| dsavitsk |
| 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. |
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| motherone |
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. |
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| cyteen |
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. |
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| tobias_svensk |
I added 100nF to the rails on my SMD CMOY
Pic
Pic2 |
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| motherone |
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. |
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| Angel-Baby |
Thanks everyone for the response looks like I have a few alterations up my sleve to do
Regards
AC |
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| Angel-Baby |
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 |
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| guzzler |
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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| colonelkernel8 |
| Is there anywhere at all I can buy a simple Cmoy PCB? Just the basic design. Thats all I need. I have looked for WEEKS and yet I cannot find a single group buy, provider, store, anything that has a Cmoy board that I can buy. |
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| theAnonymous1 |
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. |
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| colonelkernel8 |
how much?, and can you make it like this:
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:
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| theAnonymous1 |
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: |
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| theAnonymous1 |
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 |
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| gmilitano |
Following the CMoy Tutorial I pulled togther the PCB in less than 1/2 hour using the Radio Shack Proto board. Here is my CMoy Headphone Amplifier.
While it is not as clean as a printed PCB, I suggest you try the proto board approach as it will give you insight on how to use the board for other projects. |
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| colonelkernel8 |
| I know how to use a protoboard (this is not my first DIY). My purpose for having a clean pcb because this cmoy is being given as a gift. I will get the trace silhouette for you Anonymous1. |
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| Zigis |
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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| Zigis |
| Boards size is 4 x 5 cm , silcscreen, solder mask. |
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| colonelkernel8 |
Im game. E-mail me bro.
colonelkernel8 <at> comcast <dot> net
Thanks.
This is based on tangent's design right? So the part identifications are the same?
Are those caps the right size? They seem small compared to the rest of the components.
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| colonelkernel8 |
Actually, I think I will have Anonymous1 make me one. Here is the traces in pdf form:
If you make it, first give me a quote on the cost, and then be sure to do a really nice job, ok? Like cut the board nice and square.
Thanks man. |
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| theAnonymous1 |
colonel,
I'll do my best on the board, but if your looking for picture perfect results you might want to get a backup plan. Don't get me wrong, it won't look like a complete hack job, but it won't look like a professionally made board either.
You can't beat the price though. It will only cost you a bit of patience. |
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| colonelkernel8 |
| Oh, I know. My expectations are reasonable. I will not likely be disappointed. |
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| Zigis |
This is basic cmoy design with TLE2426 rail splitter ,described by Tangent.
ALPS pot with switch I bay from Tangent.
I attach my common schematic , probable components name differ from CMoy- Tangent. Attached sch. I use for my PCB.
Original CMoy use input C - 0.1mf, R - 100 k
There is 2 way to increase lower frequency with similar result :
1. Same input R, incresed C (incresed size and price too)
2. Same input C, incresed R
I prefere second way, I use input R - 1M , not 100k
Zigis
P.S. I send sch. tomorrow and mail too |
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| colonelkernel8 |
| Zigi, don't worry about it. I am going to get one from Anonymous. |
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| theAnonymous1 |
Hey colonel, just an update on things.
I have the positive printed out and I'm getting ready to do the etching. I just happened to have a strip of PCB with the correct width, so I will only have to ghetto cut one side. I will post some pics for your approval when I am done.
Did you want me to drill the holes? I don't have a drill press so I have to free hand it with a dremel. I can get the holes pretty centered, but if you have a press you might want to do it yourself. |
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| colonelkernel8 |
| No, I do not have easy access to a press. Feel free to drill the holes. (I can drill the 4 mounting holes, so don't worry about that. |
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| theAnonymous1 |
| Almost done drilling. Do you want me to solder in a DIP socket, I have a few extra? |
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| colonelkernel8 |
| Yeah, sure, save me the trouble of ordering one. Thanks bud. |
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| theAnonymous1 |
OK, done. I was going to give you two boards but I miffed one up when I was drilling. I really need to get a press and new bits. Here are a couple pics.
If it's satisfactory, drop me a mail with your address and I'll get it sent out in the morning. |
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| colonelkernel8 |
| thats fantastic, thanks a lot man. |
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| colonelkernel8 |
Did you get my e-mail? If not, e-mail me and I'll reply with my address.
colonelkernel8 <at> comcast <dot> net |
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