I would like to use car amp to push the home speaker.

How do you convert car amp's DC to AC power line for home use?

Thanks, if anyone knows how to do it.

You can buy a voltage convertor, but it will cost almost as much as simply buying a sub amp from Parts Express.

How much is it?

don't do it.you'll no doubt induce dc hum.
you can turn up the volume to overcome it but it will still be there

Why it will induce hum?

well, i think one is gonna be the ac to dc inverter although there are chokes available to filter this out probably a quality test bench power supply would have good clean power out this alone would probably be above the cost of a good home amp,and then another could be a "floating ground" i came across this on an amp in my truck,turned out to be a really stupid problem(little tear in the shield of my sub amp cable) but the term just makes me think that electronics like a good ground and i would think that intermixing different (car and home) would not be a good idea if any level of quality is to be maintained.although i do remember using the speaker level out on my sound-design receiver to feed a pyramid eq/booster(battery charger powered) to power 12" stromberg carlsen speakers 20 years ago.

car amps dont typically perform very well out of their environment for lots of reasons... youd be better off selling the car amp, and buying a cheapo receiver to do the amplification...

Never!! Receiver sucks!!

not quite as hard as a car amp sucks though.

I don't think it's worth it to hook up all the car stuff as a HT. A converter that could supply decent power and do it cleanly would cost too much. I've looked at doing this both ways before. However, I am curious as to what you have.

JT Clark-

If I have something, I probably would have told you already, man.

Actually it is just smart shopping. You can get very high powered car audio equipment in car parts shops for a mere fraction of what the thieving audio retailers would charge and that goes for both home and car audio retailers. Car audio has a different market dynamic than home audio because you can get off-brands for very low prices at non-traditional outlets like car parts stores. Ignoring this or pretending it is a bad idea is just acting the fool. Amplifiers are devices or circuits that increase the amplitude of the signal fed into them. The plain fact of the matter, is that the aim of every high fidelity amplifier designer is to create a product that has no effect whatsoever on the signal fed into it, other than to increase its amplitude and prepare it to be sent to a speaker.

Right now, I am seeking a cost effective solutions. I think the power input can be modified to accept AC power from wall outlet directly, but I am not sure if this can be done. Any experienced electricians around here know how to do this?

Tekdredger-

Thanks for the link!!

Smart shopping would tell you to get an amp from parts express (for example) and put the savings into the sub and its enclosure (or just save it). That would be a much better investment as the difference between amplifiers is much smaller than that of speakers.

Sorry I misunderstood your equipment. It sounded like you already had something. I only hear of this if someone already has their equipment and wants to get double use out of it. No need to get snippy.

Another possible way to go is a large 12V sealed lead acid (SLA) battery and a trickle charger. This method also has it's drawbacks. And NEVER use a regular car battery indoors! They release gasses that can be explosive!

If you don't yet have a car amp I'm not sure I would persue this project either. One of the reasons car stereo amps are cheaper is they don't use a big 120V mains transformer/power supply. It's just not electrically efficient nor cost effective to convert AC to 12VDC to supply an amp that converts the power again. And no, the amp can not be easily modified to accept the 120VAC directly. You see, inside the amp the 12V power coming in is fed to a converter circuit that pumps-up the voltage to something like +/-25V or more depending on the power rating on the amp. If you are really determined to do this the best way would be to build a bipolar DC power supply so you could bypass the DC-DC converter and feed the amplifier circuits directly. This would give you a circuit architecture most like a typical home amplifier. But this would be a pretty advanced DIY project and if you aren't up to the task yourself getting someone else to build it for you shoots the budget again.

Using a bench power supply like I linked for you will work and is probably the cheapest (but not really cheap) way to go. Car amps draw tremendous amounts of current and you have to use a very large unit so you don't strangle the amplifier.

So like I said, unless you already have something you are trying to utilize I wouldn't go out and buy anything to go in this direction. You would be better off looking for a used amp designed for home use.

Yes, I certainly know this. However, I have too much drivers need to power up and I am running out of amps right now. That’s why I need some cheap alternatives. Hope you understand.

I didn’t get snippy with you. I am just little tired of hearing someone who says car amps don’t perform well in certain environment for loads of reasons and not listing any of them to support his claim.

Tekdredger-

If I have a 400 W amp, how many amperes do I need for the power supply? Thanks for the info.

if you plan on pursuing the car amp thing,then on the amp you intend to use, check the fuse rating on the amp itself, that will tell you the max amperage you will need. if for some reason the amp is not idiot proof(no fuse) check the manual or web site for the specs.if you plan on running multi-amps add the value together,but if you can isolate the power supply (no hum) then you still need to follow car audio rules,caps heavy gauge power and ground wire, don't forget a remote wire which you may or may not have to rig yourself because you won't have a car stereo to trigger and i don't even know if a power supply would have one and i also don't know if a home stereo trigger would work.i just would not do this whole project.but it's a hobby to most,addiction to others.have fun, hope you don't damage anything.by the way the dry cell battery could work but if you have the trickle charger on while playing...dc hum.........

So you DO have an amp already? What brand and model? This would help determine current needs since just the power rating can be deceiving.

damn a $100 car amp delivering 1000wts is just what i need. why didnt i think of that idea?... why hasnt everyone else?

wow,my 900(rms) watt alpine cost over $700!
for my truck,stays in my truck!
hook a brother up curegeorg.

oh, i was LOOKING for one to run all my gear from. do you think i could use a car amp as a backup generator for the house? i could probably run the whole neighborhood if i wired it up correctly.

Oh, you have the amp already? We're trying to help, but we need information. What we're given seems to be confilcting.

400 watts RMS? A converter should be able to do it for one of these amps. 400/120 = 3.33 amps. At full power it might draw more like 5 and put out 3.33 due to the inefficiencies inherent in the conversion. I don't remember off the top of my head who makes better models as I did more research in the other direction.

Quick look , 540 watts @ 4 ohms for $250? No conversion, so no worry about blips in the power supplied. BTW, what sub(s) will this be for? That'll help. I'm curious as to what amp this one is too.

if i remember right,i have heard nothing 'bout subs.sounds like you want to power mains/surrounds..........but please reconsider!!!
car....====car......home.....===home

come on,gong....soundhound,we have lots of respect for opinions.....

no support is needed, it is a consensus that car amps in the home are "not the best idea" (to put it liberally). there are things in this world that you sometimes have to accept without explicit proof. we are lucky to have had people smart enough for us to trust, but then again, in a thousand years someone might think Einstein was an idiot...

Sorry about the late response.

Painttoad-
Thanks for the info. That was very helpful.

Tekdredger-
No, I don't have one yet. Right now, I am using several QSC RMX amps and Selenium pro drivers in tri-amp mode with some duplicated channels. Would you like to recommend some nice models? I only need some 200W per channel stereo amp.

I also have a question. I am not sure if you know it or not. I went to a local car shop today (Similar to electronic store that kind of car audio demo room) to check some amps and found they were able to power up several of those amplifiers in their demo room instead of cars. How did they do that? Where did they connect their power? Are they also using the power supply? Let me know what you think. Thanks.

JT Clark-
Thanks for the sub amp recommendation. But I need an amp that will do 20HZ~20K so I can use it for mid-woofer and tweeter also. Thanks anyway.

That's your fu***ng consensus, not mine; and I don't give a shit. Get out of here if you are not interested in this subject. No need to post some depressive, meaningless messages around here. I simply don't want to read.

come on now, let's not be that way.they have this forum for US. let's not abuse it with language.and we all know curegeorg is going to put his 2 cents in no matter what.i too think this project is a waste i'll say what i can to keep you from doing it but i'll not slam you. the stereo shop would have a good regulated power supply.why not ask them what they paid for it.the response may send you to a home theater store(where i'm sure a lot of people think you should be)

sorry about the "gong" thing GONK

I've stayed out of this debate because the sum total of my experience with car amps is a few friends who have installed amps and aftermarket speakers in their cars. Clearly things have gotten a bit heated here, though, so I'd like to try to offer a few comments.

First, it is technically feasible to power a car amp from 120V AC power. Tekdredger sounds like he has some good insight into the mechanics of this, and you might also get a few leads from the way a custom car audio place does their in-store demos. Doing so will likely pose some challenges, but depending on the goal of the project that may be part of the appeal.

Second, there are likely some inherent differences between the home theater and car audio markets, if for no other reason than the differing power sources and space considerations involved in the two markets. I think those differences need to be focused on before we decide if this project holds promise or not - the "explicit proof" that curegeorg alludes to as not being available. It does appear to be true from glancing at a few online sources (including Parts Express, since that site's already come up here) that the cost per watt range for car audio starts lower than for home theater. For car amps rated at 50W to 125W per channel (4 ohm loads typically), prices seem to start around $0.70 to $0.80 per watt, although you could certainly move up to amps costing $1.50 or $2.00 per watt if you chose to. Any of these costs will then need to be increased to account for the expense of converting from 120V AC to 12V DC to power them in a home setting, of course. This could be compared to Outlaw amps (since we're here) - using 8ohm ratings, the M200 sells for $1.50 per watt while the 7100, 755, and 770 all go for $1.29 to $1.30 per watt. If we keep things "apples to apples", however, and look at the 4ohm ratings for those amps the cost per watt drops to $1.00 for the M200, $0.87 for the 755, $0.86 for the 770, and only $0.78 for the 7100. However you look at it, these prices paint part of a picture. The other part (which I don't know about) lies inside the amps themselves - they all do the same basic thing, amplifying a signal, but are there differences in how it is done? What is the signal-to-noise ratio in a good car amp, as compared to a home theater amp? What sort of THD do you see? What impact does the added power supply issue generate? These are the questions that have not been answered here yet. I don't have the answers, unfortunately. I do understand theendofday's reluctance to discard his plan without getting those answers, and I can see how simply saying "don't do it" without at least some explanation is insufficient for him. Even though I have no plans to try this, I'd like to hear some more concrete explanation myself.

Third, we may need to also address the quality of the amps (as pertains to their intended environment) in this debate. If we are talking about a cheap "bargain" car amp that might be considered the automotive equivalent of an entry-level receiver's amp section, then going through the process of building a power supply is likely at intellectual exercise at best - the results should be no better than simply using one of those entry-level receivers. If we are talking about a good car amp, then the cost and effort involved in building a clean and quiet power supply may be the only barrier - but the audio results may be no better and the overall cost even higher than going with a good, economical home theater amp (either an Outlaw amp or even something used off Audiogon).

I guess at the end of the day, I would prefer to get a good amp purpose-built for the home theater environment rather than taking a car amp (hopefully also a good amp for its market) and trying to transplant it into a home system. On the other hand, I have this weird vision of a mysterious power supply tucked away out of sight and a field of surface-mounted car amps mounted across the front wall of a home theater...

i know that you can hook up car audio in the home and make it sound decent.that is a CAR AUDIO complete system.i have no idea what will happen with home pre-outs driving a car amp(s).i think the x-over from home theater to car theater is getting a bit out of hand.when i'm in my truck i wanna jam not watch a movie.(but that's a different subject)
just remember car audio amps require large amounts of current and if the power supply you buy or make can't cut it then the music turns to mush,then choppy,then quits,then the click of the circuit breaker.....(on the power supply)
i'm gonna head out and talk to my buddy and see what he used on the demo board in his old shop,maybe i can come up with the model of something of good clean power for you.
i have a decent knowledge of car audio , a good grasp of home audio but i just don't know if you will achieve what you are after.
i'll help if i can.
i'd like to see this thread continue,i'm sure even though some of us are against the project, i think we are all curious

It can work, but the conversion gets messy. You're going from AC to DC with the converter and then back to AC in the amp. There are a number of car amps that can have some EXCELLENT quality to them, and there are a lot that are absolute garbage. These will have ratings that many of us that are into car audio call "When lighting strikes" meaning they will only make that much power if lighting strikes. This is not the only value that manufacturers might fudge either. I'd have to know what this amp is to be able to tell if it is good or not, but rest assured that car audio amps can be quite good.

With the RCA signal, I think it should be ok as car amps are adjustable and all of them can take from under 1V to several volts of signal strength, depending on the model. The low end tends to be from say 0.2-0.5 V to a higher end of 2.5V-15V. There is no way to correlate better quality to voltage ratings. I know of good amps that are on both ends of that.

I've looked into power inverters more which switch DC power to AC. Those will run from a couple hundred to $600-700 or so depending on how stable you need the power to be and how much power you need. The power converter might be cheaper than that, iirc, but you're not going to pick up a new one of anything approaching decent quality for like $30-40.

Now for the converter output amperage, you will need around 30 amps of output to be able to play 400 watts, depending on the output voltage. If it's an AB amp, then double that value (60 amps)as AB amps are about 50% efficient. If it's class D then figure around 43 amps as they are about 70% efficient on average. Since it's for mids and highs, then the first one sounds more accurate as next to all of those are AB amps.

I can't give any recommendations as to which power converter to use as I just don't know. theendofday can use Google just as well as I can (I would hope ) to find a place that sells them. Maybe link them back here and see if anyone finds something suspicious. You want to go from AC power (the wall socket) to DC power (what the amps takes). When searching, don't confuse this with a power inverter which goes from DC to AC. It wouldn't hurt a local audio shop what they use in there demo boards as it should be of appropriate size for what you want, especially if you've dealt with them before. The worst they'll do is not tell you.

checked out the power supply,here is what my buddy used to do(he informed me that alot of shops do this) 3 OPTIMA YELLOW TOP(I RUN 2 IN MY TRUCK) IN PARALLEL.
charge them when not in use, do not use marine batteries as their discharge is a bit slower than the optimas.the yellow tops are car audio batteries they will run around $150 each.
this is probably the only way to get the current you are gonna need without spending(i've been told) at least $1000 for a stable,clean 100 amp power supply
to let you know, 2 optimas,2 1 farad caps,4-12's(in the cab),jbl component speakers,3 alpine amps(1507 in mono) for subs,i hit 151.2db in my s-10,took second in the shootout to a station wagon with 8-12's that only hit 152.4.man was i mad

I have a question about the AC to DC power supply. Why the toroidal transformer typically used in home amps (or all the AC amps) draws only a little bit of amperages from the wall outlet compared to the car amps for the same power output of 400 W? What is the difference? Is it possible to buy a raw toroidal transformer for very cheap and connect it into the car amps?

For example, my QSC 850 amps only draw about 5 amperages for the 4 ohm 600 W output. How can I achieve this with the car amp?

I am sorry if this may seems stupid. But, I want to know more about amplifier technology.

It all goes back to the interaction between amps, watts, and volts - and in this case, it's the volts that makes all the difference. A home theater amp operates on the 120V power available at the outlet (at least as far as the US is concerned - Europe does things a little differently). Since watts of power are related to volts X amps, an amp supplied with 120V will draw approximately 1/10th the amperage of an amp operating from 12V.

I would also like to know more about the toroidal transformer conversion from AC to DC? Why many people use it to convert power?

Also, is there anyway to modify 12V input to 120VAC?

How about DC bi-polar project?

From what I understand, car audio amps are designed to operate from a 12VDC power supply, which is why painttoad's buddy suggests driving amps with a bank of batteries (which provide DC power rather than AC). I did a little googling to try to find a little more info on exactly what all has to happen in a home theater amp, in order to help confirm some assumptions I was starting out with. First, there's the transformer, which is stepping the voltage down to a more manageable level. The output of this transformer is still going to be AC, though, so the car amp wouldn't be able to connect to it. You would still need a rectifier to provide DV voltage from the AC source. There are also some capacitors tucked in after the rectifier. The capacitors may be part of the car amps, but the transformer and rectifier are not - and the copper wire windings in a good transformer alone likely account for a significant portion of the difference in cost between car and home amps.

I guess the bottom line is that a big beefy transformer alone cannot allow a car amp to be plugged into a 120V wall outlet. The power supply package required to do this can be scratch built by someone with some electrical know-how, but it's not likely to be a straightforward process. The simplest route from an installation standpoint certainly sounds like it is to borrow the car audio shop approach of banks of 12V batteries that you charge when not using the system, but there's a hassle factor there. Having seen the code-mandated ventilation requirements for commercial buildings with lead-acid battery banks located inside, I also wonder about what hazards (both fire and health) might be involved in bringing a group of such batteries into the living room on a permanent basis. As tekdredger noted earlier in the thread, these batteries can produce noxious gases. Building a power supply that outputs clean 12V DC would be the surest and most convenient way to drive a car amp from house power, but there are two factors that make me tend to recommend against it for anything except experimentation. First, the cost involved in buying or building such a power supply is going to probably wipe out the money saved from buying the car amp. Second, when you buy a home theater amp you are getting a power supply section designed by an electrical engineer specifically to power that amp, with a myriad of design decisions that you and I may not have any idea about - if we try to duplicate that design effort for a power supply to drive a car amp, the end result is likely to not be as good, and that could yield a system that colors or distorts the signal being sent to the speaker.

Looks like we were writing our posts at the same time. I think I've partially answered your questions already, but want to add a little summary.

The transformer does not convert from AC to DC, but instead changes the voltage. A transformer of some sort is necessary in order to get the voltages involved down to a level that speakers can cope with. I believe that toroidal transformers are most often used in home theater amps because they are the most effective way to pack a transformer large enough to handle the required current - although most receivers elect to use a "square" transformer (technical term there...) that looks like a scaled down version of what you might see sitting behind a building to save space inside the cabinet.

All speaker amps are working with DC power at some voltage when it comes down to actually driving the speaker, so the amplification section itself cannot directly accept AC power. The only way to change the amp's power input from 12VDC to 120VAC is to build the sort of power supply (transformer / rectifier / capacitors) that home theater amps use - thereby producing DC power that the car amp's existing power input can accept.

Sorry, no clue.

the optima batteries are sealed,dry cell
and make a big difference in the sound in a car.
if anybody dabbles in multi amp car systems, then i highly recommend them,
there is a lot of reserve there,sorry to plug optima in this forum but we know who makes some of the best(if not the best value,with quality in mind) home theater products so i think everybody should know that on the same lines they are the best for car audio batteries

Gonk, thanks for the info.

Painttoad-

Is this what you are talking about?

http://www.1st-optima-batteries.com/

Tekdredger-

I am interested to know more about DC bi-polar supply project or any great idea about modification if anyone knows.

d34/78
yep that's them
make sure you get the yellow top which is "D" series ask for it by name or you may get a red top

Man, that is too awesome.

I am checking it out. They say it can run 50 hours? True?

I can chain them in parellel for more electricity, right?

not more "electricity" so to speak
you'll still not have more than 12 volts but the reserve will be there

Found this at Optima's site regarding battery runtime and "amp hours":

The D34/78 is rated for 55 amp hours and 120 reserve minutes, so one battery will yield 2.75A steadily for 20 hours (55 amp hours divided by 20) before reaching 10.5V and being classified as "fully discharged." It will carry a 25 amp load for two hours before needing to be recharged.

It's been a while since I messed with electrical circuits, but they are similar enough to pumps that I can keep up somewhat... Adding batteries in parallel would provide more amps at the same voltage, right?

i think you are right gonk(i'm not gonna pretend to "know something" if i'm not sure)
but i'm doing it all for reserve in my truck i have an 160 amp alternator that cannot power the truck and stereo so, basically they provide the ooooooommmph for a peak (reserve)i was sold on my amps because the are "unregulated" whereas if you can put more in you get more out (to a limit of course)

it's amazing gonk, i'm talking about 160 amps here and you are on another thread talking about 15 amps!
how can there be such a difference between the home and car power requirements.
this is a good question if somebody really knows(and don't say cabin gain 'cuz if there is such a thing then why do i have to have 4 times as much in my truck compared to home in something 1/20 of the size)???

In the case that theendofday is considering, there is not an alternator available to provide that baseline 160amp flow (unless he runs power in from his car and leaves the engine running), so he would be using the batteries in parallel to produce all of the current for the system. If we take a trio of batteries in parallel, that would be either an 8.25 amp load for 20 hours (which wouldn't offer much) or up to 75 amps for only two hours. For brief demos in a store, that would probably be pretty effective - running at a very low level for most of the day with brief spikes up to a very high level would probably not drain the batteries until near the end of the day. For use in a 5.1 channel home theater, it may be fine for prolonged two-channel listening or watching TV at moderate volumes, but you may also find yourself stopping at the end of the first disc of the extended edition of Return of the King to recharge batteries before continuing with the second disc.

i spoke too soon,i went out to have a smoke and started thinkin' DC and with the wattage and current ratings out of my home amp it kinda collaborates with my car amps

You're looking at amps at two different voltages. We're looking at 15A when it comes in at 120V, but with home theater equipment we don't really track how many amps may be zipping around downstream of the transformer or really even what voltage it's at (although the equipment's designers certainly do). In a car, you don't have 120V, you have 12V, so to achieve the same power (watts) you have to increase the current (amps) by a factor of 10.

Think about it this way - your 160A alternator is operating at 12V, while the outlet behind your entertainment center is connected to a 15A circuit breaker and is operating at 120V. The two are capable of providing roughly the same wattage - 1800W for the outlet inside, or 1920W in the car.

ok that helps!

gonk, good explanations. This topic has really gotten going here.

Do you guys seriously think he should use the batteries? How is he going to recharge them? I thought this setup was supposed to be an HT setup. Meaning he should be able to just plug it in and only have to turn it on and off, basically. Besides the tweaking of the settings he'll need to do I mean.

i think if he pursues this it's gonna be one hefty project,and be far from plug and play
i wanna see it

Paralleled batteries will give you increased current capability - at the same voltage.

Jeff Mackwood

ps. While this sounds like an interesting "what if" project, I still don't understand its inherent advantages (if any) over using an amp designed for home use. If the real driver is cost, then I'd suggest picking up some good used amps (like NADs, Carvers, etc.) off eBay - likely for less than the cost of all the bits and pieces you'll need to buy to use car amps - and with better sounding results. I've acquired five different stereo power amps that way.

ps. I remain highly skeptical of the claimed power output ratings (and other specs) for most car amps. I have a hard time equating 1 claimed car amp Watt with 1 claimed home amp Watt.

i'm glad you said "most" i agree there(ratings on most car products are a joke) but i don't doubt the power in my truck. i would much rather sit here and listen to my home system not my truck sytem in my home

Some years ago I used a 2 channel Kenwood 12volt DC car amp bridged to put out 150watts rms to power a sealed 12inch sub. I used a 12volt DC crossover to feed the signal into the amp so that I was only amplifying the sub frequencies. All of this was powered by a RadioShack AC to DC converter that weighed about 20 lbs and cost about a hundred dollars. The crossover had a remote gain control that I adjust from my seat. All this was gear was placed behind furniture to be out of site. It was visually unappealing. It did not sound too bad, performance was more dependent on sub room placement than any thing else.

You would first need to know some more specific information about the amp you intend to modify. Specifically, the circuit configuration and the rail voltages and the current demands need to be understood. Then the power supply would have to be designed to meet those same requirements. Here's a pretty good tutorial with some insight into power supply design for audio power amps. To actually modify the car amp the DC-DC converter would have to be disconnected or removed and replaced with the newly built supply.

Tekdredger-

Thank you very much!! This is just what I need to understand. Is there anyway to know about amp’s circuit configuration and the rail voltages and the current demands? Is it possible to know these parameters with some testing equipment? I probably need some books or experienced technician to guide me through this project. But, I think this will be a fun project. Audio is interesting isn’t it? And that’s why I love to try different things.

By the way, have you ever done this kind of project before on your own?

Thanks again.

tek, i was getting into that link before i got company,i'll get back to it later.this site is so useful.glad to see the topic starter back

It's been a very interesting (and lengthy!) discussion and a fun subject. Battery power for car amps in a home theater seems most likely way to get the best sonic performance out of car amps, but the cost of the batteries and a battery charger will negate any savings in buying car amps over home theater amps and you'll have to deal with the hassle of shutting the system down and recharging the batteries (with the duration between charges dependent on the number of amps and number of batteries). You would need at least three or possibly four of the batteries that painttoad suggested (at close to $150 a pop) plus charger(s) to yield enough power for a few hours of intense home theater use. That's a lot of cost and a lot of hassle - a Model 7100 would be cheaper than batteries, charger(s), and amps to provide comparable power.

A power converter of some sort is a much more user-oriented solution to operating a car amp on 120VAC power, but again you are looking at incurring a healthy cost. I stumbled across tekdredger's very nice tutorial link earlier today while looking for information on amp power supplies, and it does seem to be a very good insight into the power side of amp design. It also looks like a great deal of work and cost when home theater amp makers have already done the work and tucked it into a metal box.

As far as car amps versus home theater amps in general, I've noted at least a few clear differences. Car amps are routinely rated at 4 ohms, whereas home theater amps are usually rated at 8 ohms (sometimes 6) - this makes the car amps seem a good bit more powerful dollar-for-dollar, but in a home theater system that routinely has 6 ohm and 8 ohm speakers you'll have to adjust car amp power ratings downward accordingly. Also, there should be a cost difference watt-for-watt between the two: home theater amps are saddled with a large transformer (crammed full of expensive copper wire) and rectifier required to produce DC power. Taking into account the cost of such a power supply and the differences in power rating, you can get a good home theater amp from several respectable manufacturers (including Outlaw) for comparable or less money than required to buy car amps and arrange for power supplies or batteries.

I would not want to pursue the project and I don't know that it can be done for less money than a home theater amp, but it would be a very interesting sight to see if somebody went through with it.

i've liked this post , i don't think it's feasible but has kept me going.
gonk, i had a pair of 4x6 2-ways,that were rated at 3 ohms to "coax more power from the amp"

Tekdredger-

What are the materials I need to prepare for the new power supply?

Thanks

Yes, Painttoad. You can also use parallel or series driver chaining to form any ohm you want. The load on the amp is really not an issue. As long as you know what you are doing.

yeah,i understand,i'm series parallel on my subs.
i just thought it was funny the way it was stated,they weren't bad or cheap for what they were .

but i do think the load on the amp is an issue.
for whatever reason our more electronically inclined outlaws can give us i think the easier an amp can work (load) the better it can perform it's job.car or home!

The best place to start would be with any information the amp manufacturer can provide, especially schematics. A repair manual, if the manufacturer even prints one, is ideal since they usually include a pictorial diagram of the circuit layout, the schematic drawings and parts lists. Sometimes they even include a little circuit theory as far as the design being used. If the manufacturer isn't cooperative in releasing this kind of info, and many times they aren't, if you are friendly with a dealer they may let you have a peek at a drawing or two. Yeah a simple voltmeter can measure rail voltages and some algebra will get you in the ball park but there is nothing better than knowing just what the original designer had in mind.

While I have been building and modifying equipment for quite a few years, no, I haven't done anything exactly like this. This wouldn't be a real exotic project but I am a little concerned about the sheer size of the power supply (electrically speaking) for a first time DIY project. It is usually better to start with something a little smaller. Power supplies of this size can put you on your backside (or worse) if you aren't careful. You may want to hit the library first for a few books on basic electronics as well as power supply design. Here's a link to a DIY audio forum where you might lurk around or post a few questions as well.

I'm heading out of town for the holiday weekend shortly so I won't be checking this thread again until Sunday night or Monday. Have a Happy Thanksgiving everyone!

lots of posting on this topic today...

it is a waste of your time converting a car amp over to home use, but it is your time, so waste it.

it is not nearly as complicated as you seem to be thinking it is. they make ac to dc power converters, you just have to find one that outputs 14.4v. though i think they are expensive...

the performance of car amplifiers is far inferior to home amplifiers in regards to quality, low distortion wattage. car amps are made for different circumstances and with different goals in mind. their application to home use, while feasible, is impratical.

if you are attempting this project for your own interest, then have fun. if you are doing this as a permanent solution, then you are off your rocker.

either way, good luck with it, and have a good thanksgiving everyone. i dont really have anything else to say about this, but there was no need to be rude in your post re: my statement endoftheday.

good turkey day all!!!!

A power transformer that has a 120VAC rms primary and a secondary voltage of about 11.3VAC rms (about, to allow for two diode voltage drops), a diode bridge rated to handle tens of amps of currnet and some large electrolytic and film filter capacitors will make a basic 14.4VDC power supply. A power switch, fuse, and indicator light for the primary of the transformer would be nice also. A safe case, with venitlation, would be nice, too.

Beings this basic supply is not regulated (a suitable regulator circuit will add a lot to the cost), significant ripple voltage will exist on the DC voltage. This ripple voltage will increase as the load on the supply increases (playing the amp and speakers louder).

In order for this ripple voltage to not be heard as a hum in the speakers, the amp's DC-to-DC converter (to generate the higher DC voltage(s) that the amp circuit itself needs) needs to have a good (high) power supply rejection ratio (PSRR), which is the circuit's ability to reject variations in the input 14.4VDC and just do it's job. The amp itself should have a high PSRR, and probably will if it is a high feedback design.

Paul

Hello Paul

Will this transformer work for the 100 amperes DC power supply?

It shows second voltage 30V+30V. What does it mean?

Where can I buy diode bridge and large electrolytic, film filter capacitors?

Thanks

well, there you have it ,looks like you're on your way.keep us posted,i'll follow and throw my 2 cents in when needed.
good luck!

OK, I looked at the web page for that transformer.

"It shows second voltage 30V+30V. What does it mean?"

This means that there are two secondary windings, each putting out 30VAC rms when the primary windings, of which there are two, are connected to 115VAC rms.

In your case, 30VAC is way too much. WAY too much as in fry your helpless car ams big time.

If you connect the primary windings in series (and the secondary windings in parallel) observing the proper polarities, then the secondary voltage will be 15VAC rms. This is still too much. This would give about 20VDC to the car amp. Poof!

I think one of the other transformers that have secondary voltage ratings of 25v, will be more suitable. If their primary windings are connected in series, then the secondary voltage will be 12.5VAC rms. Allowing for two diode drops due to the bridge rectifier, the DC voltage will be in the neighborhood of 16VDC. This may be too high for your amp, maybe not. It depends on what your car amp is rated for in regards to maximum voltage.

Parts Exprss also had diode bridges, but the highest current rating (continuous) was 25 amps, but I would want at least twice this. Other supply houses, such as Mouser or DigiKey may have higher rated ones.

As far as electrolytic caps, you could use the same cap that is offered for use in car amp installations. If you have a car cap, use it, otherwise, just bring $$$. Mouser or DigiKey (or Newark Electronics, or Allied Electroncs, or ...) would also have these. 20V 100,000UF would be a good starting point as far as capacitor value goes.

Paul

OK, Paul. Let’s take this imaginary 2 channel amp for example. It has this specification.

It needs a 13.8V power supply.
It outputs 500W total into 4-ohm load. (250W per channel)
It consumes a maximum current of 90 amperes.

How can I determine the type of transformer I need based on this 3 specification. (How many VAC for primary winding and how many VAC for secondary winding)

Also what about the VA? 500VA, 800VA, 1000VA, so many kinds. How to determine the value I need based on the above 3 spec.

When parallel or series those windings, should I solder them together? Or I can just tie those cable together?

The diode bridge also called rectifier, is that correct? Or are the two different things.

How much money do raw electrolytic caps usually cost? I found ready-made car caps are not cheap.

Also, what will happen if the caps UF value is really high? Like, 900,000 UF. Is that value higher the better?

Thanks, Paul. I am the beginner and need some professional guidance. Hope you have patience.

"OK, Paul. Let’s take this imaginary 2 channel amp for example. It has this specification."

If you have an imaginary 2 channel amp, then you can build a killer imaginary power supply for it for nothing.

"It needs a 13.8V power supply.
It outputs 500W total into 4-ohm load. (250W per channel)
It consumes a maximum current of 90 amperes."

The 13.8V rating is a nominal value. There should be a maximum voltage specified. Maybe the manufacturer has this spec. on their web site.

13.8V @ 90A max means 1242Watts of power (max) consumed. This will give you some idea of the power requirement of the transformer. Wttts and VA are somewhat similar (but not identical). Watts is a special case of VA (Volt-Amps) which involves trigonometry.

"How can I determine the type of transformer I need based on this 3 specification. (How many VAC for primary winding and how many VAC for secondary winding)"

If you are plugging in the transrormer into the wall outlet, you are giving it 120VAC (about).

What you need OUT of the transformer is about 11.3VAC, as I stated in my first post to this thread, with further elaboration in my second post. As the amp puts out more power, the voltage out of the transformer will decrease. A transformer rated at higher VA will do this less than one rated at lower VA. When the amp is putting out nothing, the transformer will be putting out a higher voltage. You must make certain that, when this transfomer voltage is rectified and converted to DC, that this DC voltage is NOT too high for your amp. Or else fried amp. You should find out what MAX voltage you amp is rated at.

Too much voltage: fried amp.

Too little: you don't get the full rated power out of the amp or it doesn't funcion properly (in an extreme case).

"Also what about the VA? 500VA, 800VA, 1000VA, so many kinds. How to determine the value I need based on the above 3 spec."

1242Watts of power (max) should give you a clue.

"When parallel or series those windings, should I solder them together? Or I can just tie those cable together?"

Solder is best.

It depends on the particular transformer and your needs.

As in the case of the transformer that had two primary windings, each rated at 120VAC and two secondary windings each rated at 25VAC each, the 25VAC is way too much. Beings there are two primariy windings, the user has some added options. Connect the two primary windings in parallel (the proper way, noting polarity of the windings) to get 25VAC out of the secondaries. Connect the windings in series to get 12.5VAC out of the secondaries. The secondaries would then be connected to each other in parallel so that you would get 12.5VAC with about twice the current of each secondary by itself.

"The diode bridge also called rectifier, is that correct? Or are the two different things."

A bridge rectifier (for single phase use in this application) has four rectifier diodes in it. One of these type of diodes, by itself in it's own package is sometimes called a rectifier.

It would be best (and more expensive) to get a bridge rectifier rated at 90A or more. These things have a "surge" or "peak" current rating that is a lot higher than the "steady state" current rating, so a bridge rated at 50A may be OK. Four rectifier diodes can be hooked up to funcion as a rectifier bridge. Note that the rectifier circuit (bridge or 4 diodes) will be dissipating some power (90A max times about 1.6V gives about 144 Watts max). The average power dissipated will be much less. So, a heat sink is a good idea.

"How much money do raw electrolytic caps usually cost? I found ready-made car caps are not cheap."

Yes, they are not cheap, especially if you buy them one at a time. Depanding on the capacitance and voltage rating, anywhere from $5 to over $100.

I'd look at surplus electronics places and see what I could find on sale. If I had to parallel a bunch of 20V 10,000UF capacitors, I'd condider that if the price per capacitor was low enough.

You do not need a cap rated at more than 20V, so don't waste your money on higher voltage caps (unless you get a really good deal). Also, a bunch of 10,000UF to 50,000UF caps in parallel may be less expensive than one big cap. There are other benefits of using a bunch of smaller caps as well.

"Also, what will happen if the caps UF value is really high? Like, 900,000 UF. Is that value higher the better?"

The higher the better, up to a point. The more capacitance, the lower the ripple voltage on the DC voltage and the more steady the DC voltage when the amp is putting out a large burst signal.

But, the higher the capacitance, the higher the peak current through the rectifier diodes and transformer. So, very large capacitance values can give problems, too.

In addition, when first turning on the power supply, there is a huge surge current as the capacitors first charge up. More capacitance makes this worse. Some amps have a resistor in series somewhere in the power supply ciruit to limit this startup current. When the caps get charged up enough, a relay kicks in to bypass the resistor.

If you have to pay list price for every item (switch, fuseholder, fuse, transformer, indicator lamp(s), rectifier bridge or diodes, maybe a heatsink for the rectifier, capacitors, chassis, and other misc. parts) you may find that an amp for home use may be a better option. Buying electronics parts one piece at a time is expensive.

Paul

Also, is this really a project that should be undertaken by someone who has to be taught basically the entire theory?

This would be a project suitable for someone who HAS had a basic electronics/electricity course (assuming he/she actually learned the material).

For someone who does not understand the basics, one should have a mentor. Otherwise, building this sort of power supply by trial and error could be very expensive and dangerous.

Paul

lol, i agree.

It would be easier to just build a 120 volt amp from scratch!

i would agree with hullguy!
do they still make kits like the old HEATHKIT tube amps of yesteryear?

The Heathkit company is still around. The Heathkit Virtual Museum has some good information. The kits are no longer made.

so whats the story with this project?