Notices

I was bored and i have my health issues causing me to remain stationary, so i decided to use my time to complete a project i have been planning for some time, an ADD ON amp (can be made to fit inside mugen cover), this amp is a 2x3W class D i bought from DX for 5-6$!!!

The Setup:
The WMA2012 amp is soldered directly to the jack plug so it is very stationary, and as you can see the power is drawn directly from my charge plug (Goto Battery Thread Post #2 for more info), the charge plug is always connected to the Dual Scud so this serves as a power source for many things if needed (Amp, HIGH Power flash-light etc.).


WMA2012 Info:
This amp is simply awesome and take it from someone how has been building HIFI for 10+years (AMPS, Speakers, Filters A & D and even speaker units), this amp delivers very good power and it does it from 2.5V-5.5V making it ideal for single cell lithium operation or USB powered.
Can be bought from DX (LINK) for only 5.30$ shipped



Power Usage:
Well not much, there is no heat loss because the amp is VERY efficient and even on full this ADD ON will rock the party long time


And since were on the subject can't resist to throw my home amp in here as well


HOME AMP: 2x 250W+ (4 Ohm), lets just say when connected to previous speakers handling 500W (2 Ohm) with no distortion at all.
The amp is build up in 2 stages, A TDA7294 and A HIGH Power transistor stage helping the power along, the transistors + TDA7294 can handle 600W+ (MAX Power) together, besides that if 4 or 8 Ohm is needed it can be bridged to 1x 1000W (4 Ohm)
But with the current transformer it is limited by input power to something like 2x 300W+ Max Power

Here are the schematics and more pictures of my home amp.
TDA7294 NPN_PNP.zip
NOTE: The pictures are from the old version (same as the current one in use, just that the current is 2x on one cooling plate (Pentium 4 Cooler )

Haha, home amp use ATX power supply cover, doesn't it? Or in fact it uses that as own power supply and just share same box?

Fine thing with portable amp, but are You sure it'll fit into mugen cover inside with dualSCUD mounted at the same time? It seems for me that there is not much space left...

Anyway, it's always possible to carry it with You on pocket - it's really small. Incorporating also jack port on the other side make it compatible with big jack/jack speakers as well

On the other hand, they're are many real life situations for using this? Most things that You connect N900 to through 3.5 jack got own amplifiers inside... Still, nice mod

Long time ago i worked on pocket amplifier (old days when pocket mp3 players weren't obsolete), people we're designing really nice small amplifiers. Although i remember, that most of the time they recommended to use standard batteries instead of rechargeable - due to some kind of voltage stability and different audio sound on different SoC of accu (some kind of distortions, but harder to catch due to being stable at given SoC). How well your amplifier handle this? It's really cheap, and if it would be immune to voltage changes (our Li-Po provide very different voltage during discharging) it would be indeed great. I know it operates at vide variety of voltages, but doesn't it "calibrate" itself on start to given voltage, and voltage change during long playback will distort sound?

Yes the home amp is in a ATX case, was big enough so why not
The power comes from a 150W Ring Transformer that inside there also, the hole amp assembly is very "small"


With some creative placement the amp can just fit in the cover....
But having it inside still create other problems, like having the audio connection go out and in etc....

But this amp is just awesome and just wanted to share it, and also throw my home amp in, been using the home amp for over 2 years now... it's really good.

Well no matter what you connect to this chip it just delivers and all battery's i have can easily deliver the MAX 5W it takes.

And the Audio Quality is just awesome, really no change from this and my home amp, no matter if it is small speakers or 12"+ you connect or if it is 4 or 8 Ohm it just plays and remember if you have VERY good speakers (High Sensitivity) 1W is more then enough to play really LOUD

Tomorrow i will attach it to my main speakers (3 Ohm) and let it rip, but not now, the wife and son are asleep and it is almost 2 at night.

And on the power note, have been playing for 1 hour+ at very low volume, someplayer and screen off and i cannot see any drop in batt %

some really great modding there, nicely done.
id love to see how it looks with in the mugen cover.

makes me want to finish some old projects i have lying around

About placing it inside mugen cover and audio cables going in and out - solution may be to solder it into N900 mainboard and use dead-flashing pins slot (under battery) to put cables inside mugen cover without outside route. If cable is flat enough - and audio cables may be very flat without sound problems - it will not stop battery from fitting in socket. Ho ever, this would need N900 disassembly (no problem at all cause it's easy), and i don't remember how shield was placed around audio jack on N900 = how hard it would be to solder it. Jack plug is quite big as for today's standards, so it shouldn't be too hard, if shielding doesn't permit approach.

If also jack port could be incorporated into mugen cover - just like Your charging plug - then You would have another jack port in N900 cover. Stock jack would be to use without AMP, and the second to use with.

Using an electronic part that i can't recall name for now, You can even make it that, only when something is plugged into amp-jack, they power to amp is activated. You know, switch that activates itself on closing other connection - it will work the same way as headphones detection on N900 (side note - headphones detection can be also relayed to that second jack port).

That would be ultimate maintenance free solution. You just plug something into amp port located on Your cover, and AMP automatically get powered up and start working. You plug into normal N900 audio port, and everything is "regular" way.

Yes but still i will be a pain to operate if it is inside the cover....
Of course further modding and wiring can exclude the jack plug by connecting the input directly where the Mainboard is connected to the 3.5 output. and i do have enough VERY small switches laying around, just need to connect a DUMB jack in so the N900 turns off internal speakers.

Then one could put a 3.5 stereo jack in the cover, this will then be speakers out (AMP), then just make a jack to the clamps i use or to banana plugs etc...

Hahaha, we bought have written about similar things, except that i don't really like idea of disabling internal speakers once for all. Check my last post (you were faster) maybe You will like some of my ideas or even make them better.

No not once and for all, just when needed, put in DUMB jack and this turns off speakers because it thinks headset has been connected.

Yea, but check for inserted jack port can be relayed to second jack port also - then no need to using dumb. If, at the same time, we incorporate another check only on second jack port (for example, "probing" other portion of jack plug) and use it to disable/enable amplifier, we got 0 additional effort solution. That electronic parts i still can't remember name for are very small, if used for such a low voltage like <5v.

I really, really can't remember it's name... Is the same thing that start water cooling pumps connected to 230V when computer starts, in desktops sets. Of course ones for 230V are MUCH bigger, but as i said max 5v oneis so small that can be put inside cover with ease.

Of course doing everything like this is little hassle, but after that You don't even need manual switch to turn amplifier on/off. Less cutting on Your cover, less elements that can possibly break due to mechanical moving parts