Ultra Low Cost Amp Design

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Richard C: Right On!

I just made an experiment (see below) to see how the MOSFET's should be temp. compensated. You need around 2.5 V on the VBE multiplier, and some 5.5 V of temp. stable Zener voltage on top of that. I used a varialbe Zener diode to find these values, why not use steady resistors in the VBE multiplier, and a variable Zener diode in the real amp?

The Variable Zener Diode is: TL431A from TI. (cheap).

You don't need the 'Emitter' resistors! Just short them together as i did.
 

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Sure PerAnders, we discussed the use of Switched Mode PSU's on page 5.

It is not so expensive. This one is factory wound for the UL listing, but since it only contains about 25 windings in all, any DIY'er can easily make it at home. The ferrite cost the formidable sum of 1$, and 2m of electrical wire cost .. nothing. (almost). So a 1kW transformer for around 1$ .. not bad i think. Of course you need a bit of support circuit, but it can also be put together cheaply.
 
Lars Clausen said:
It is not so expensive. This one is factory wound for the UL listing, but since it only contains about 25 windings in all, any DIY'er can easily make it at home.
.... if he/she has accurate instructions... very important if the switching speed is high.

The problem with SMPS is the rather high cost for the support parts. A 1 kW PS is not very cheap but light...:)
 
Peranders: Here are the schematics of a design i made a couple of years back. It actually played (and well too) for several months as a bird-nest circuit, before we took it out of the demo room, so no one would get hurt. . :)

A better image can be seen here: http://www.lcaudio.dk/smps1dia.jpg

Of course it can be tweaked with a xtal oscillator, and maybe a real Gatedriver IC, but in think the performance of this low cost circuit is quite good. And the price is low on all parts.

WARNING! Build at your own risk, HIGH VOLTAGES !!!
 

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You have to read a 500 page book to get all the details on the CE approval.

Strictly you actually need the PFC, but very few manufacturors follow this rule, so i think you can get approval even without PFC. Not quite sure though.

And next CE approval is not enough, you also need UL approval and 3 other approvals, to cover the entire world market. Each cost a load of money to obtain, why we never released a Switched Mode PSU. And should you change anything, you have to start back at square one. We are talking at least 100.000$ in approval costs for one design.
 
If the harmonics are to high you will not get it through a CE certification no matter what. I think if it is a class a amp pulling 300W. Without PFC and inputfilter you will never be able to meet there criteria.

On the other hand if it is a class AB design pulling like 10 - 60W i actually think it will walk right through the test. even if the SMPS is a 500W peak design.

So with a class H design, i would believe the design is ok. But only if the tests are as loose as they some times is.

Like only driving a the amp into 8Ohm at a low power level which is identical to an average listning level.

But on the other hand.. It is not cheap, if the test fails. It like throwing 20000DKR out the window! :D
 
The thread is opened again and I’d like to salute this step of moderators. The name of the new born Texas thread is however very maliciously named. Its name certainly doesn’t have anything with its content. But since these are my first posts that finished in Texas (I am posting here about year and a half), I am honored and I’ll not make a question about this. I just don’t like Peter’s last sentence (threat) about the “bashers” in the last sin binning notification. Seems like this is definitely advertising free space in which can be dangerous to counteract to the advertising.

Richard C, Re: your statement in the WCTC thread: I’ll not post anything more in this thread, so you are safe about this. Among the other reasons I’ll not post because the suggested solution doesn’t have much with the way to make a cheap amplifier. Tip for the ultra low cost amp: deal with the supply, it is ridiculous to try to make something better than LM3875 for $6 (or less). Btw, you’ll not use it anyway in the amp, but to lower the total cost of the system significantly, avoid spending EUR200+ for the clock.

Good luck making cheap amplifiers,
Pedja
 
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