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Old 19th March 2007, 17:55   #1
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Default planning to build car sub amp, help needed

hi guys,

was thinking of building a car sub amp myself. want to know if anyone knows where to source parts from in india and what kind of amp i should build? i have no experience so please suggest if i should go for it or not? i love diy thats why this thread. vivek, navin??

navin can i have the specs of your diy car amp which you are using in your octy?

thanks guys
rishabh
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Old 19th March 2007, 18:17   #2
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which sub are you going to drive....or what power requirment range do u plan to achive.....
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Old 20th March 2007, 02:09   #3
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hi lbm,

im gonna drive my hertz es380 15 incher. im looking for around 400 rms. have you diyed an amp?? would love to share the knowladge. i love diy. seriously can a noob like me build an amp? well i dont care if i fail but i really want to try and succeede. i can buy a good monobloc for my sub but phaji diy is the thing for me. so please help me build my first amp

thanks
rishabh

are you low bass makker or low bhains makker lol...kidding
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Old 20th March 2007, 10:24   #4
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Quote:
Originally Posted by clipto333 View Post
im gonna drive my hertz es380 15 incher. im looking for around 400 rms. have you diyed an amp??
I have DIYed an amp. It was many moons ago. It used Hitachi 2SK135 and 2SJ50 MOSFETS (I hope I have these numbers right becuase my memory is not very good today).

Now this was a time when cheap amps like Sony 554 and Pio 6100 were just not available in India. BTW I also had DIYed a CD player (1985) and before that a cassette deck (1978) for the car.

As a noobie I would start with a kit. There are many from EFY that work well. I have not been happy with Elektor kits and they are often buggy but as my Dad used to say you learn more form buggy kits and you have to debug them than from stuff that works on the first go.

Lastly, please use the public forum instead of PM. This way many others can participate.
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Old 20th March 2007, 14:47   #5
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Quote:
Originally Posted by navin View Post
As a noobie I would start with a kit. There are many from EFY that work well. I have not been happy with Elektor kits and they are often buggy but as my Dad used to say you learn more form buggy kits and you have to debug them than from stuff that works on the first go.

Lastly, please use the public forum instead of PM. This way many others can participate.
hi navin,

thanks for your reply. will see if i can procure a kit amp. will post my progress.

keep the suggestions flowing in people.

thanks
rishabh
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Old 20th March 2007, 15:23   #6
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Isnt it better to build a pre amp using OP AMps and an AMP to be put after the pre amp.
Clipto : Here you go
Audio Amplifiers
Amplifier Circuits - Audio Amp Schematics, Page 1 - free electronic circuits - Links
Audio Amplifier Circuit Design

A word of advice though. I made quite a few amps during my engg days, experimenting with textbook circuits and trying to push to the limits. The biggest enemy I found was oscillations when I was pushing too hard and/or noise.
OP-AMP powered amps were better with less noise and better stability, but I think the main factor was that the quality of op-amps in our lab was much better than the simple MOSFET or NPN etc., transistors.
I had hard time struggling with Class A amps etc., but op-amp circuits were easier.

Since you are from Jalandhar, I really do not know wether you can source good quality MOSFET's etc., from Ludhiana or Jalandhar. Bangalore is a different beast altogether. You can get the best parts there, but in Ludhiana I guess you are confined to gur mandi.

The other problem is availability of analysis equipment. In college I had oscilloscopes to see wether it turned out right or wrong. If I assembled an amp today I wouldn't know where it went wrong.
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Old 20th March 2007, 15:48   #7
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Quote:
Originally Posted by tsk1979 View Post
Isnt it better to build a pre amp using OP AMps and an AMP to be put after the pre amp..
Sure there are a lot of chip amps that are out there. and yes these makes things a lot simpler. consider the LM3886 and it's cousins for example.

I used MOSFETs becuase in my time there were few chip amps available and discrete deviceds were easier to find. Remember TSK we studied in 2 different eras.
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Old 20th March 2007, 16:24   #8
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Yup, thats true different ERA's
I did my engineering 1997-2001, with 1989 made syllabus. So my experience was semi vintage too .
My amps amplified sine waves of varying frequencies, I guess if I made an amp myself it would involve noise issues, oscillation issues etc.,
How do you debug all this without a signal analyzer?
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Old 20th March 2007, 16:43   #9
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the chip amps like 4440 and 1280 as they are stereo amp....even when bridged will not give output greater than 50 watts rms....

to achive higher wattages firstly one will have to make the DC-DC power supply which is a challange itself as one would be requiring more than 24-0-24 volts to power an amp which would be making more than 400 rms...so it will be hard time ahead clip dont get dishearted we all are here to help you.....
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Old 20th March 2007, 19:58   #10
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Off Topic, nevertheless I saw some Burr Brown DAC's lying in an electronics shop at SP Road the other day... is it a necessity for building an amp?
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Old 20th March 2007, 20:47   #11
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Quote:
Originally Posted by s0uljah View Post
Off Topic, nevertheless I saw some Burr Brown DAC's lying in an electronics shop at SP Road the other day... is it a necessity for building an amp?
may be but in the pre-amp area mostly.....but who would be make that high end one....

also it is a DAC ( digital to analog converter) it will be used when any digital input is used like coaxial or optical is there....

Last edited by low_bass_makker : 20th March 2007 at 20:49.
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Old 20th March 2007, 21:04   #12
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Thanks for clearing that up LBM
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Old 20th March 2007, 22:57   #13
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Hi Clip,
Not to discourage you.
Building an Amp & building a car Amp is a totally different ballgame.

Would suggest you try building few small amps based on chips to gain knowledge and confidence and then move on to bigger project like a car amp.

As already indicated by LBM, most common chips can not hold more than 3Amps so theoretically you can not have more than 12v x 3A = 36W leave out few watts as losses, even with bridge mode they are not much efficient (read music to ears).

With regular 12V supply voltage
There are some popular Chips from ST & National (4440, 12xx) which you can try initially, but nothing from theses can pump bass in you car Sub. There are other options like Sanyo STK series, but require higher and symetrical power supply for operation.

A typical Car Amp consists of:
1. Power Supply
2. The main Power AMP
3. Preamp and active filter (usually)

For a DIYer the biggest challenge is to convert 12v DC to symmetrical power supply (+, 0, -) as per the AMP design. This Power supply should be able to deliver stable output voltage, regardless of the input voltage (usually the car electrical system will range in 9-15Vdc).
The DC-DC converter is usually a SMPS (Switch Mode Power Supply), few popular chips are TL494, SG3524, SG3525 etc. Generally SMPS used in car audio amplifier is the push-pull system with switching frequency between 20-70Khz. Also it needs to have some sort of protection to protect the AMP and your expensive Sub from overload, heat, and other abnormal conditions.

There are quite a few popular designs floating around for the main amp you can search on the web.

You can select a matching preamp and active filter design based on your Main Amp.

Not sure about Jalandhar, but you can get few good amp kits from Rajindra Electronics in Sec-35, Chandigarh. For spares and other components you can try Anand / Anil electronics in Sector 18, Sonia electronics in sector 42, above Gobind sweets.

Keep us posted...


Quote:
Originally Posted by navin
It used Hitachi 2SK135 and 2SJ50 MOSFETS (I hope I have these numbers right becuase my memory is not very good today).


I am big fan of Hitachi Mosfets, the popular design around this matching pair was Crescendo and Mini Crescendo, could not locate these for long time, last i checked on Lamington Road it was Rs750/- a pair, too steep.
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Old 20th March 2007, 23:58   #14
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Originally Posted by Sutra View Post
switching frequency between 20-70Khz.
that can be reduces if one plan for a D-class as tehe freq response would not be greater than 300 hz.....
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Old 21st March 2007, 04:07   #15
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hi guys,

thanks for your suggestion. i could have never imagined getting help from pros like you.

im a little confused now. will let you know in a day or two what my plan is. if a sub amp is not possible, ill build an amp for home duty.

regarding the part supplies, i just went 2 the electronics market in the evening. you wont believe the size of the market. it like 200 - 300 shops for electronic and electrical parts and im not exaggerating. the guy i know has all the parts including the lm3886(dont rememer the exact no.) and they can buils any kind of dc -dc ac-dc transformers. they can even make toroids. and i can get a pcb made here accoring to my requirement in a day. im really happy with the guys here. they are really helpful. and they have good quality parts. i can even order the parts and thet will get it in 3-4 days max.

also i can test the amp at the regional engg collage here in my city. they must be having the appropriate equipment. let see if i know someone there.

what im thinking now is to diy a home amp but i need good quality drivers which arent available here. if anyone can help me with the prices for good quality drivers?

now im really confident with you guys pouring in your suggestions and the technical knowladge.

thanks guys and the gurus

ot - just read car india and saw the pics of the octy install done by gunman jb and mr patel. im really happy for them. congrats dudes. you make us bhpians proud. keep up the good work.

edit - their names are mentioned too.

Last edited by clipto333 : 21st March 2007 at 04:12.
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