I am looking for something as cheap as possible, but still actually work.

Found this on ebay, will it work?
http://cgi.ebay.com/ws/eBay...em&item=190671141253

Looks like a laptop or Playstation power supply. 4 amp output..would probably work if you didn't blast the thing out at 100 watts per channel

http://www.ebay.com/sch/i.h...=20+amp+power+supply

happy shopping.

if you want it to "save" your radio settings after you cut it off, look into getting a small 12v battery (like from a UPS you would use on your computer), plug the power supply into the UPS so it only takes 1 plug from the wall, wire in a line from the batterys inside the ups to the 12v always hot into the radio, wire in the power on and the "head light" power to the power supply, along with all the grounds to the power supply, and attach a ground from the UPS battery to the power supply battery... USE DIODES FOR SAFEY!

quote Originally posted by dratts: Right! Ac in, ac out. You can't run a 12v dc radio on a transformer.

??????????? all right you confused me there. All of my 12 volt dc electronics for cars work on transformers. They say transformers right on the cases. I have 12v dc tvs and radios all over the house and garage running on 12v dc transformers and have been for years. So your saying im doing the impossible ? If im not mistaken even your home furnace blower motor is 12 volt and running off a 120 v ac to 12 v dc transformer. They run for 20 years. In a power outage, you can run your furnace off a car battery.

quote Originally posted by rogergarrison: ??????????? all right you confused me there. All of my 12 volt dc electronics for cars work on transformers. They say transformers right on the cases. I have 12v dc tvs and radios all over the house and garage running on 12v dc transformers and have been for years. So your saying im doing the impossible ? If im not mistaken even your home furnace blower motor is 12 volt and running off a 120 v ac to 12 v dc transformer. They run for 20 years. In a power outage, you can run your furnace off a car battery.

There is no such thing as a dc transformer. A transformer requires ac voltage. If you add a rectifier it can turn the output ac to dc. At that point it is more than a transformer. It is a dc power supply at that point. I don't know why so many smart people are arguing this point. It's basic electronics.

quote Originally posted by dratts: There is no such thing as a dc transformer. A transformer requires ac voltage. If you add a rectifier it can turn the output ac to dc. At that point it is more than a transformer. It is a dc power supply at that point. I don't know why so many smart people are arguing this point. It's basic electronics.

100% correct. This is indeed very basic electrical theory and (for those who don't like theory) practice. A transformer is just a device with two or more inductively-coupled windings ... or even a single tapped winding ... usually coupled by a core of magnetic material. They are, by definition, AC in / AC out devices. The current through the primary (input) winding must be AC for the transformer to induce any voltage or current in the secondary (output) winding. If a device has DC in or DC out, it's more than just a transformer.

[This message has been edited by Marvin McInnis (edited 08-20-2012).]

Just to stir the pot, technically a transformer can be DC as well.

Example you say - look at the ignition coil on your car.

HOWEVER were are talking about a pulsed DC signal - a transformer can only work when there is a change in voltage level on the input, the expanding/collasping magnetic field that is produced by the input is what generates the current flow in the output winding of a transformer.

But, YES, it is impossible to have a pure DC output from a transformer without any rectification - the only function of a transformer is to step up or step down an inputted voltage (AC or pulsed DC).

[This message has been edited by Mickey_Moose (edited 08-20-2012).]

Sorry to hijack...

So if I want to hook up my entire stereo system:

Kenwood KAC-9103D--Mono Class D Amplifier for my two subwoofers
2 MTX T4500 subwoofers... cheap things I wouldn't put back in a car, which is why I want a setup in my garage for parties
Alpine CDA-9856 head unit. Currently in my sister's car because I didn't know if I still needed it or not
Alpine MRP-F450 4 channel amp for speakers that I don't currently have... but I could get some on the cheap.

All I need is a battery and a conversion from AC to DC? Sounds wayyy too easy...

And could I do it with an old stock head unit from a 90's car or do I need to get my head unit back from my sister?

Ok, so if I understand what your saying, all these 'boxes' that say transformer on them are incorrect ? Theyre not transformers at all. How come my voltmeter shows them as 12-13.5 volts DC. If I set my meter to read AC volts and connect the probes, it reads zero. So according to the meter, it is putting out DC (12+) voltage and no (zero) AC voltage. Just asking, not arguing.

quote Originally posted by rogergarrison: Ok, so if I understand what your saying, all these 'boxes' that say transformer on them are incorrect ? Theyre not transformers at all. How come my voltmeter shows them as 12-13.5 volts DC. If I set my meter to read AC volts and connect the probes, it reads zero. So according to the meter, it is putting out DC (12+) voltage and no (zero) AC voltage. Just asking, not arguing.

It does have a transformer in it, but it performs more than just a transformer. It also has circuitry(rectifiers/diodes) to convert the AC output of the transformer into the DC current you're seeing with your meter. The transformer itself only converts the high voltage AC to low voltage AC and the output is converted into DC by way of the additional circuitry. The labeling isn't necessarily wrong, it's just incomplete.

[This message has been edited by Rallaster (edited 08-20-2012).]

quote Originally posted by Rallaster: It does have a transformer in it, but it performs more than just a transformer. It also has circuitry(rectifiers/diodes) to convert the AC output of the transformer into the DC current you're seeing with your meter. The transformer itself only converts the high voltage AC to low voltage AC and the output is converted into DC by way of the additional circuitry. The labeling isn't necessarily wrong, it's just incomplete.

Or vice versa converting the high AC voltage into an even higher AC voltage. For instance a transformer to power neon lights.

A transformer is just seperate sets of windings around a core, that's it nothing more. The number of windings in proportion between the 2 or more sets of coils determines the voltage output based on the input. More windings on the output side results in increased voltage, less windings on the output side results in decreased voltage (if I remember correctly). Also, the thickness of the conductors used will determine how much amperage the transformer can deliver. All a tranformer can do by itself is convert AC to AC, with a bridge rectifier or the use of diodes, the AC output can be converted to DC, but those are seperate components. There will be nominal voltage loss from the bridge rectifier or diode, but probably not enough to measure without a osciliscope. The bridge rectifier or diodes are not transformers, they do not in any real substantial way change the amount of voltage they are given, all they do is convert the AC feed to DC.



If I remember correctly, elctronics courses were several years back, that is the configuration for a bridge rectifier. It's 4 diodes in one casing. Note it is a bridge rectifier, not a transformer, that makes AC voltage into DC. What people are saying, as in the quoted post, is a transformer does nothing but convert AC to AC, it's a bridge rectifier or some diodes that converts the AC to DC.

Also, just a note, if you feed DC into a transformer, you end up with a electro-magnet.

[This message has been edited by Khw (edited 08-20-2012).]

quote Originally posted by rogergarrison: Ok, so if I understand what your saying, all these 'boxes' that say transformer on them are incorrect ? Theyre not transformers at all. How come my voltmeter shows them as 12-13.5 volts DC. If I set my meter to read AC volts and connect the probes, it reads zero. So according to the meter, it is putting out DC (12+) voltage and no (zero) AC voltage. Just asking, not arguing.

What you have is refered to a 'wall transformer' which has inside the 'box': a transformer (step down), bridge rectifier and a regulator. It is essentially an AC to DC converter. It is not strictly a transformer per say - it's just about the terminology and what has become the accepted name to call the device.

If you walk into any electronics store and ask them for a 'transformer' so you can charge your phone that is what they will sell you - it has become the accepted 'description', but if you do a search for 'transformer' on Digikey (or any other electronics parts supplier) you will get listings for only just the transformer ('wall transformers' will also show up, since transformer is part of the name - you have to search for 'wall transformer' to only bring up those boxes you are talking about).

It is like saying electronics above - on one hand it refers to a component like a stereo (or tv) where as on the other it refers to the actual parts inside that makes up the stereo.

quote Originally posted by theBDub: Sorry to hijack... So if I want to hook up my entire stereo system: Kenwood KAC-9103D--Mono Class D Amplifier for my two subwoofers 2 MTX T4500 subwoofers... cheap things I wouldn't put back in a car, which is why I want a setup in my garage for parties Alpine CDA-9856 head unit. Currently in my sister's car because I didn't know if I still needed it or not Alpine MRP-F450 4 channel amp for speakers that I don't currently have... but I could get some on the cheap. All I need is a battery and a conversion from AC to DC? Sounds wayyy too easy... And could I do it with an old stock head unit from a 90's car or do I need to get my head unit back from my sister?

No, all you need is a car battery (with a battery charger of some sort to maintain/charge the battery). There is NO CHEAP way of plugging that type of system into the wall unless you are able to gut some old electronics.

quote Originally posted by theBDub: Sorry to hijack... So if I want to hook up my entire stereo system: Kenwood KAC-9103D--Mono Class D Amplifier for my two subwoofers 2 MTX T4500 subwoofers... cheap things I wouldn't put back in a car, which is why I want a setup in my garage for parties Alpine CDA-9856 head unit. Currently in my sister's car because I didn't know if I still needed it or not Alpine MRP-F450 4 channel amp for speakers that I don't currently have... but I could get some on the cheap. All I need is a battery and a conversion from AC to DC? Sounds wayyy too easy... And could I do it with an old stock head unit from a 90's car or do I need to get my head unit back from my sister?

Brennan. A battery and a battery minder. Make sure you get a power minder with high enough amperage. Most are 2amp trickle or 6amp. I've got a large one I bought for my truck (it is on a dolly). I pad around $100 for it, I think it has a much higher amperage setting. This would be perfect. Personally I put mine in an ice chest and haul it around to parties. Motorboatyourself.com is an awesome information forum if you wanted to go that route.

quote Originally posted by Khw: Or vice versa converting the high AC voltage into an even higher AC voltage. For instance a transformer to power neon lights. A transformer is just seperate sets of windings around a core, that's it nothing more. The number of windings in proportion between the 2 or more sets of coils determines the voltage output based on the input. More windings on the output side results in increased voltage, less windings on the output side results in decreased voltage (if I remember correctly). Also, the thickness of the conductors used will determine how much amperage the transformer can deliver. All a tranformer can do by itself is convert AC to AC, with a bridge rectifier or the use of diodes, the AC output can be converted to DC, but those are seperate components. There will be nominal voltage loss from the bridge rectifier or diode, but probably not enough to measure without a osciliscope. The bridge rectifier or diodes are not transformers, they do not in any real substantial way change the amount of voltage they are given, all they do is convert the AC feed to DC. If I remember correctly, elctronics courses were several years back, that is the configuration for a bridge rectifier. It's 4 diodes in one casing. Note it is a bridge rectifier, not a transformer, that makes AC voltage into DC. What people are saying, as in the quoted post, is a transformer does nothing but convert AC to AC, it's a bridge rectifier or some diodes that converts the AC to DC. Also, just a note, if you feed DC into a transformer, you end up with a electro-magnet.

I was speaking to his specific case, which, if I understand you correctly, my description was correct.

Just for reference, I really only know enough to get myself into trouble. I can identify most of the specific components, but I am largely unable to explain exactly what they do, let alone how they do it.

quote Originally posted by Rallaster: It does have a transformer in it, but it performs more than just a transformer. It also has circuitry(rectifiers/diodes) to convert the AC output of the transformer into the DC current you're seeing with your meter. The transformer itself only converts the high voltage AC to low voltage AC and the output is converted into DC by way of the additional circuitry. The labeling isn't necessarily wrong, it's just incomplete.

Excellent explanation.

quote Originally posted by Khw: A transformer is just seperate sets of windings around a core, that's it nothing more ... All a tranformer can do by itself is convert AC to AC, with a bridge rectifier or the use of diodes, the AC output can be converted to DC, but those are seperate components. There will be nominal voltage loss from the bridge rectifier or diode, but probably not enough to measure without a osciliscope. The bridge rectifier or diodes are not transformers, they do not in any real substantial way change the amount of voltage they are given, all they do is convert the AC feed to DC.

Also a good explanation. One detail correction, though. AC voltages are usually expressed as RMS voltage (average effective "heating" value) rather than peak voltage, but the DC output from the bridge rectifier will be the AC peak voltage (less two rectifier diode voltage drops ... ~1 volt each). For sine wave AC, the peak voltage will be ~1.4 (actually the square root of 2 = 1.414...) times the RMS voltage. Thus the DC output from a "12 volt RMS" transformer plus a bridge rectifier will be about 15 volts. Similarly, if you run standard power line 120 VAC through a bridge rectifier the DC output voltage will be ~168 volts.

quote Originally posted by Mickey_Moose: Just to stir the pot, technically a transformer can be DC as well. Example you say - look at the ignition coil on your car. HOWEVER were are talking about a pulsed DC signal ...

Yes, but the spark coil in a Kettering ignition system doesn't actually function as a transformer. It uses the primary winding to magnetically saturate the iron core, switches off the current in the primary, and then uses the collapsing magnetic field in the core to induce a voltage in the secondary winding. The resulting spark voltage is substantially higher than if the spark coil was being used as an ordinary transformer. FWIW, a capacitive-discharge ignition system does use the spark coil as a pulse transformer, but it also applies substantially more than 12 volts (often >100 volts) to the coil primary winding.

In a more general sense, as long as you don't saturate the core a transformer can't "tell the difference" between an AC square wave and pulsed DC. In fact, if the two windings are electrically isolated from each other the output will be identical in either case.

[This message has been edited by Marvin McInnis (edited 08-21-2012).]

Just to wander around some more. Nobody has mentioned that we're talking "full wave" bridge rectifier here. You can get dc out of a half wave rectifier too. Just not as much.

One caution about using an automotive battery charger or "battery tender" in conjunction with a 12 volt battery to power electronic devices. Many newer electronic "smart" chargers/tenders impose narrow high-voltage spikes on top of the base DC charging voltage. The purpose of these spikes is to more effectively restore (i.e. desulfate) a battery in poor condition, but they can possibly harm some electronic devices that are expecting a relatively smooth and stable 12 to 14 volt supply. This is one case where an old-fashioned, cheap-and-simple "dumb" battery charger may be the best choice.

[This message has been edited by Marvin McInnis (edited 08-21-2012).]

quote Originally posted by Mickey_Moose: No, all you need is a car battery (with a battery charger of some sort to maintain/charge the battery). There is NO CHEAP way of plugging that type of system into the wall unless you are able to gut some old electronics.

Haha! Insane... thanks! I don't care about cheap--I just have wanted to do it for awhile. This is awesome.

quote Originally posted by ls3mach: Brennan. A battery and a battery minder. Make sure you get a power minder with high enough amperage. Most are 2amp trickle or 6amp. I've got a large one I bought for my truck (it is on a dolly). I pad around $100 for it, I think it has a much higher amperage setting. This would be perfect. Personally I put mine in an ice chest and haul it around to parties. Motorboatyourself.com is an awesome information forum if you wanted to go that route.

My buddy here at school did that on his ice chest and we take it to the river. I didn't even think of that until now... So many possibilities... Thanks!

quote Originally posted by theBDub: My buddy here at school did that on his ice chest and we take it to the river. I didn't even think of that until now... So many possibilities... Thanks!

My has a wet/dry box. Holds about 48 beers or 30 pack and plenty of ice. Bluetooth stereo can be controlled from my phone wirelessly. Has AM/FM for use in an emergency. Line in and USB too, if that is your bag. We floated the river for 5 or 6 hours and it kicked out the jams the whole time. Mine is on wheels so moving it is a snap.

A little off-topic but I always wondered how a transformer could change 60 Hz to 20 Hz in a telephone ring supply.
Finally found the answer:

So I went to Walmart and got some cheap 12 volt lawn care battery (I don't remember what it was for). I got a battery charger and just hooked it up, then hooked up the amp/subs without any head unit or speakers. I put a wire between the battery power and the remote so the amp thinks the "car" is on and I used a converter for auxiliary to the 3.5mm jack for my iPod.

It works. Problem is, especially after putting on a splitter so I could hook up speakers too, the subs only hit the extreme of lows. Probably because they are so low quality... but they weren't this bad in my car. I'm going to play with it tomorrow and try and see if I can figure something out.

quote Originally posted by Marvin McInnis: Also a good explanation. One detail correction, though. AC voltages are usually expressed as RMS voltage (average effective "heating" value) rather than peak voltage, but the DC output from the bridge rectifier will be the AC peak voltage (less two rectifier diode voltage drops ... ~1 volt each). For sine wave AC, the peak voltage will be ~1.4 (actually the square root of 2 = 1.414...) times the RMS voltage. Thus the DC output from a "12 volt RMS" transformer plus a bridge rectifier will be about 15 volts. Similarly, if you run standard power line 120 VAC through a bridge rectifier the DC output voltage will be ~168 volts.

Thanks for the correction. Like I said, my electronics courses were awhile back... Mid 90's, so refreshers are always welcome . I don't use what I learned everyday, but I still remember some of the stuff I don't use.

Edit: I just realised, all this time I thought I had you as a +. Sadly when I checked it was nuetral but that's been fixed now.

[This message has been edited by Khw (edited 08-22-2012).]

quote Originally posted by theBDub: It works. Problem is, especially after putting on a splitter so I could hook up speakers too, the subs only hit the extreme of lows. Probably because they are so low quality... but they weren't this bad in my car. I'm going to play with it tomorrow and try and see if I can figure something out.

Check the amp your using to power the subs. Look to see if the crossover is on and what it's set at if it is. Also look to see if it has a bass boost circuit and if so is it engaged? Another thing, car audio woofers and home audio woofers, while the dynamics of construction and function are the same, the parameters for the environment they operate in are different. So sometimes a car audio woofer sounds like crud outside of a car and a home audio woofer sounds like crud in a car. That isn't always the case though. I remember working at Radio Shack and we had our Mach 3 home speaker cabinets on sale. They had a 15" woofer in them with a adjustable mid and tweet. I had a guy come in wanting to buy one to use in his car... I explained it would not sound good. He didn't beleive me so I walked one out to his car and we hooked it up to his amp. The results were not good.