Notices

The crackle ended up being a faulty TRS cable, between the BT unit and the car head unit. How embarrassing!

I had no luck getting the VMA2016 to actually work. There conflicting wiring diagrams going around on the internet; some showing earth in different spots, and unclear information on the use of the EN (enable) pin. So it's in the parts bin for the moment. Might get a preassembled VMA2016 board to see if that will help (original issue was low sound volume).

Anyway, I rebuilt the whole unit to neaten it up, and put the power on a seperate circuit. The LM317T was getting hot (burnt me), so I fitted a makeshift heatsink, which brought it down to 69.5C maximum with the box open (measured on the body of the LM317T). Also drilled some vents into the top of the box to aid with cooling. If it becomes an issue, I might look into mounting a small fan in the side of the box.

Pictured attached for dr_frost_dk!

Updated POST #1 with schematics and more pictures on my home amp on request

Awesomeness, dr_frost! Since I bought a second N900 as my spare unit, a couple of weeks ago, and that means I'll be using my two N900's for quite a bit longer, I am considering taking your advice and building myself an amp like this.

Thanks for sharing!

Your welcome

and 5spdvl how is the BT coming along?

It's alright. The VMA2016 I bought was a dud. Well, I couldn't get it to work. It only produced static, and got very hot. Seemed to be some discrepancies in the wiring diagrams I found. I'll buy another, but mounted to a board instead.

But lately I've noticed that if I don't drive my car for a few days, the battery struggles a little.Need to put a relay between the battery and BT unit, so the ignition turns it on. And the sound continually drops the left channel only - this is because the TRS socket it loose. Planning on fixing that soon.....been too busy enjoying holidays and fixing mate's cars!

Just made a little "happy" speaker with the VMA2012, KBTEL Battery and 2x 3W speakers from DX

Has a good sound, better then expected from something that ways about 100g.

Application, for "long" journeys on the EV Moped (Limited Speed 30 KM/h by Danish law....), makes the time go by faster :P.

Only thing left to do is put in a charge plug so i don't need to open it up to charge.

The 1220mAh battery should last over 1 hour of play time so that would be plenty for the application

Additional info: Plays >3x as loud as N900, and here we are talking about clear sound, not that the N900 isn't impressive in that area.






EDIT: After using this amp for more then 4 hours and only seeing a battery drop to 80%, i think i can say this will blast on full volume for some hours, this i will confirm when the weather is NORMAL!!!, damm windy and raining right now, not the conditions for this amp sitting exposed on my Electro Ciao.
Right now there's a big storm over DK.....

^ That's really, super cute.

I doubt anyone would take you seriously though after seeing the happy face you drew on it.

I guess your right but i couldn't resist

But i will say that this little box really throws some sound out, if it was tuned to the speakers + bass reflex it would really be impressive sound wise.

Those speakers are pretty good.

Nice, really, very nice! What about higher frequency sound (as opposed to bass) with those speakers? And overall balance between basses and high pitches?

/Estel

I would say so, don't expect 20Khz but all in all they are full tone, as i wrote on DX i would estimate them to 80-14000Hz, i don't have the time to measure them yet, but im use to making audio and i would call them at that freq.

Also VS. my asus laptop the audio is many many times better.

UPDATE: have been using it at home with N900 and laptop and have played for 1 hour+ but at low (normal levels) volume and so far it has only used 10% of the 1220mAh battery.
Have to make a new measurement on usage at full power (as much as the small speakers can take).