Car stereo question

[Caladh]

Next year I will take back to the boat an Ipod with all my CD's ripped to it and connect it either wirelessly or wired to a new cheapy car stereo/radio to play through. I wonder if any one can give me an idea of likely amps useage by just using the amplifier of the car stereo as opposed to listening to CD's which I seemed to remember from earlier this season was IRO about 2 amps.

 

[Ex-SolentBoy]

I am a numpty on stereos, but surely this depends on the power of your speakers and how high you turn up the volume. That in turn will depend on how loud you want to listen to the music and also the level that you recorded at in ITunes?

 

[nigelmercier]

I am a numpty on stereos...

It seems not, as you are quite correct. Watts in equals watts out (give or take a bit).

 

[duncan99210]

So the watts out of the stero system, plus a bit for the internal workings , will give you the power consumption of the kit. If you use the radio route to link to the iPod, then you'll need to add a little bit more to cover that. The instruction leaflet with the stero should give you power consumption figures as well......

 

[noelex]

Car CD players usually use about an 1A with 2 speakers and the internal amplifier.
Playing an MP3 instead of a CD, particularly from a USB stick will reduce this by about 30%.
These are typical figures, but they do vary a bit.

Dim the lighting and measure power consumption of the memory function (most are very low, but on some units its significant and worth discconecting if you do not need it)

 

[noelex]

It seems not, as you are quite correct. Watts in equals watts out (give or take a bit).

The average output of car sterio will only be a bit over 1 watt, but there is a lot of power consumed in display lighting and the motors driving the mechanism as well as losses in the amplifing section. So most units will consume about 10X more watts than they actually put out in music .

 

[Gordonmc]

Another approach would be to use a small motorbike style 12v amplifier instead of a car stereo.
MP3 in, 12v in, 100w per channel stereo out.
All you are powering is the amp at about 90% efficiency.
A tenner on ebay - just search for "12v amplifier".
I am going this route as I have a DAB receiver for radio but want something for recorded music.

 

[Conachair]

Next year I will take back to the boat an Ipod with all my CD's ripped to it and connect it either wirelessly or wired to a new cheapy car stereo/radio to play through. I wonder if any one can give me an idea of likely amps useage by just using the amplifier of the car stereo as opposed to listening to CD's which I seemed to remember from earlier this season was IRO about 2 amps.

My JVC draws 0.7a when listening to the radio or ipod via 3.5mm jack, goes up to 1.2a when the ipod is connected via usb, charges the ipod then as well, this might go down when the ipod is fully charged. I'll have a look later.


If your boat sends a list to santa then one of these should be on it

http://www.tecpel.net/DCM-033.html

 

[concentrik]

.

Because car stereo manufacturers (and domestic too, for that matter) consider high output levels as a positive selling point they are prone to exaggerate them.

To this end they have devised methods of measuring output power which flatter their equipment, one such in common use is Peak Music Power Output often referred to without explanation as PMPO. This is the very highest instantaneous output power the equipment can deliver, often at hideous distortion levels.

The point is, you can't look at the rated output power as an indication of the average continuous current consumption. Unless you are very hard of hearing you are unlikely to demand more than a few watts average output. The source material will have an effect; if you like Radio 1 it will cost you. Their programme output is very compressed with little dynamic range to take account of the specialised auditory requirements of their target audience. Classical piano works are less demanding.

In any case I'd suggest it's less of a problem than you thought. The 'overhead' consumption isn't that significant either especially if you aren't using the CD section (no motors).

 

[Ruffles]

My JVC draws 0.7a when listening to the radio or ipod via 3.5mm jack, goes up to 1.2a when the ipod is connected via usb, charges the ipod then as well, this might go down when the ipod is fully charged. I'll have a look later.

My Aldi unit used 1.2 amps when playing a CD and half that on radio/USB.

Maximum power output is irrelevant. Speaker efficiency could be important if you like your music loud!

 

[robp]

Next year I will take back to the boat an Ipod with all my CD's ripped to it and connect it either wirelessly or wired to a new cheapy car stereo/radio to play through. I wonder if any one can give me an idea of likely amps useage by just using the amplifier of the car stereo as opposed to listening to CD's which I seemed to remember from earlier this season was IRO about 2 amps.

Hi Simon

As others have said, an Amp or so is what you'll use. But if consumption is really critical connect it wired. An FM Wireless transmitter will use some power but could also charge the ipod. Probably though it's not worth worrying about and a neat solution is to mount a cigar lighter socket in the woodwork at a convenient place and use a car Ipod/Iphone cradle with FM Transmitter on a gooseneck with 12V cigar plug on it.

 

[Caladh]

To all who have contributed on this thread, thanks very much. All good info to think about.

 

[mucklestone]

Another approach would be to use a small motorbike style 12v amplifier instead of a car stereo.
MP3 in, 12v in, 100w per channel stereo out.
All you are powering is the amp at about 90% efficiency.
A tenner on ebay - just search for "12v amplifier".
I am going this route as I have a DAB receiver for radio but want something for recorded music.

I would love to see a 90% efficient amp. I have built many and a typical design is nearer 50% efficient if you are lucky and even that is typically often more efficient than one you will buy.... In design you normal aim for and work to 50% efficiency.

With regard to the usage, it totally depends on the unit. Some are ok some are not, they vary so much you need to measure them really. Generally just think how long could you sit in your car before you flatted the battery listening to the radio/cd player? A long time probably. I think ford allow an hour on their stereos as a safe amount of time???

 

[st599]

I would love to see a 90% efficient amp. I have built many and a typical design is nearer 50% efficient if you are lucky and even that is typically often more efficient than one you will buy.... In design you normal aim for and work to 50% efficiency.

With regard to the usage, it totally depends on the unit. Some are ok some are not, they vary so much you need to measure them really. Generally just think how long could you sit in your car before you flatted the battery listening to the radio/cd player? A long time probably. I think ford allow an hour on their stereos as a safe amount of time???

It'll probably be class D. So it's an A to D converter, a Pulse Width Modulator a low pass filter and a fixed gain FET. Very efficient.

 

[mucklestone]

It'll probably be class D. So it's an A to D converter, a Pulse Width Modulator a low pass filter and a fixed gain FET. Very efficient.

Yes car amps are very efficient, (or they can be) but still not much more than what I said. By the time you take into account the processor to drive an iPod interface, a big bright screen i bet you would be lucky to get the efficiency I quoted. The efficiency of the unit as a whole is awful.

Obviously you know your stuff, but unless it was a class A amp (and I have never heard of one in a car) on a 4x50w amp you will probably only be using about 5-10w total output during normal quiet listening yet a unit will still often draw 2-3amps? That is not very efficient. Looking at total output etc I think you are right, but for normal listening there are so many other factors you have to consider.