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Posted to uk.d-i-y,uk.rec.audio
Phil Allison[_2_] Phil Allison[_2_] is offline
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Default amp new PSU capacitors


"The Natural Philosopher"

Unless its split rail with two 80V caps, or an H bridge..in which case
yes, its abut 400W.


** That is a bit optimistic.

1. If the filter electros are each rated at 80VDC working and one sensibly
allows for higher than nominal AC supply - then the *unloaded* DC rails are
likely to be +/- 74 volts.

2. If the AC tranny is of conventional design ( toroidal or E-core) then the
regulation factor is such that the average DC rail will drop under load by
about 12%.

3. If the capacitance is a typical value like 6800uF for one channel - then
the p-p ripple voltage under steady load is about 4 volts - more if the
audio test frequency is under 100 Hz.

4. An output stage is never able to swing to the full extent of the
available DC rail voltage - particularly so if the output devices are
lateral mosfets. Assuming a typical complementary Darlington output stage
with emitters supplying the load - the output can swing within about 5 volts
of the available supply with an 8 ohm load.

Adding this up we have:

74 - 9 - 2 - 5 = 58 volts peak.

So the "rms" power on sine wave into 8 ohms will be 210 watts.




...... Phil