amp new PSU capacitors
Phil Allison wrote:
"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.
No. 58 volts peak TO peak.
So the "rms" power on sine wave into 8 ohms will be 210 watts.
No, slightly over 50W.
..... Phil
|