I didn't understand what is your problem. Usually audio gear for car needs 12 VDC. and not 12 VAC. Are you sure you need 12VAC? Would you tell us the brand/model of your crossover, if it is a commercial one?
OK, I think it's clear now. Your crossover is a home type and needs 120VAC to work. You want to use it in your car.
I know two ways to solve this problem, but I think some of them would be a little complex if you don't have some experience in electronic design and mounting.
You can put an inverter (12VDC to 120VAC) to feed your crossover, but, as far as I know, most of the commercial types produce output waveforms that are not very good for audio applications. Maybe some fellows here at the Forum know some commercial types designed for audio.
You can modify the power supply of the Xover and adapt there a simple switched mode power supply, working with 12VDC at the input.
Another possibility is on building your own crossover. There is another thread here with indications about "ESP audio projects", when you you find information about how to build a simple car crossover and preamp.
no it doesnt run on 120VAC, It runs on 12VAC, i did have it running from mains power (240VAC here in OZ) into a transformer stepping it down to the 12VAC. Sorry if i wasnt clear enough in my description of it . My question was simply if i could turn 12VDC into 12VAC. The way i thought i could was maybe to use a diode (one that converts AC to DC) and to reverse the polarity. This probably wont work its just a thought. Unfortunately power supplies are not my forte.
thanks for your help By the way it is based on the 3 way active linkwitz (I think thats how its spelled) design.
It will not work as you think with the diode and it seems your Xover has just the transformer placed out of the box to avoid hum or to allow little box mounting.
There are many possibilities here too. I'm assuming two wires from the transformer to the Xover:
- full wave rectification and unregulated power supply inside the xover: you don't need nothing more than connect the battery to the 12VAC input of the xover with no worries about polarities. Usually works fine since you take care of ground loops;
- full wave rectification and regulated power supply inside the xover: You might might have problems if the regulated output is over 9 or 10V, but it can work too at the same way of the first possibility;
- half wave rectification in both cases above: take care about the polarity of the ground of the Xover, it must be the of the rest of the components of your system (usually negative battery tap) and must be considered when connecting the battery to the 12VAC connector of the Xover;
- any kind of voltage doubler or switched mode circuits inside the Xover: considering you don't want to change nothing inside the xover, you will need an circuit called inverter or an sinusoidal generator with enough power and output amplitude to support the Xover, working in 60Hz or more. I think there are projects about it in the Internet.
I think the first think to do is discover how this xover is powered and analyse the possibilities above. I think the first or the second are the bigger probabilities of working.
Thanks for your replies
After more inspection of the schematics it in fact runs off +/-16VDC. I should have looked at it before i posted Just so you know im not that familiar with electronics but very interested as im in my first year of an Electronics degree Is there an easy way to supply a negative and positive rails off of the 12VDC source. If you need the schematics i can email to you. Again thanks for all your help
I may have read it wrong but wasnt the article about how to make the +/- supply rails plus the ground, but does not talk about stepping up the voltage. Thanks for the link as it has solved half of my problem
So, your xover works with +/- 16V. I think you have a couple of possibilities here too:
- the virtual earth proposed in ESP demmands modifications in your xover and has little output current capacity. I think it would be a little hard to implement in your case, but, if you decide to go on this way, I can say usually +/- 16V circuits will work fine with +/- 12V;
- I´ve built, many times, a simple self oscillanting circuit to feed this kind of gear. It works on 30 or 40 KHz and you can use 3 terminal regulators at the output to regulate it. It´s easy to mount and you can find the components in any surplus store. If you were interested, let me know and tell me an e-mail address when I can put the schematics and other instructions. Of course, it demmands some electronic skills, but you can mount it without mess your xover and learn enough until felling yourself confident to connect it to the xover.