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DjLeco 27th August 2010 10:45 AM

Class AB amp made by me.
Is a perfectly simetrical amplifier, this will be my prototype.

Power supply will be +/- 95 Vdc, I have tested at +/- 112 Vcc (idle), dropping till +/- 92Vdc (at full power on dummy load).

I estimate around 500Watts on 8 ohms and 800Watts at 4 ohms.

Protection will activate, under 2,66 ohms load, killing the differential INPUT stage.

Some testing movies on dummy load on sinewave:

YouTube - 1 Prezentare+Reglaj Bias.MOV

YouTube - 2 Bias Reglat.MOV

YouTube - 3 30Hz-200Hz On 8 Ohm.MOV

YouTube - 4 200Hz-60Khz On 8 Ohm.MOV

YouTube - 5 Explicatii Dupa Test.MOV

YouTube - 6 100Hz-15hz + Scurt.MOV

YouTube - 7 30Hz-20Khz On 4 Ohm.MOV

YouTube - 8 Idei Finale.MOV

Testing on musc signal:

Part 1 music test

YouTube - Part 1 Music Test.MOV

Part 2 music test

YouTube - Part 2 Music Test.MOV

Part 3 music test

YouTube - Part 3 Music Test.MOV

Maximum output power on 8 and 4 ohms

YouTube - Maximum Output Power On 8 And 4 Ohms Speakers..MOV

1 W 8 ohm linearity

YouTube - 1W- 8 Ohms Linearity.MOV

Some amusement tests:

YouTube - Film 1.MOV

YouTube - Film 2.MOV

YouTube - Film 3.MOV


YouTube - Film 4 Dif.MOV

YouTube - Film 5.MOV

YouTube - Film 6.MOV

YouTube - Film 7.MOV

And some dreptunghiular and triunghiular signals testing:

YouTube - Dreptunghhiular 1.MOV

YouTube - Dreptunghhiular 2

YouTube - Dreptunghhiular 3.MOV

Please have patience and watch all movies from start till the end.

Free for comments, opinions, etc.

Please don't ask fost schematics, that's my prototype.

Thanks for understanding.

AndrewT 27th August 2010 10:55 AM

500W into 8r0 from loaded supply rails of +-92Vdc is a good result. You are losing just 2.56V from supply to output (89.44Vpk).

The 800W into 4r0 result is pretty poor by comparison. It is 1dBV down on the 8r0 result and shows a voltage loss that increases from a good 2.56V to a very poor 12Vlost.

Your protection is badly designed if it damages the front end when triggered.

Check what the VAS stage currents are when the protection is active (triggered). The VAS must be self protecting if the output can be clipped and/or protected.
Are catch diodes fitted across the caps and output rail to limit the back emf from the moving driver VC and capacitors/inductors?

DjLeco 27th August 2010 11:04 AM

AndrewT, please have patience to watch ALL movies entirely ,and we'll speak after.

Using 4 ohm instead 8 ohm for dummy load, the power supply is sagged and dropes more significantly!

I never saw an amplifier AB class wich his power in 4 ohms will be doubled comparing to 8 ohms power.

Also, outputs power that I said (500 and 800 watts) are relative.

You will see that after watching all movies entirely.

The protection works flawless, the amplifier will have separate section for limmiter and mutting.

AndrewT 27th August 2010 11:42 AM


Originally Posted by DjLeco (
I never saw an amplifier AB class which his power in 4 ohms will be doubled comparing to 8 ohms power.

neither have I.

Cordell suggests a good amp will give 180% into a half resistance load.
I set a slightly lesser standard than his.

I have built many amps that are -0.4dBV to -0.6dBV down into halved load resistance.
I would reject an implementation that was -1dBV down into 4r0 ref. 8r0.

I will repeat, somewhat re-phrased, what I said earlier: your reported 8r0 power performance is good. Your reported 4ohm power performance is far from good.

I do not need to watch movies to read this.

east electronics 27th August 2010 11:43 AM

well ...that looks very promessing ... i will not go to calculations or thepry but for starts the pcb is very badly designed ...way too many parallel lines and proximity between traces will cause some trouble ...

respecting your statement about the circuit but still it would be interesting to see

kind regards sakis

tryonziess 27th August 2010 11:44 AM

Could you post a schematic of this amplifier please. Looks like a very professional pcb you have made. Nice work.


DjLeco 27th August 2010 11:44 AM

Symetrical input stage (mirrored) receive 1mA current, from precision constant current generator, thermally compensated.

Watching Makie M1400 schematics, mine amplifier is more more simplistic, and does't look the same.

Sorry, schematics will not be posted because is mine prototype.

PCB is JUST for testing purpose, professional PCB will arive in 2-3 weeks.

So on this simple PCB works like that, in a pro PCB will work minimally the same!

I'm satisfied with the results of it.

SY 27th August 2010 11:47 AM

:cop: Non-English post removed. Please see the forum rules. One's English doesn't have to be great, but English IS the official language of this forum due to wide international participation.

donpetru 27th August 2010 12:00 PM

SY, I understand the forum rules but you must to make an exception!

@Dj Leco, congratulations for the achievement. An yes, your amplifier is more simplistic that M1400. Eventually, you use a protection diagram transistors like that (see post no.10, fig.4):
circuit de protectie la scurtcircuit pe iesire la amplificatoarlee audio - Comunitatea Tehnium Azi

Nice day.

DjLeco 27th August 2010 12:14 PM

Mine protection Kill entire input stage, not pilot transistors!

That means at accidental shortcircuit on outout(as you can see in some movies posted), will shot down differential input stage.

Also second protection will activate with some delay,(mutting) the general input level, untill overload dissapear.

Also will be thermally protection with bimetal or LM350 circuit.

But all these in other module separately.

Thanks to all for encouraging, my project.;)

Excuse some mismatch spelling, too!:rolleyes:

donpetru, I must be logged on that forum, please pick up that schematic, upload it on tinypic and follow it's link, here, thank you!

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