Class A amplifier design help...car audio

Thread Starter

chunkmartinez

Joined Jan 6, 2007
180
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?
 

bountyhunter

Joined Sep 7, 2009
2,512
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.
 

bountyhunter

Joined Sep 7, 2009
2,512
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?
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.
 

Thread Starter

chunkmartinez

Joined Jan 6, 2007
180
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.
 

bertus

Joined Apr 5, 2008
22,270
Last edited:

killivolt

Joined Jan 10, 2010
835

Thread Starter

chunkmartinez

Joined Jan 6, 2007
180
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?
 

GopherT

Joined Nov 23, 2012
8,009
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?
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.
 

Thread Starter

chunkmartinez

Joined Jan 6, 2007
180
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.
 
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