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FW: RE: 2 questions (Leif Åsbrink Oct 14 2002)

-----Original Message-----
From: owner-linrad@xxxxxxxxxxxxxxxxxxxxx
[mailto:owner-linrad@xxxxxxxxxxxxxxxxxxxxx]On Behalf Of Leif Åsbrink
Sent: Monday, October 14, 2002 4:48 PM
To: linrad@xxxxxxxxxxxxxxxxxxxxx
Subject: RE: [linrad] 2 questions

Hi All,
> Re the power supply, I would be tempted to use a very high quality linear
> PSU. I still don't trust those switch mode supplies. Maybe it's because in
> my profession (pro audio) I have yet to hear a high power audio amp with a
> SMPSU that sounds anywhere near as good as a top amplifier with a
> conventional PSU. So I have this in built bias against them.

Your experience is not relevant here. In audio, a switch mode supply will
loose its low output impedance when overloaded. That means that short peaks
of overload will cause serious voltage swings that will distort heavily.

Nothing can compete with really big capacitors which is a natural part of
linear supplies. I do not know, but my feeling is that large capacitors
that store a lot of energy is the reason for audio performance.

The switchmode supply is elegant in that the capacitor is made much smaller.
The voltage across the capacitor is allowed to have a large ripple and
the switchmode regulator can take care of the large voltage variation.
A linear supply does not want to dissipate all the heat so the primary
voltage stays within a much narrower range.

It is of course another thing that ill designed audio equipment may 
pick up interference from the switcher - or the switcher may produce a 
lot of RFI on the low HF bands.

For WSE converters any "normal" power supply is fine.


Leif  /  SM5BSZ