Lum

I need to build or obtain a small amplifier, most of the in-car ones sold are too big and too powerful.

Is is for in-car use and needs to have similar output power to a typical head unit, however the input will be standard line-level as you would get from a PC or a piece of indoor hi-fi equipment.

There's lots of ICs out there that will do this really easilly, but most of them want a -12V rail which is not available in a car. I can provide the normal car battery feed, or a regulated 12V feed or anything available on an ATX PSU (though I beleive this would sound nasty)

Anyone got any idea how to do this, bearing in mind that the size needs to be kept to a minimum too, assume it's going into a single DIN head unit and there needs to be room for other gubbins too.

Anyone want to build it for me in exchange for cash?

dba

ask here

http://www.talkaudio.co.uk/vbb/index.php?

Graz

Believe it or not I'm an electronics engineer however I don't do much by way of analogue design, mostly software these days.

What I will say however is that the voltage feed to you amplifier is somewhat irrevelent. A clean and stable power supply is essential to good audio design. The 12V feed from the car needs well regulated and filtered otherwise you'll pick up loads of interference from the ignition system, alternator, etc. When designing the power supply you can decide what voltages you need and specify accordingly. However what you should realise is that -12v is only +12v with the connections reversed!

Have a look on Amazon as there will be plenty of books on Hi-Fi amplifier and power supply design.

I would try and find a commercial product to do what you want though. Hi-Fi design isn't that simple, it's not that difficult to build an amplifier but making it sound good is another matter entirely.

rgv_stu

i made one years ago, dug it out the loft while tidying up the other day.
was about 20w rms output per channel. it was a chip commonly found in car radios in the early 90's. think it was a tda2005 ?? i can look later when im at home , i probably still have the circuit diagrams too somewhere.

AndyC_772

iTrader: (2)

A tad misleading, perhaps - swap the connections and you'll soon learn the difference as soon as you plug into anything else, like the signal source for example!

If your amplifier needs -12 as well as +12 then you need either an isolating 12V-12V DC/DC converter or a voltage inverter. You also need all manner of filtering and protection components for the reasons stated above.

Unfortunately, electronics isn't simply about joining building blocks together. There's a lot more to it than that, which is why I get paid to do it!

Without wishing to be blunt, nobody's going to be able to talk you through building one in a single post - you'd be better off getting a good book on the subject and starting from there. If you just want one small amp, your best bet is probably to spend a while looking through things like the Maplin catalogue for a kit with instructions, or a complete ready made unit that fits your needs.

JackClark

Am I missing something? There are tons of small form amplifiers here one for about £12 that's smaller than a dollar bill. http://www.autotoys.com/x/catalog/SU...ER_p_4593.html

This one's even smaller with less power. http://www.autotoys.com/x/catalog/HE...ER_p_4051.html

Lum

I've not yet found anything small enough for what I am trying to acheive. I need something not much bigger that what would be found inside a head unit, and preferably just a board rather than a complete unit, I also need 4 channels, so that one there suddenly becomes huge!
There seem to be chips on the market that do the job even if fed off an unregulated car supply, but I'd still rather just pay someone who knows what they're doing to actually build this

ALi-B

iTrader: (1)

If you build your own, then probably easiest to base it on a pair of high power op-amps such as a LM380 (2.5watts - too small?) That's a pretty poor quality amp, so it depends what you need it for, but it will run off a single rail power supply. Most bigger and bettter quality stuff requires a split rail supply - and that's when things get complex (as mentioned above).

Alternative...Go down your scrappers, Find a ford XR4, Granada V6 Ghia, MK5 1992 onwards XR3, or Orion 1.8 Ghia LX.....they all used seperate power amps to the head unit. 4 channel approx 25-30watts. They don't use RCA scokets though...the latter ford used telephone type connectors (which you'll need to get too), which can easily be apdated and fit RCA connectors on the end


Also look at RadioMobile, Altai, JVC and Goodmans they do make quite small car power amps around the 2x25 watts RMS (well they used to at least)

john_s

iTrader: (1)

Have you looked at the project modules Maplin do? There may be something in there that will do what you want.

Failing that, they may have a power amp IC that may only need a few components to get an amp up and running. I'm pretty sure they used to have some, but I've not looked through a Maplin catalogue for a couple of years.

John.

Lum

I can tell

Maplin don't do anything like that any more, neon overcocking accessories and disco lights and radio controlled car turned out to be far more profitable.

The closest I saw to an electronics project was "solder the LEDs on the christmas tree shaped PCB" woo.

With Tandy gone as well, the only place to get bits from is RS and they don't do fun hobbyist kits.

Henrik

iTrader: (5)

Farnell (i.e CPC) at www.cpc.co.uk do some hobby kits, I believe. Don't know if they do amps though


This might not be what you want, but it's a car amp: http://cpc.farnell.com/jsp/endecaSea...TDA1519A&N=401