[tyre]

Tiny cmoy pcb. It's probably too small to solder by hand though. Overall dimensions are .675" x .620" (17.15mm x 15.75mm) or about the size of a dime.

MSOP opamp
0603 resistors
0805 input capacitors
5mm power supply capacitors
tle2426
10mil traces

 

[guzzler]

Lovely stuff... Easy (well, a little tricky) to solder, just need some small soldering wire and good tweezers. You could get rid of the input coupling caps, as the only common ones are ceramic which aren't nice in the audio path. You could use PPS, but that's awfully pricey and probably unecessary anyway. Look forward to seeing it "in the flesh"

g

 

[nikongod]

any thought on making it accept bipolar chips?

use the 2 input caps for the "small psu caps" instead of input caps.

 

[tyre]

Quote:

Originally Posted by guzzler Lovely stuff... Easy (well, a little tricky) to solder, just need some small soldering wire and good tweezers.

Yay, someone actually likes my tiny cmoy.

Quote:

You could get rid of the input coupling caps, as the only common ones are ceramic which aren't nice in the audio path.

I used the 0805 input capacitors after looking through the Digikey catalog and noticing the Panasonic ECP-U series. They come in pretty small package sizes. I would probably use the 25V .15uF ones at $.33 each. It looks like they are "plastic film" caps. I'd guess that means they are somewhere below PPS and PEN film quality wise.

I can get rid of them if neccessary though.

Quote:

Look forward to seeing it "in the flesh"

I'm pretty much broke at the moment so they probably won't get made any time soon.

I was thinking of eventually trying Olimex since they're cheap and allow panelization, but I read somewhere that they aren't very good with small traces.

Quote:

Originally Posted by nikongod any thought on making it accept bipolar chips?

I don't know of any bipolar smd capacitors. Which brand/series were you refering to? Also, what would be the advantage of bipolars over electrolytics?

 

[tobias_svensk]

Quote:

Originally Posted by tyre I was thinking of eventually trying Olimex since they're cheap and allow panelization, but I read somewhere that they aren't very good with small traces.

I recently ordered from Olimex, they panelized 1 preamp, 2 lm3886, 2 preamp psu and 2 SMD cmoys for me on a 160x100mm 2-layer board.

On the cmoy I have 16 mil as smallest trace and it seems to be all good here, the only thing Olimex seems not to be so good in is that the drillholes can be a little bit offset on the pads. Maybe you could make the traces 16-20mil?
http://www.ettnet.se/~tobias/diy/cmoy/cmoy_smd_top.jpg
http://www.ettnet.se/~tobias/diy/cmoy.png

 

[tyre]

pcb from sparkfun.com

 

[tyre]

Here's the finished amp. It was actually not as dificult to solder as I thought it would be. And the amp works surprisingly well considering the weak output current capability of the particular opamp I used. It sounds like every other cmoy I've made.

I ended up changing the layout slightly to include ceramic power supply bypass capacitors on the underside of the board and a smd diode to protect against reverse polarity if used as a portable.

 

[cire]

wow thats very impressive.

just curious, why did you choose that amp chip? whats the input voltage?

 

[tyre]

Quote:

wow thats very impressive. just curious, why did you choose that amp chip? whats the input voltage?

The opamp is an AD8698 and I used it because that's what I had on hand. Ideally though, I would use the msop versions of either the AD8066 or AD822, the former having higher output current and the latter has low quiescent current for battery use.

I'm currently running it off an diy LM317 power supply set to 12V. The voltage isn't limited by the opamp though, it's the small 6.3V 220uF power supply capacitors.

 

[cire]

any chance i can get a board?

 

[tyre]

Quote:

any chance i can get a board?

Ok, I have one extra pcb if you want it. Just to remind you though, It's pretty tedious to solder all the parts on. A very small soldering iron tip is best.

hopefully it's still allowed on head-fi to sell a pcb at cost

 

[Nisbeth]

Quote:

Originally Posted by tobias_svensk the only thing Olimex seems not to be so good in is that the drillholes can be a little bit offset on the pads.

Sorry for the thread hijack, but that's probably because you have measurements in imperial units and Olimex uses metric (or vice versa). IIRC, there's something on their website-FAQ about this

/U.

 

[tyre]

Okay, here's the schematic and pic of the board layout. I ended up just removing the part numbers from the layout. The text is too small to be printed correctly. I made the board a little smaller with the extra room.

I'm working up a part list that I'll add later.

 

[tyre]

.

 

[Andrea]

This is the kind of circumstance when you'd say "small is beautiful" ! Congrats