[Chet_Summers]

 

[size=medium] Basically all I want is to amp the headphone output because I don't want to bother with a line-out dock connector.  I have some old Cmoy and Mint amps I made using a Pac-Tec enclosure and was trying to figure out how to make it as small as possible while still using a 9V battery for power.  I got rid of the volume knob and just used the source for volume control, so I then soldered the input cable directly to the board (1/8" male jack) instead of mounting 1/8" female jacks on the enclosure.  The on/off display LED also got the cut.
 



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I used the same Hammond enclosure as the AMB Mini^3 since it seemed the smallest one that could still hold a 9V, but still ran out of room.  Had to move the caps for the input RC low-pass filter off the board as seen in the photo.  The result is a not-very-rugged mess of heat-shrink tubing and zip ties.

The end product sounds fine, and it's more portable and less of a hassle than my other amps, but there's definitely room for improvement.  Here's what I don't like about it:
- It's about 4 times bigger than I want it to be. What I really want is a higher quality Boosteroo, but the FiiO E3 and E5 don't seem to fit the bill (plus it's more fun to DIY).
- The paddle switch on the front is too big. I avoided the silver mini-toggle because I was going for a look that was less homemade, not sure if I succeeded. A mini slide switch would be ideal, but I don't know how to drill square holes and all the panel mount ones looked too big.
- I'd love for this to use a rechargeable 9V or something smaller.  The CMoy schematic is dead simple, but I'm not sure if I'd have to switch op amps (and sacrifice sound quality) if I drop the voltage and current with a smaller rechargeable battery cell.
 
Any ideas/feedback would be much appreciated.  
 
Many thanks to Tangent for the website with part numbers and assembly instructions, great for reference!

 

[Reintz]

If you want to fit the input and output jacks, volume control, switch and led, I'd suggest you to etch your own PCB. Perfboard takes too much space.
I built my CMoy in the same enclosure.




 
It runs on a 9volt rechargeable. I made the square hole for the switch buy first drilling two round holes side-by-side and then filing them to fit the switch.

 

[BlackbeardBen]

Now that is a good looking CMoy...

 

[Chet_Summers]

Nice Reintz!  Looks like you have the same problem I do in that when the 9V runs out of juice you have to unscrew the back panel to swap batteries and/or recharge. What I was thinking would be nice would be to have the charger in the enclosure and then just have a DC jack on the back, like the Mini^3.  I just don't know what the circuit is for that.

 

[sprocket87]

Tangent has a basic schematic for a NiMH trickle charger on his Pimeta page. Basically you just need a diode or two plus a resistor and an LM317 voltage regulator. It's not intelligent (dumb straight trickle charge only, you have to match your charging voltage and resistor value to the battery you use) but its compact and simple.

 

[Fred_fred2004]

This is the best thread I know of for a simple trickle charger
 
http://www.head-fi.org/forum/thread/185377/trickle-chargers
 
cheers
FRED

 

[JamesMcProgger]

anyone care to tell what is the part number of that enclosure at PacTec? or a link

 

[Chet_Summers]

The enclosures in the pictures above are Hammond 1455C801BK, Mouser part number 546-1455C801BK (for black). 
The old PacTec enclosure I used was an HML-9VB, but it's not as nice as the Hammond.
 
Has anyone tried a CMoy with something lower than a 9V for the power supply (op amp would then run at something less than +/- 4.5V)?

 

[tangent]

Quote:

 
I avoided the silver mini-toggle because I was going for a look that was less homemade, not sure if I succeeded. A mini slide switch would be ideal, but I don't know how to drill square holes and all the panel mount ones looked too big.

 
Some lines of toggle switches have vinyl bat covers you can buy that might help with the look. ("Hats for bats. Keep bats warm. Gracias.")
 
Or, I've seen round-hole mounted latching pushbutton switches small enough to fit your application. The panel-mount ones tend to have short actions and so would be easier to bump off accidentally. You could board-mount one with a longer action so that only enough of the actuator button stuck through the panel as needed to toggle it, but then you have a problem precisely aligning the button and the hole in the panel.
 
Maybe it's time for you to make your first professional panel? It'll easily double your parts cost on this project, but if you want a professional look...
 
Quote:

Many thanks to Tangent for the website with part numbers and assembly instructions, great for reference!

 
 
Welcome.
 
Quote:

That's a very nice layout, Reintz! I'd round off some of those 90 degree bends with 45s, but.. The main thing I like is the "flow" of the traces that gives at least the illusion that it doesn't have any top-side jumpers. Maybe to meet both goals, you could do a 1970's style hand layout, with no hard bends at all.
 
 
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Gorgeous construction, too!
 
Maybe you could offer Chet some tips on how you got those headphone jacks to align with the panel holes? Professional panels are one way, but I'm guessing you did this by hand.
 
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anyone care to tell what is the part number of that enclosure at PacTec? or a link

It's not a PacTec. The Mini³ enclosure is a Hammond 1455C801. (Or '802 for plastic panels.)

 

[tangent]

Quote:

Has anyone tried a CMoy with something lower than a 9V for the power supply (op amp would then run at something less than +/- 4.5V)?

Yes, you can make a CMoy variant that runs on less voltage, but you have to at least replace the resistor divider in the power supply with a TLE2426 (or equivalent) to deal with the voltage imbalance problem.
 
You also want to switch to a more efficient op-amp. For a line voltage application like this, the AD823 might suit. Some of the 12V-max LMmumble ones you see discussed a lot here might also work.
 
The real trick, though, is finding a battery with less than 9V that also has enough power output and is actually more compact. See my post in this other thread for an example of an alternative that won't work.

 

[JamesMcProgger]

Thank you both.
 
looks sweet in black. looks like the same of mi mini3, which i bought, not made.

 

[Reintz]

 
Quote:

Nice Reintz!  Looks like you have the same problem I do in that when the 9V runs out of juice you have to unscrew the back panel to swap batteries and/or recharge. What I was thinking would be nice would be to have the charger in the enclosure and then just have a DC jack on the back, like the Mini^3.  I just don't know what the circuit is for that.

 
I did consider a charging circuit, but I just don't have any space for a DC jack. I would need one of those small Alps pots with a built-in power switch, but I haven't found a local source for those. Instead I'm building a low battery indicator based on the circuit found here http://www.head-fi.org/forum/thread/82115/low-battery-indicator-circuits/45 I managed to resize Avro_Arrow's layout to 0.625"x0.625" and I'm planning to fit it inside the CMoy.
 

 
Quote:

Has anyone tried a CMoy with something lower than a 9V for the power supply (op amp would then run at something less than +/- 4.5V)?

 
I built one that runs of 5V (USB power). You can find it here http://www.head-fi.org/forum/thread/525557/cmoy-in-a-zippo-lighter
 
 
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That's a very nice layout, Reintz! I'd round off some of those 90 degree bends with 45s, but.. The main thing I like is the "flow" of the traces that gives at least the illusion that it doesn't have any top-side jumpers. Maybe to meet both goals, you could do a 1970's style hand layout, with no hard bends at all.

 
Thanks! It means alot as your tutorial led me to the whole DIY thing.
 
Yes, there are no top-side jumpers. The top looks like this

By now I have replaced the TO-92 tle2426 with a SO-8. Inspired by your Adaptle. This was also my very first SMD.

I like idea of those "flow" traces but I doubt I have a good enough drawing hand for that. I know I can make it work, but I'm just not sure I will be satisfied with the looks. Is there any PCB software for that?
 
 
 
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Maybe you could offer Chet some tips on how you got those headphone jacks to align with the panel holes? Professional panels are one way, but I'm guessing you did this by hand.

 
First I made a hole for the potentiometer shaft. With the finished PCB in the enclosure, I measured the distances between the shaft and two sides of the enclosure. Marked the spot on the panel and drilled it. It's not a big thing if this hole isn't perfect as it's covered by the spacer and nut. For the jack holes, I screwed the front panel on, put a little acrylic paint onto the front sides of the jacks and slided the PCB in from the back of the enclosure. When pressed against the front panel, the jacks left two circles onto it (from the acrylic). I then drilled it with a small drillbit, then checked the alignment. Then drilled it with a a bit bigger drill and checked again. As the holes are a bit off they will clear the jacks from one side before the other. At that point I took a small round file and filed the hole to align with the jack. 

 

[tangent]

 
 
Quote:

I doubt I have a good enough drawing hand for that.

 
If I were to do such a thing, I'd start with a bitmap of the angular CAD art, pull that into a vector illustration program (Adobe Illustrator, Corel Draw, Inkscape...), put it on a semitransparent, locked layer, and trace it on a layer above it.
 
By keeping the original CAD file as a layer for reference, you ensure you have the trace end points in the right places — they still have to line up with the components — and that you don't leave any bits out.
 
By using a vector drawing program, smooth, flowing, constant-width lines are easy to achieve.

 

[hi-fiber]

is there some way to eliminate the power-down/off thump? I think its hurting my headphones... 

 

[tangent]

It's probably harmless, but since it bothers you, you can move the power supply caps ahead of the power switch, like I did for PIMETA v2.