Line driver?

[audiobahnkid592]

Is there anyway to build just a RCA line driver to take one input signal and have it put out 4 or 5V output on 3 outputs? Has to operate off of car voltage.

[theAnonymous1]

Forget the "line driver" car audio mumbo jumbo. What you want is called a preamp.

Here is a circuit designed specifically for use in a car....

http://sound.westhost.com/project32.htm

If you don't like that circuit you can build nearly any preamp and use it. There are plenty of them around if you do a search.

The power supply for a preamp in a car is probably more complicated then the preamp itself. If your up to building your own you can try this one.....

http://sound.westhost.com/project95.htm

I've taken the easy way out for some Linkwitz Transform circuits I'm building. I went ahead and bought some DC-DC converters.

If you find a project that you feel confident building and need a supply, I can sell you one of mine (I have extras).

These sell for $70 new, but I can sell you one for $10.....

DATEL BWR-15/330-D12

http://www.newark.com/jsp/Power+Prod...sp?sku=18C3387

http://www.datel.com/data/power/bwr7-10wa-series.pdf

OR, you can just BUY a "line driver".

http://cgi.ebay.com/Pac-Turbo-1-Turb...QQcmdZViewItem

[cl_chemie]

Do you still have any of the Datel DC-DC converters? I would -love- to get my hands on one for an equalizer project I've been working on. I prototyped the equalizer and was almost ready to solder everything together when I realized that supplying power wouldn't be straightforward in a car. I found the Datel units after a lot of research but was turned off by the $70! $10 is a lot more in the range of what I was thinking

As an alternative, would it be possible to use a PWM to regulate the battery voltage down to 5V and then upconvert again using the following from TI:

http://focus.ti.com/docs/prod/folder...ch010512d.html
http://focus.ti.com/lit/ds/symlink/dch010512d.pdf

or:

http://focus.ti.com/docs/prod/folder...cp021212d.html
http://focus.ti.com/lit/ds/symlink/dcp021212d.pdf

I was hoping that the output from such a pairing would give me a steady power supply since the fluctuating battery V is regulated upfront.

I'm really interested in the Datel units regardless, but also curious if the strategy I have proposed would work for low-power devices. Thanks for any insight!

[theAnonymous1]

I've already let a few go and would like to keep most of whats left, but I can spare another I guess.

[dangus]

There's little DC-DC converters at Mouser and Digikey... they start at around $15 and up. I'd suggest getting one that does +/-15V and regulating down to 12V with 3-terminal regulators if you're fussy.

[Perry Babin]

cl_chemie:

If you don't find anything else, you can have this one for the price of shipping (~$7).

http://www.bmpt1.com/temp/psboard01.jpg

[cl_chemie]

Anonymous1: A few other alternatives seem to have opened up so let me explore those before I request one of your Datel units. Thanks very much for the offer though!

Dangus: If I'm thinking of the same units that you are referring to, I had one major concern that held me back from using those. Namely, the given input range is either 12V or 15V +/- 10%. This gives me a range of 10.8-13.2V or 13.5-16.5V. I'm expecting the car battery to fluctuate between 12-14V conservatively (although I thought it would be better to account for at least 10-14V). Thus, a 12V version will be overloaded when the car is on (14V) and a 15V version will be under-volted when the car is off.

I'm guessing that the 12V version uses components that cannot tolerate >10% input. However, from what I understand, an underpowered component can still be functional but will not always give predictable results. If this is true, I can use a 15V version and then regulate down to 12V as you suggest in order to smooth out irregularities brought on by voltage drops . Am I on the right track here?

This was also the thinking behind the solution I posted above, except that I figured a PWM could regulate a very wide range of V very efficiently. If anyone has comments on that setup vs. the above they would be appreciated!


Perry: That's a very kind offer and I am definitely interested depending on the validity of my statements above. The only thing that I'm a bit worried about is that your solution is a full-strength PS for higher-wattage projects and I'm afraid it would be wasted on my little equalizer. Also, should I decide to produce a couple more of these equalizers it would be nice to have something that is readily available vs. a custom one-off solution. I will definitely get back to you though regarding your board. Thanks!

[jackinnj]

Originally posted by audiobahnkid592
Is there anyway to build just a RCA line driver to take one input signal and have it put out 4 or 5V output on 3 outputs? Has to operate off of car voltage.

In an automotive environment you have to contend with noise and (potentially) long cable lengths. The line driver chip takes a single-ended output, converts it to a balanced output -- then the line receiver does the opposite -- in this way you avoid noise pickup over the cable.

You don'thave to use the specialist chips like the Analog Devices SSM2141 and 2142 shown in the attachment -- the same thing can be cobbled together with discrete opamps and some resistors -- and ADI shows how on their website.

With respect to bipolar power for the line driver -- the transistors in inexpensive PWM chips like the SG3524 and SG3525 are sufficient to drive a push-pull DC-DC converter -- you can get the transformer core you need from a busted PC power supply.

Take a look at the SSM2142 data sheet on Analog Devices website.