swinging question ....

[sakis]

many know that my theory is poor ...at least i am working on it and also try to remain open to advice ...

so here is a swinging question

in a classic AB topology i have one amplifier that is supplied with 60+60 volts about and the output of my amplifier at no load conditions is about 40 volts

now probably at resistive load conditions and full drive my rails are going to dive at least 10 volts that is about 50 or even less while the output will also drop but not really much ...lets say from 40 to 38 volts ....


so all transistors ( 6 per amplifier board) will face a VCE from 10 to 20 volts


then more questions like :

***is it better that output swings closer to rail Voltage ???
*** does the above setup 6 outs with VCE from 10-20 volts sounds reasonable enough ??? and safe enough ???

now be nice to me people ...also keep your answers in plain ....greek !!!

kind regards sakis

[AndrewT]

Hi,
+-60Vdc
40Vac from output into open circuit.
Vce of outputs at peak output voltage ~60 - 1.414*40 = ~3.44V.
The Vre should also be subtracted leaving Vce~3.42V

Let's assume 50Vdc at the bottom of the ripple when fully loaded.
Let's assume 1Vre at peak current.
Vce could be as low as that earlier value i.e. 3.4V
Max Vout fully loaded will be 50 - [1+3.4] ~45Vpk ~ 32Vac
That would be the maximum on medium term continuous power.
The transient voltage and current will be much higher due to the very small sag in PSU voltage on short term transients. It is possible on low duty cycle sinewave testing that you could get 50Vpk to 55Vpk at the output.

These are the maxima to be expected.
You should not ask for music signals that exceed these short term and medium term peak voltages.
If you ask for more the amp clips. It should not destroy itself.

[sakis]

so ...eventhough this is not plain greek in a few words do you think its enough or not ???

[AndrewT]

I think you are asking the wrong question.

All amplifiers should be designed to survive mild clipping and good amplifiers will survive gross clipping and ensure the load is undamaged as well.