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Old 1st July 2013, 09:00 AM   #1
Leify is offline Leify  Sweden
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Default F5T with 56V rails?

Hi all,
I just purchased the PCB's to the F5T from the forum store an aiming to build monblocks. I have a big transformer (2.2 KVA) with 2x40V secondary that will aprox give 56V rails. Im thinking of to setting the bias to about 25-30W class A for each monoblock. What power should I expect in class AB then?

Im looking forward to your answers.

Br
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Old 1st July 2013, 09:28 AM   #2
AndrewT is offline AndrewT  Scotland
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Use the maximum Vpk available from your rails after subtracting a bit for losses through the amplifier.
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Old 1st July 2013, 09:43 AM   #3
Leify is offline Leify  Sweden
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Im not sure I understand. Please explain.
Appreciate your effort.
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Old 1st July 2013, 10:01 AM   #4
AndrewT is offline AndrewT  Scotland
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Standard F5.
Supply rails ~+-25V
Maximum output ~20Vpk
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Old 1st July 2013, 10:58 AM   #5
Leify is offline Leify  Sweden
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sorry still don't get it. What power could I expect.
br
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Old 1st July 2013, 11:15 AM   #6
flg is offline flg  United States
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You could possibly get 52V rails?

rms power = (Irms*Irms)*R
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Old 1st July 2013, 11:23 AM   #7
AndrewT is offline AndrewT  Scotland
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Is it the calculation for predicted power that you need?
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Old 1st July 2013, 11:37 AM   #8
Leify is offline Leify  Sweden
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yes pls
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Old 2nd July 2013, 09:12 AM   #9
AndrewT is offline AndrewT  Scotland
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Power (in watts) = I dc * Vdc = Idc^2 * Rload = Vdc^2 / Rload.
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Old 2nd July 2013, 09:57 AM   #10
Mooly is offline Mooly  United Kingdom
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Assuming the amp (which I'm not familiar with) can leave class A and continue to deliver increased output up to the point at which it clips (as it reaches the limit of the rails) then,

1. Your 40-0-40 tranny gives -/+56 volts.
2. In practice your amp might swing (say) -/+ 48 to 50 volts into 8 ohm resistive.
3. That becomes -/+48 volts peak to peak.
4. Vrms is Vpeak (48 volts) / √2 which is 34 volts rms
5. The "power" into 8 ohms is Vrms*Vrms/8 which is 144 watts rms
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