

11th June 2005, 09:30 PM	#9
Angel-Baby diyAudio Member Join Date: Jan 2004 Location: Victoria	Hello all I redone the pcb last night and refering to the rail caps you will see where I added the 0.1 caps I think this is what your refering to please let my know what you think of the layout what needs changin or just leave it as is also I have not labled it on the board layout but just below the op amp there is 3 pads there where the TLE2426 rail splitter goes also is this realy required??. Thanks all AB Link to pic http://people.aapt.net.au/grannygroover/Cmoy%20V3.jpg

12th June 2005, 12:12 PM	#10
guzzler diyAudio Member Join Date: Feb 2003 Location: Scotland	Just a quick note from me... My design does have decoupling in the form of 0805 capacitors underneath the board g