Class A amplifier design help...car audio

Discussion in 'General Electronics Chat' started by chunkmartinez, Oct 20, 2013.

  1. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    Hello all....I am wanting to learn as much as possible about SMPS circuit design and anything new about audio amplifier design that I can.

    I want to design and build a Pure Class A amplifier for car audio using an smps power supply. Why class A if AB is more efficient and sounds just as good? The novely of it, for fun etc...

    Since class A amplification will create so much heat My goals will be 100w RMS x 2 channels(stereo) at 4 ohms.

    Where to start?

    Should I use an opamp for the pre-amp or design a discreet pre-amplifier? I heard Discreet component class A circuits can be hard to design what do you all think?

    On the SMPS side, I figure I will use the same topology that most car audio amps use, a push-pull, or can I use other topologies? This is where I will learn and see what I can do. What switching frequency would be good to use(how high can I go), any ideas on toroidal cores for the filtering and the transformer, wire guage, types of mosfets to use for the smps, and for the audio side and how many I would need for my target?
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    So, you basically want to design an audio amp so inefficient it will need cooling from a garden hose but build a switching converter to feed it to conserve power?

    Interesting......


    IMHO, it is impossible to hear any difference between a Class A amp and a WELL DESIGNED class AB, but that's just my opinion.
     
  3. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Push pull is the way to go. SW frequency is as high as possible with acceptable losses in the switching magnetics and FET devices.

    BTW: switchers are like small radio stations. Preventing the EMI from seriously contaminating the sound quality is quite a challenge.
     
  4. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    I meant using SMPS for the power supply like all amps use. I will Not be converting the output to class D or anything. Like I said the reason I want to go with a class A is for the novelty and the learning experience.
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Now that you gave the OP a solution to the cooling problem, I want to see this thing get built!
     
  6. bertus

    Administrator

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    Last edited: Oct 21, 2013
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  7. killivolt

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    Jan 10, 2010
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  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Count me in.

    I like to see how OP can keep a class A @ 200W RMS playing at for than a few hours. I believe OP will need a KW PSU
     
  9. #12

    Expert

    Nov 30, 2010
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    Here are 2 ways to do it.
     
  10. BobTPH

    Active Member

    Jun 5, 2013
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    I think it would be cool if your amp could also be used as a toaster.

    Bob
     
  11. #12

    Expert

    Nov 30, 2010
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    Too much difficulty keeping nichrome the same resistance as it heats up. This will probably have to settle for being a space heater.
     
  12. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    space heater.....
     
  13. BobTPH

    Active Member

    Jun 5, 2013
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    But that is too easy. Maybe build it onto a set of headphones so that it can also be a hair dryer?

    Bob
     
  14. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    After thinking about it you guys are right. What do you think about a full-range class D amplifier? I'm thinking 150W x 2. Any suggestions about components? Can I use a hip4080 for the H-bridge driver?
     
  15. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Don't be a quitter. Class A can be fun. Old GM (and possibly other) cars used them on their little AM radios (as TO-3 PNP Germanium). Instead of quitting, lower your expectations. Try something in the 5 to 10 watt range. It wont be nearly as fun since a flowing garden hose will not be required for cooling.
     
  16. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    I have seen some lower power circuits online so I thought about trying them...I will post back when I find one I like.
     
  17. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    That's what I told my wife on our second date..... been married 32 years now.;)
     
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  18. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Ha! Thanks!
     
  19. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    Actually I am leaning towards switching circuits now adays. I am going to try and make a buck converter today to drop my LARGE transformer's 40v supply to 12v. The transformer looks to be able to supply 2kw. I want to use the transformer for repairs etc...

    So....While I am at it, I will need to start delving into switching. I want to either go with a simple 555 timer, comparators, or my tl594 IC I have. So I want to go with a full-range class D.

    Does anyone have an idea on components for a buck converter from 40 to 12V. Since I have a large current ceiling, should I use large wire for current handling? I have 10guage magnet wire...and big shotky diodes.
     
  20. #12

    Expert

    Nov 30, 2010
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    Not for 2KW

    I wouldn't even bother to ask the TI simple switcher calculator for a 150 amp supply.
     
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