[CingKrab]

I've laid out a CMOY PCB that's kind of MINT style -- to be mounted vertically in an Altoids tin. It's 20mm x 50 mm. Does anyone know if that's too tall to fit in the Altoids tin? I've printed it out and fiddled with it and it definitely seems tight. I would also appreciate any feedback on the layout itself, as I'm inexperienced at this.

 

[NeilR]

I just measured an Altoids tin. It is 20mm high, MEASURED FROM THE OUTSIDE OF THE CASE. You could end up a mm or two oversized....

You need to get your Atloids tin, then print the board out and cut up the paper to play with the fit.

Just an idea here- it seems to me that the objective should be to get two 9V batteries in the case. If I were doing this, I would make the board run across the short side of the case and put the pot in the middle of the board, with PCB mounted jacks like the Switchcrafts. The corners of the board would have to be left empty and rounded to fit the case.

 

[xluben]

Quote:

Originally Posted by NeilR Just an idea here- it seems to me that the objective should be to get two 9V batteries in the case. If I were doing this, I would make the board run across the short side of the case and put the pot in the middle of the board, with PCB mounted jacks like the Switchcrafts. The corners of the board would have to be left empty and rounded to fit the case.

Here's an example of that:

From this thread (near the bottom):

http://www6.head-fi.org/forums/showthread.php?t=138614

 

[NeilR]

Yup, something like that. I did a very similar layout on perf board. I used 470uf Panasonic FM caps and I wanted to fit a browndog (double dip8) to use OPA627s, in some sort of maxed out version. I left off the input caps. I found that it was so tight that the batteries were pushing the caps back into the browndog adapter, giving it a lean:

http://www.pbase.com/nrothschild/cmoy_2

Even without the browndogs, it was proibably a bit too tight unless I used different battery straps with a thinner top.

If I were doing this with SMD, that would preclude the browndogs, of course. I would want lots of space to max out the PSU caps and especially the input caps. To do that I would take the board edge to edge.

Just BSing about my own musings.... if I were going to seriously do an SMD board for a tin, I would do a Mint style, with buffers that accomodated the ALPS97 between the jacks on the end panel. I don't like the volume control on the long side panel and I don't like the idea of an extra switch for power. That would be my perfect mint tin amp, especially if I could fit in a cross feed (yea right!)

Regards,
Neil

 

[CingKrab]

Quote:

Originally Posted by NeilR Yup, something like that. I did a very similar layout on perf board. I used 470uf Panasonic FM caps and I wanted to fit a browndog (double dip8) to use OPA627s, in some sort of maxed out version. I left off the input caps. I found that it was so tight that the batteries were pushing the caps back into the browndog adapter, giving it a lean: http://www.pbase.com/nrothschild/cmoy_2 Even without the browndogs, it was proibably a bit too tight unless I used different battery straps with a thinner top. If I were doing this with SMD, that would preclude the browndogs, of course. I would want lots of space to max out the PSU caps and especially the input caps. To do that I would take the board edge to edge. Just BSing about my own musings.... if I were going to seriously do an SMD board for a tin, I would do a Mint style, with buffers that accomodated the ALPS97 between the jacks on the end panel. I don't like the volume control on the long side panel and I don't like the idea of an extra switch for power. That would be my perfect mint tin amp, especially if I could fit in a cross feed (yea right!) Regards, Neil

Yeah, this is why I chose to do it MINT style in SMD -- to maximize the space for the input and PSU caps. The Panasonic FM 470uF 10mm spacing caps are 16 mm tall, and I'm using a crowbar diode that is ~3.2mm placed on the reverse side, which brings me to almost 20mm originally with a horizontally placed board. I guess I'd have to reduce the width of the input caps -- the 1.2uF ones with 15mm spacing that I want to use are too wide to accomodate both the Alps pot and two of them vertically, which is why I made the board 20 mm tall. I think I'll give the horizontally mounted version another shot and see if I could place the diode on the top side.

 

[NeilR]

You can make the board 32x52 and still fit two batteries, with nice battery straps. You could actually go 34mm, I think, as long as nothing is sticking out of that end. That is based on a Cmoy I have where I had to file down some of the battery strap, which is why 32mm or so would be better (to avoid that).

You would have to center the pot (where it belongs!) and add the jacks to the board, and allow for rounding the edges on the outside of the jacks where they meet the corners of the tin.

You could put your crowbar vertical, standing on end.

Then I would buy one or two

 

[CingKrab]

Well, I finally finished up this board, with board mounted jacks. It's 37mm x 36mm, which should fit into the Altoids tin with 2 9V batteries and with no corner rounding. Does anyone see any problems with the layout?

 

[NeilR]

Personally I think it is better to round the corners and get the jacks further from the volume knob. I think you will find that even with tiny input and output plugs that it is a tight fit. In my Cmoy, the outside edges of the jacks are 42-43mm apart and that worked out well for me. If you make the board that size there is very little rounding needed.

My batteries (2x9v 200maH Maha) sit 36mm from the jack side edge of the tin. That was after I rounded the corner off of one battery clip. the exact amount of space you need is dependent on the batteries and clips you use. I think you should take it down to 32-33mm if you can. My 36mm measurement assumes that the board will be flush up against the jack side edge, which may not work out after you mount the jacks. What I am saying here is that i think your layout could put you one or two mm short. Since your caps sit almost at the edge of the board, you may end up stressing the caps and the related foil pads. A few mm of breathing room will make things go smoother. The same thing happened to me when i built a perfboard version- I was 1-2mm too tight and it is a nuisance.

I have no comment about the electrical layout- I have some day job issues going on now.

good luck!

 

[CingKrab]

I've widened the board to 42mm, but I had to leave it at 36mm length -- I don't think I can shorten it. Blueworm in the thread linked above had a board with similar dimensions that fit a Penguin tin with two 9V batteries, so I think it should work. I've flipped the opamp to the bottom of the board so I can take out the four vias on the -ve input and the output, but I'm having problems with the DRC if I put a rectangle on the restrict layer to keep out the ground plane near the opamp (well, I guess it's supposed to do that). Would the top or bottom be a better location for the opamp?

 

[NeilR]

I recall a discussion here about those Ricola tins and that tin is larger than a USA mint tin. I thought it was the thread you refer to but i don't see the sizing; may have been another thread. Blueworm is in Europe; his tins may not be exactly the same size. Good luck! Can't help you with the fine points of your chip placement.

 

[Pars]

I personally prefer the opamps on the top, but thats just bias I guess. Your decoupling caps need to be right on the opamp V+/V- pins, or as close as you can get to it. If you run the ground plane right down the middle of the chip, you should be able to run the caps lengthwise very close to the pins. DRC will bitch about the restrict layer... as far as I know just ignore that. If you do an export of the board top/bottom to a graphic, it doesn't seem to bother anything.

 

[blueworm]

Quote:

Originally Posted by NeilR I recall a discussion here about those Ricola tins and that tin is larger than a USA mint tin. I thought it was the thread you refer to but i don't see the sizing; may have been another thread. Blueworm is in Europe; his tins may not be exactly the same size. Good luck! Can't help you with the fine points of your chip placement.

I can confirm ricola tins are exactly the same size as U.S.A purchased penguin mint tins. Not sure about altoid mint tins.

If you want to see small cmos check out this site.
Sijosae is the micro moy king.
Bare in mind the pot is optional!

 

[NeilR]

The OUTSIDE dimensions of my Altoids tin is 58.7 x 93.6mm. i measured the outside dimension because it is ieasier with electronic calipers. Compare to your Penguin and Ricola tins.

 

[CingKrab]

Pars, here are my decoupling caps:



Are these close enough? I have 10uF tantalums as well, but they are farther away (under the rail electrolytics)

Oops, nevermind about the DRC errors -- it was due to low isolate value.

 

[MagusG]

We need a Cha-47 board that allows room for two 9V batteries in a mint tin.
-Mag