Cmoy Pcb Layout

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cyteen

Member
2004-03-31 12:06 pm
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.
 
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.
 
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 V3.jpg
 
I can make you a board if you don't mind the home etched brew. What do you want, a small portable SOIC board or one that can fit DIPs for home use?

Here are some pics of a pair of "mono block" boards I made.

http://i15.tinypic.com/2z3zbxv.jpg
http://i17.tinypic.com/2rwawqd.jpg


They have OPA551 installed so they can handle a supply of +-30v and output 200ma. That should be able to drive any pair of phones (except for the one of a kind 6.6R variety:mad: )

Input impedance is 20k, input caps are 4.4uf ceramics (I have no prob with ceramics as input caps), supply caps are 100uf Panasonic NHG bypassed by 0.1uf ceramics, and the gain is adjustable with a 10k pot.
 
how much?, and can you make it like this:

[IMGDEAD]http://tinypic.com/2af4vb[/IMGDEAD]
[IMGDEAD]http://tinypic.com/2af4t5[/IMGDEAD]

Omitting the rail splitter and using the pad layout for an Alps RK097. Now that I think of it, it is the exact one at the first post of this thread:

[IMGDEAD]http://people.aapt.net.au/grannygroover/Cmoy%20V2.jpg[/IMGDEAD]
 
So you want a DIP version for a dual opamp like OPA2134? I guess I could make one up from scratch. I was more hoping you would be OK with one of the boards I have already made, dual or single SMD or single DIP. I would be wiling to send you one of those options for nothing more than shipping cost.

If you want the board exactly like the board from the first page; I can probably make it. I think the file uses Protel, which I don't have, so I will have to get it first.

EDIT: I have the file open in Protel DXP. Give me some time to figure this program out. It looks like it's gonna be a long night.:xeye:
 
Man, this Protel is a nightmare. I need to print out the layout like the pic below, but it doesn't want to play nice.

I don't think I have the patience to mess with this program as I will probably never use it for anything again. If you can manage to print me out a black positive of the traces and silk layer I can have this board made in a day. I use PrimoPdf to print to pdf files.

http://i18.tinypic.com/313hctw.jpg
 
I make my own C'Moy PCB design for my own needs. PCB include onboard input and output jacks, ALPS pot with switch, TLE2426 rail splitter and dual opamp. El caps is as close as posible to opamp power legs, feedback loop is phisicaly as short as posible.
Thanks to minimal posible PCB order , I have 15 or more boards owerstock. Boards shud be here next week, so if eny one have interest, notify me.
Zigis.
 

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