Re: amplifier redux


"geezer" <liveoak.nine@xxxxxxxxx> wrote in message
news:9e347a7b-6302-4c39-a4a8-910d17162067@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On May 27, 10:49 am, klu...@xxxxxxxxx (Scott Dorsey) wrote:
I am thinking it is due to the lack of ability to supply large currents
at short peaks, which is a pleasant side effect of having a big 120 Hz
filter on the output nof your power supply.

I thought the switching supplies COULD supply all the current needed.
If not, why not just use big capacitors? You'd still be saving the
expense & weight of the transformer...

----------------------------------------------------------------------------------------------
One could add a big capacitor bank to a switcher, and, as Scott mentions,
carefully vet the output for hash and filter as necessary, and get a good
result.

In the case of linear supplies with transformers operating at line
frequency, the limiting factors are:

1. The amount of iron in the core, which largely determines the amount of
current a transformer can supply.

2. The waveform coming out of the rectifiers, which goes to zero 120 times a
second. The gaps are the responsibility of the capacitors. So, one needs a
lot more capacitance than in the case of a switching supply, where the
waveform has a much higher frequency.

If you're asking, why not eliminate any kind of transformer, and connect the
rectifier bridge directly to the AC line, Bob Carver did this in one
amplifier. It is considered unsafe by modern standards. A transformer is a
safety device. A person who simultaneously contacts any part of the
amplifier circuit, and earth ground, is protected from serious shock by the
transformer.

Bob Morein
(310) 237-6511


.

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