Starting a project - Transistor problems

Hello all. I've just started my first real electronic project, and therefore I've come to this forum

I'm trying to achieve volume controlling from an Arduino for an external sound device, and I've been searching like a mad man.

What I guessed would be the easiest way to do this was to use a transistor and wire my sound source, sound destination and a analog output from the Arduino.

This does not work as it is supposed to. When I send analog signal 255 (max of 5v Arduino) the sound start flowing, but when decreasing it to 180 I'm not able to hear any lower in the sound. I guess I'd just turrn it more down, but anything under 150 simply means no sound at all.

What could I be doing wrong, and is it at all the right way to go trying to manage volume from a second signal?

Thanks,
Excizted

Post a schematic of what you have now.

It's necessary to have a schematic to provide a starting place; and then make a plan for how to get from where you are, to where you want to be.

A schematic to consist of what? ;/

A schematic of the circuit that you connected to the Arduino, of course.

The transistor I am using:
http://www.sparkfun.com/datasheets/Components/BC546.pdf

I've got:
Sound Out + and -.
Sound Speakers + and -.
Arduino Analog Out +, no minus/gnd since the sound and arduino shares ground.

To the Collecter I wired up my Sound Out +.
To the Emitter I wired up my Sound Speaker +.
To the Base I wire the Arduino Analog Out.

The Sound Out minus and Sound Speaker minus are connected directly to each other.

If this (attached) is what you mean, I'm gonna go ahead and say it's probably not gonna work very well. A voltage-controlled amplifier is a pretty complex circuit, as you'll see from some of the links. You can get a monolithic IC to do it, but many of them are expensive, and you may need special power supplies (positive & negative, at least) and/or special interface circuitry.

You are trying to use a low power DC transistor as a high power AC variable resistor.
They are completely different.

If your Sound Speaker has an amplifier inside then you can use a Jfet and a few resistors and capacitors to control its volume.

A TDA7052A little power amplifier IC (0.88W at clipping into an 8 ohm speaker with a 6V supply) has a DC volume control built-in.

Ok then. I thought a transistor would do, since thats what a friend told me.

What would be the best components to control volume of several speakers with an Arduino then?