Any interest in GC input buffer and power supply regulator pcb's?

[Pedja]

It is needed some one or some ones able and ready to, once the board is finally designed, organize the fabrication and shipping.

The price of the board normally would include the fabrication costs and shipping costs with some safety margin for possible failures. The price should include also certain compensation for the time and effort invested by those who will deal with this. It would be nice if some percent could be contributed to the diyAudio site.

As long as this is the one time and only one time offer to the diyAudio community and not someone’s business, and as long as the contributors are known and recognized, I ask nothing for myself.

Pedja

[lgreen]

I've got no time to organize a group design or buy, but I wouldn't mind if you all used my design for an input buffer and regulated PS (for DIY use, not commercial use). If not it could be another starting point or point of discussion. Note- this is a low power regulated PS for the input stage only, I used chips that have a 300-500 mA rating, but which are ultra low noise. I've made a board and it works fine (with a few errors in hole sizes and jumpers becuase its a single level board) with a slight turn on and of thump that you will find happens when you regulate the input buffer as the regulators turn on and off. My buffer is actually a differential receiver for a balanced input, but an opamp buffer could be used instead. I've used trimpots so you can easily adjust the output voltage to whatever you want.

Full information on the the GC here and on my web page.

prior thread on buffer.

Schematic



Bottom of Board (that's a dime pictured).



Top of Board

[cjd]

Boredom causes people to do odd things. And I was bored this afternoon.

I've never tried to design a PCB before but found myself messing around with it this afternoon anyhow. I only got this far using Pedja's work (including PCB design) and some other posts (carlosfm) and as far as I know this could be absolute junk. I was trying to keep the reg at the edge and leave a little room to put those small caps Carlos seems so fond of, and as close to the reg as I could put them. Also room for both protection diodes.

This is just one side of course.



what needs fixin? (or, should I just not bother any more?)

C

[Pedja]

C,

I am trying to figure the orientation of the regulator… is it mounted downward or do we see the board looking from below? Besides, something like that can be done with that notice I’d rather try to avoid jumpers and I'd put current set resistor (that on pin 2) closer to the chip than diodes.

Pedja

[cjd]

Pedja: the heat sink goes off the top, and pins are marked. I think that only leaves one way for the reg to mount? I actually did this in a graphics program and started with your diagram, so it's however you had it, rotated 90 degrees clockwise.

Without going double sided or using a jumper, I was unable to get the reg at the edge of the board. It wouldn't be much to switch to a double sided layout.

As to the resistor location, that shouldn't be difficult at all. Considering I neglected to leave room for a trimpot in that spot anyhow. . .

As I said, I've never done PCB design - this stuff is only a rather new hobby of mine. So I'm a little surprised that's all you have to say.

Double sided I think cleans a few things up nicely, so may be worthwhile regardless. Since I suspect I'll be bored for some days to come, who knows. Just figured I'd not keep tweaking if the first try was a total flop.

C

[carlosfm]

Uhhh...
Yes Pedja, the reg is reversed...
And to avoid jumpers the trace that goes po pin 2 can pass behind the reg.
The PCB should have the two regs, the less boards you have to mount on the case, the better.
Anyway, it's almost copy-paste to do it.

*** EDIT***
Oh it's just one side, forget it.

[cjd]

Any better? I'm not sure if the trace to pin 3 is too thin on the one (right side), but figured I'd see if I could mirror the output placement while keeping component position the same between the two boards. Except for the two small value caps (not pictured but allowed for) it does that. The idea there was to allow these to share a heatsink (either side, or along one side) and perhaps still keep leads short. Though the output should probably be to the outside edges if this were a single PCB?



Also, I see now that I did flip the reg pins relative to Pedja's PCB design, though I do believe I got all the components to the right places despite that. So, this should be a "bottom" view of things (I dug out the spec sheet and double checked it, so I am sure to have it all wrong now).

I would NOT be able to do this stuff without reading all the posts (even the fights ) here... but PCB layout seems mostly to be a design puzzle, and that's not so far off from my areas of experience.

C

[Pedja]

Now I might sound discouraging, but I liked better the previous version.

There are a few general demands about physical organization: AC at one side, outgoing DC at the other, DC closer to the amp chips (with regulators yet positioned thus to make possible the adequate heatsinking)...

Now, about the routing on the board itself, else than it should respect the previously said things, two routes are important, and this is applicable to practically all the 3 pin adjustable devices. One is that the current set resistor path shouldn’t be shared with the output loop path or it worsens the load regulation (someone care to connect current set resistor directly to the case/tab?), and second, the sensing point goes as close as possible to the load, which in this case practically means it goes at the output of the board where it could be connected to the reservoir caps minus side. The thing I also think is not bad to practice is to mount resistors in parallel with the reg/heatsink and thus to ensure the same temperature at their ends.

Pedja

[cjd]

Originally posted by Pedja
Now I might sound discouraging, but I liked better the previous version.

Nothing discouraging at all. As long as you (or anyone) is willing to share and help me along, I'll gladly soak it up. If the result is something others can use, all the better. You've given me some things to ponder (largely to make sure I understand what you're saying).

Thanks for the feedback.

C

[troystg]

Hey C-

You mentioned

"If the result is something others can use, all the better."


Well I am watching this thread eagerly. I applaud you for giving the design a shot and being smart enough to learn from the more experienced members such as Pedja and Carlos.

Please keep up the good work and great attitude, I for one will appreciate the end results.

I love pre-made PCB's because they are SO much cleaner than p2p wiring or perf boards.

Thanks, Troy

edit: Oh yeah, thanks Pedja and Carlos for helping!!