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goering 24th August 2004 03:53 AM

Need comments on this P3A PCB layout

First off, having read some of the threads about ripping off copyrighted PCB designs, please rest assured that I did this PCB by myself using protel demo. Actually, I already bought a PCB from Rod and will probably buy a real P3A as I will need Rod's expert guidance while building the amp.

Nonetheless, since I really want to learn how to design my own PCBs eventually, it would help a lot if I can get your comments on what is wrong with this attempt of mine. I'm just using P3A as an example because I know many are familiar with it and it's not too complicated.

I used MJ2955 and 2N3055 as output transistors and will mount them on a heatsink and connect them directly with wires instead of copper traces.

Thanks for the help.

goering 24th August 2004 05:18 AM

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Oops, it seems settings aren't saved when you preview posts... here's the pic...

destroyer X 25th August 2004 05:34 AM

Putting a schematic scratch, and avoiding the brand title
Will be easier to help....

I was trying to see the possibility of output to input coupling...common when zobel filter is near the input.... also output magnetic field....i could not because no schematic at hand.

Of course i can find the schematic, but will be more easy to us, if already in place to use.

If you avoid the P3A name, we can be out of copyrigth problems, this way, when you put the brand on it...people will run of you to avoid problems.

I think those copyrigth.....hummmm....those rules....hummmmm...but i do not make laws, i am forced to obbey them too, despite of have not empathy, do not like those problems related "objections" related our complete freedom.

I can understand, obviously the reasons or protect this or that....but our new world, with magnificent comunications.... this will be no use...because people can do those things directly... and in silence....without make noise, copies are going everywhere.

Someone will appear and will say...bad man you are....this is no good.....

But i thank you the wonderfull work you done, good man you are....but the title is the problem....try to erase the P3A, call moderators they can do that if you inform the thread number clicking rigth in mouse over thread image....inform them the number...they can erase all...or maybe allowed you to edit and substitute P3A for "this circuit"

Also cannot reproduce the schematic...but if you put it in one simulator program, or make a hand scratch with a pen....not telling the will avoid problems too.

Forum people, normally, jump those threads.... to avoid some partnership related be against copyrigth my own idea, as a Brazilian.... too much free i something that i do not like....but have to obbey to avoid people felling bad against me.

My intention, i ensure you, is to be helpfull.

You may do what your conscience will tell you.



jaycee 25th August 2004 03:42 PM

To me, the layout looks overcomplicated. You can get a P3A onto a single sided PCB if you try hard enough. I would look at some more PCB layouts for other amplifiers, note how they are arranged, and follow accordingly.

I won't elaborate further because most people here get very annoyed at people asking for help making their own PCB's for Rod's designs, as he sells them and makes a living from them. I made my own merely because I wanted the experience of creating a PCB.

destroyer X 25th August 2004 04:57 PM

I think board are very easy to be made
I reduce the schematic image.... then i put over the board... with a fine steel point and a hammer i put marks on the copper....and them, with a pen i draw circles over the dots i made..... this way, loocking into the board i trace the lines with those standard marker pencils...Sanford or something alike.... goes to acid.... and ready!..... i do not worry if pretty or not..... i will hear sound...not show the boards!... they will be inside the not mind about them..... other thing... i always put components in solder side.... easy to check.... doing that more than 40 years this way.... and tried the other way.... i am sorry...but i think mine is easier and faster.


goering 27th August 2004 04:40 AM

Carlos and Jaycee,

Thanks for the kind replies. I understand your hesitation and am grateful for your intent to help. Although I don't intend to take Rod's business away (it's obvious I can't even draw a decent pcb :D ) Anyway, I did intend to buy a pcb from Rod, and I'll see the how he did it won't I? Just needed some useful tips for future use. Thanks...

sam9 27th August 2004 05:11 AM

If you want to try something that may be an improvement, thus mooting the rip-off arguments and further relieving your concience, arrange the VBE multiplyer so it can be mounted on the sink very close to one of the output devices. Should keep the bias closer to optimum as the operating temp changes.

Previous comments about keeping output circuits such as the zobel far, far away from the input is good advice. I had to learn this for myself. Very irritating experience.

Maybe use wider tracks to reduce impedances.

Just my thoughts

destroyer X 27th August 2004 06:04 AM

That's rigth, make all things simple
Not only because simple is normally better, but also because it is easier.

Less parts, less acumulated distortions, less money, less work and many times nicer sound.

those simple things normally can be extend to life, simple woman, simple car, simple work, everything simple can reduce problems.

Just follow the schematic.... the things in the rigth side , keep them rigth side, also up an down and left.

I used to solder copper side, i do not create holes in boards, and also i can glue the board easy, and also easy to remove, no isolations, screws and all stuff. Yes, this way is ugly, i agreed.

The problem when doing those simple boards is that will never return to standard ones.

You will see that the schematic is there, you can also paint the schematic there, so, to check if done correctly is easy, do not need to turn the board and understand that the emitter, now, is not anymore it is down....really more complicated.

Our own life, by itself, create some problems that turn the life sometimes difficult, why create more problems when you can simplify?

That's something related "philosophy", and i now each person thinks different.... that's our worst problem on earth..... hehe.... damn confusion.


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