Car Radio in Van

G'day Allan B

If the RCA's are line out and constant volume, how does and amp hooked up to them as the sound driver source vary the volume of the amp?


Cheers
Ross M

Thank you for your reply.
I have been reading about your comments. Am I correct in understanding that the mismatch between the impedance of the line out and a connected speaker or headphone (100 - 600 ohms vs 8 - 30 ohms) is too large for a workable connection? On the other hand, a connection between the speaker and headphones would be workable since their impedance values are closer together?
I am wanting to set up the option where the radio can be listened to through the speakers or through headphones. I have only the front speakers connected to the radio, so, if I were to set up a switch to disconnect these speakers from the radio, could a direct connection from the poles of one of the unused rear speaker to headphones be a possible solution?

You could wire a 3.5mm std stereo socket to the rears and just alter the fore aft Fade setting when Headphones are used.
Best to check if the commons ie negative speaker wire is common to all channels or each negative is separate.

They can be one or the other.

For example, if you connected the two channels negs/earths together for the socket it may begin to overheat the output drivers of the radios amp section and may also sound a bit fuzzy.

If they are all common negs/earths then no problem.

Ross M

Thanks, Ross.
How does one check whether if negatives are common or separate?

JohnKT
I only discovered it when finding why a friends radio got hot and mine didn't.
A knowledgeable person at a car radio installer might know which do and don't.
My experience with that was fitting a Fujitsu Ten unit, in a Toyota Lcruiser, it has two wires and the negs weren't common in the plug to the unit.

Some Mitsubisji units used common and therefore three wires, one common fed the front speakers and same for rears.

As far as I can tell it doesn't damage the unit, well not straight away, but it uses more power/amps to run the unit when it is happening.

If you have a multi meter and read the resistance between the earth/neg wires concerned it would show VERY LOW resistance f they are common whereas the separate negs may show a higher reading of ohms.

If required I can go and check that as I have Fujitsu Ten in the shed and it has the separate system. Also may have other radios which may be different so I would have to investigate, hoping to have confirmation one way or the other.

Some one else may know immediately though and be able to say if you tell us the name and product ID of the radio unit.

Cheers
Ross M

Ross M

I don't know about your amplifier but mine has a volume control on it that works separately to the actual audio source. Maybe you got yours from Aldi. Sorry mate but that is such a simple question to answer. Stop stirring him.

Phil

From the discussion I had not expected the following to work but it does. Am I missing something? Any comment to put my mind at rest?
I bought a small earphone amplifier powered by a AAA battery which I connected to the rear line out RCA plugs from the radio via a RCA to 3.5mm headphone jack adapter (the input on the amp is a 3.5mm jack). The headphones were the connected to the 3.5mm jack output on the amplifier. The sound can be switched between the attached front radio speakers (I don't have rear speakers connected) and the rear out line using the fade control on the radio. The volume to the headphones is then adjustable by the volume control on the radio.
Thanks, John.