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Old 13th March 2012, 10:13 PM   #121
biju55 is offline biju55  India
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For bba-3 front end need to connect two ba-2 out put stage .if i use 5 pair of mosfets for each out put stage , how many watts rms can expect from this amp ( +/-24volt rail )
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Old 14th March 2012, 01:48 AM   #122
JimM is offline JimM  United States
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In simulation with 24 volts +/- the front end will swing around 36 +/- peak to peak
which will give you around 25.45 volts rms. So around 80 watts at 8 ohms and around 150 watts at 4 ohms. this does not take into account the drop in the out put stage so around 75watts into 8 ohm and 145 watts into 4 ohm. 5 pair of output should be able to give you the 145 watts into 4 ohm. Once again class AB not sure about pure class A.
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Old 14th March 2012, 03:32 AM   #123
rsdio is offline rsdio  United States
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Quote:
Originally Posted by JimM View Post
In simulation with +/- 32 volt supplies I get a peak to peak swing of around +/- 45 volts from the front end so Vrms = 31.82volts and p= vrmsxvrms / RL or around 126.5 watts for 8 ohm and around 253 watts for 4 ohm.
I've never seen anyone report peak to peak swing with +/- voltages. Did you mean peak to peak of +45 V? Isn't peak to peak an absolute value, basically? Also, Vrms should be 15.91 V for a 45 V peak to peak signal. Besides, I don't see how you can possibly get more than 22.63 Vrms from a +/-32 V supply. The only way you could get 31.82 Vrms is with a square wave or something close; certainly more harmonics than a pure sine.

If there is something that I am missing, then my apologies: please explain.
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Old 14th March 2012, 12:49 PM   #124
AndrewT is offline AndrewT  Scotland
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Jim has never learned how to manipulate voltage units.

Jim's explanation of voltage is completely wrong and as a result his predictions of power are worthless.

+-32Vdc supply rails cannot allow a BA3 to output +-45Vpk at the speaker.
It could allow an output of 45Vpp.That is very different.

Let's assume the prediction is 45Vpp then the sinewave equivalent is 45Vpp / 2 / sqrt(2) = ~15.9Vac.
the predicted sinewave power is 15.9Vac^2 / Rload = ~32W into 8r0.

However I suspect that the 15.9Vac prediction based on 45Vpp is too low.
I would expect (32+32) / 3 as the likely Vac into a high resistance load. Into an 8r0 load expect ~ a couple of volts less and into 4r0 another couple of volts below the 8r0 value.
Prediction into 1k0 ~ 20Vac
Prediction into 8r0 ~ 18Vac+-1
Prediction into 4r0 ~ 16Vac+-2

And all I need is a pencil and paper.

One MUST be able to check the outputs of any software based prediction for accuracy before one can rely on the results.

That "MUST" demands that the user must also be able to determine manually from a reasonable model very similar results. That requires a deep understanding of what the software is doing for the user.
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Last edited by AndrewT; 14th March 2012 at 12:56 PM.
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Old 14th March 2012, 04:51 PM   #125
JimM is offline JimM  United States
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As I said in simulation the front end shows with a +/- 24 volt supply in balanced mode will swing around 45 volts peak to peak. I also said this does not take into account the drop in the output stage.
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Old 14th March 2012, 05:18 PM   #126
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Old 14th March 2012, 05:35 PM   #127
flg is offline flg  United States
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I don't really care if some people haven't learned some things but, any one who says "Jim's explanation of voltage is completely wrong and as a result his predictions of power are worthless." should be forced to 6 months, minimum, Moderator duty. To learn how to cumunicate How to comunicate in an appropriate way to others who may not be so experienced...
I know, it goes on and on... In 6 months there will be all these newBs who havent read anything but car stereo crap and know almost everything the rest of the world does???
I'm sure there could have been someone who would be making you feel like Jim right now, maybe your mother?, but... The content was probably correct. But I don't F$%^& give a %^&* when I read that BS!
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Old 14th March 2012, 05:43 PM   #128
6L6 is online now 6L6  United States
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I don't really care if some people haven't learned some things but, any one who says "Jim's explanation of voltage is completely wrong and as a result his predictions of power are worthless." should be forced to 6 months, minimum, Moderator duty. To learn how to communicate
I agree 100%
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Old 14th March 2012, 05:45 PM   #129
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no no and no

members are obliged to know ........

members aren't obliged to communicate in good spirit .

this is professional site , with paid membership , so wtf amateurs and not worthy are doing here !!?? !!!
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Old 14th March 2012, 05:51 PM   #130
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Quote:
Originally Posted by JimM View Post
In simulation with 24 volts +/- the front end will swing around 36 +/- peak to peak
Quote:
Originally Posted by JimM View Post
As I said in simulation the front end shows with a +/- 24 volt supply in balanced mode will swing around 45 volts peak to peak.
Right, said Fred.
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