what is the reference of diy car audio?

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Hey guys,

My experience with diy audio is currently limited to home stereos, i modify amps/tuners/cd players and im building a chipamp.

Now, i am also buying a car in the next month, and i would love to diy my sound system. But, i have very little knowledge of car audio.

Where can i start learning about diy car audio?

some questions i would like answered are:

- to what extent are people diying (ie amp/ amp+crossovers/ sources/power supply, etc)?

- what is the reference in diy car audio (ie the equivalent of BrianGT's gainclone PCB boards for chipamps)?

- how do i build a system with quality sound reproduction as a priority and not window shattering bass as the goal?

- a list of all the parts/components i need to have a great sound system in my car (ie from the cd/tuner to the drivers and everything in between, what do i need exactly?)

thanks goes to the guy that has the courage to tackle this one :)
There are a few of us that are making our own amps, but the SMPS required to make a real audio amp work in a car is the hardest part.

I have designed and built several PSU's with varying degrees of success. I would say my last version works pretty well, but the PCB still needs some work. It uses 2 transformers at 75KHz for a total power capacity of about 1.5KW. This supply puts out regulated +/-40V and has been fairly reliable, but due to a few flaws in layout I blew some FET's during hard testing. The goal with such a massive supply is to be able to power all the amps with one supply - 4 channels (bi-amped stereo) plus 2 bridged for a sub.

That supply I will eventually post a schematic, PCB, and parts kit for so people CAN DIY car audio. I even have access to nice heatsinks for them to go in for a professional-looking assembly. The PCB size is 8" x 15".

Beyond DIY, a good sound system will be fairly expensive. If you could put a $$$ figure it would be much easier for me at least to make recomendations.

Thanks zagisrule,

i've been reading and trying to get an idea of the whole car audio world, and yeah, it seems the power supply is the hard part. i checked out project 89 on elliot's site (im sure u know this one) and it seems to hard for me to pull off at this stage.

if you could provide a kit for people to easily build an smps supply, im am sure it would be a tremendous success! i would be down for one for sure!

once i have a good supply, i could apply my chipamp knowledge to build the amp stage to my liking. but, ive been reading and class-d amps or tripath class-t amps seem like a very attractive alternative.

what class do you reccommend. i mean for me, building a chip based amp would be easy, is learning the was of class-d worth it for what im looking for (not volume, quality)?

how much would building an smps cost? if i go chip amp, i would like it to provide ~24VDC (and lots and lots of current ;)) will your supply do this?
Making a SMPS is rather pricey, a good-sized unit will cost $15-$25 for a transformer, $20 in caps, $20 in MOSFET's, $10 in other "stuff."

Development is the expensive part, you need to be ready to replace MOSFET's when you begin to really push some current draw.

I designed my stuff around a 12V supply, but there is no reason you could not run one off 24V as long as you add an 12-15V regulator for the control electronics. You could also push much higher rails with 24V, and lower current draw during normal play. I would just adjust the regulator feedback circuitry to compensate and keep similar rails and a lower current draw.

As far as actual amplifier topologies go, I am a big fan of the MOSFET used in a linear fashion. I have seen application notes of the newer class-D amps and I truely think that given a high enough carrier frequency there is no reason they could not sound excellent. I think for a sub there is no reason left to use linear amps except for the one that they are easy to make.

i think you misunderstood. i want to run my SMPS off a 12V battery, but i want my SMPS to provide 24VDC to my amp. that would be ideal rail voltage for LM4780 amp pushing into 4 ohm loads.

1500W is alot, i dont think i will be drawing half of that at max power. i was thinking 4x60W for mid/high + 2x60W bridged for sub. your price seems ok for the power supply, but if you supply a working kit, why would their be extra development costs? especially if im not pushing it that hard.

as for head units, are like 90% amplified? i dont want to pay for amplification in the head unit, if im just using the pre-amp outputs :mad:
what is an audiophile brand for a head unit? a brand/model that focuses on quality and not fancy eq's and screens?
24VDC single supply? Why do you want this?

It would be able to do that, yes, but it could also do anything from say +/-25VDC to +/-50VDC without any trouble.

The prices I listed would be for parts if YOU wanted to design your own SMPS. It is expensive to develop them because things need to be tuned. I only gave you that advice if you should choose to layout your own PCB and experiment with all the other factors involved as well.

The kit would be pretty much bombproof should I ever release them, and kit costs would be $100 at least...

As far as a good head goes, there are a few out that have no internal amp, Alpine and Clarion make some. I have heard things of Nakamichi and Eclipse but I have no experience with them. My deck is a Premier, sounds good to me but it does have an internal amp (I don't use it though :) ).

I couldn't really tell you hands-down who has the best deck. I saw a Denon unit once, and also a HK unit in a magazine, but as far as SQ goes, I am happy with mine...but I only have a mid-level system - no preamps, external x-overs, single alternator, no cabin quieting over stock, just good amps, speakers, and sub.



If you're looking for parts for a 12-24V DC-DC step-up power supply, try looking at almost any old AT or ATX power supply, 200W and above. The transformer core can be salvaged (Rewinding will be necessary) as can the BIG toroid output inductor and several smaller inductors. The PWM chip is usually a TL494 PWM ic (sometimes is marked KIA7500). The high-voltage transistors MAY be useful (check their Ic (or Id) rating), and possible the output diodes.

Most of the semiconductors (PWM Controller, MOSFETs, output rectifiers, etc.) needed to make an excellent quality 12V-based SMPS are available as samples from the major manufacturers (like National Semiconductor, OnSemi and others). Even the chipamps can be sampled from National.

As for how to design the SMPS, there are several books for this, and each has its strong pooints. Try Geo. Chryssis' book "High-Frequency Switching Power Supplies" (c) 1989; Abraham Pressman's "Switching Power Supply Design" (c) ??; and Marty Brown's SMPS Book (I forgot the title), available as part of the EDN series of design books.

Manufacturers of inductor and transformer cores (like Amodon Associated out of California, www.amidoncorp.com) have datasheets available for various EE, pot and toroid cores for a variety of materials (either ferrite or powdered-iron).

There are just a few ideas to get you started in the right direction in building your Amp. Hope these will help.

Steve :D
to zagisrule,

i would want ~24VDC to power about 6 channels, so each channel would need 24VDC to power my LM4780 based amps. these amps work better at lower rail voltages when driving 4 ohms. but the flexibility of your SMPS seems perfect. Any prediction when that would be ready?

to n-channel,

thanks for the leads, i was hoping to avoid building my own SMPS, i dont think im up to the task. do those books provide just general info, or do they have a step by step on how to convert a PC supply to what i want?

thanks guys.
I have seen 24V supplies and stuff for more commercial use I think to run equipment(radio or something). Should be easy enough to google but the ones I found the cost was prohibitive.

I emailed this company:
nightfire elec and hinted he should make one for car amps. Perhaps if he sees enough demand he'll do one.
I've been impressed with his products and pricing.
so i guess im waiting to find a kit for an SMPS... hurry zagisrule :D

on a different topic, car speakers. does one have to use speakers sold for car systems? these seem very overpriced in my opinion... can i just use regular drivers designed for home stereo use? is there an obvious difference im missing? how does one go about choosing speakers?
SMPS Books


Not exactly on the PC conversion, but they DO cover, in great detail, the step-by-step process of designing, building and testing all sorts of topologies (buck, boost, buck-boost, flyback, forward, half-bridge, full-bridge, center-tap push-pull, SEPIC, Cuk) and all sorts of control methods (PWM, quasi-resonant, resonant, ZVS, ZCS, Royer, etc.). Each stage is covered in great detail, de-mystifying the design and operation of switchers.

The section on transformers is especially revealing, as it covers just enough transformer theory for the designer's purpose, the different core materials (powdered-iron, ferrite) and geometries (EE-core, Pot, Toroid, etc.), and explains how and why the designer might choose a particular part. It then goes on to cover design and construction of a typical SMPS transformer, step-by-step, in a very cut-n-dried manner. I have used this design procedure for both 12V-based xfmrs as well as off-line xfmrs, with great success.

There's even a chapter in one of the books on Active PFC pre-regulation for the front-end of any SMPS. :smash:

As for using home 8-ohm drivers in place of overpriced car 4-ohm drivers, just remember because of the doubled impedance, the outout into the driver will be halved. So, if you're normally driving a 30W, 4-ohm amp into a 4-ohm driver, your maximum outout will be 30W. But if you drive into an 8-ohm driver, your maximum output will be only 15W, unless you bridge the amp's output to the driver. In that case, just double the rated power per channel, and that's the maximum power driver will see.

As for converting a pc power supply, it's just alot more economical salvage the parts, and DIY. You would have to make too many changes to BOTH the input side (from 115/230V input to +12V input), AND the output side (from +/-12V and +/-5V output to +/-30 to 35V output). Just use the transformer core, PWM chip and a few other components.

Hope this helps!

thanks, my school library has all the books you recommended! ill take them out as soon as i have some time.

as for 4 vs 8 ohm, thats not a problem, with an smps i could raise rail voltage and get the 60W per channel even into 8 ohm drivers.

i just hope i could place them properly to get some good imaging and SQ. any tips on that?

right now my vision is this:

-a nakamachi cd400 head unit which spits out 3 pairs of preamp outputs (2xfront, 2xback, and 2xsub... right?)

-an smps power supply driving a diy LM4780 based 6 channel amp. 4 independent channels putting out 60W each, and 2 bridged for 120W into a single sub.

-speakers: front- 2 mids crossed over to 2 tweeters
back- 2 mids + a sub hidden away somewhere

makes sense? :confused:
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