Switched Mode vs Linear Power Supply

Not so fast

I would argue that switched mode has several advantages over linear supplies, particularly for power amps.

Your original question is for a preamp. I am 100% sure you will get better sound with a linear supply. However it is useful to consider what happens when you go to a power amp.

Try to design an 80V 80A continous linear supply for example.

I predict that within 2 years, 80% of all audio power amplifiers will use some form of switched mode power supply.

I further predict that 10% of these will do the job right and use high quality construction and thus obtain better sound quality than would normally be possible, particularly at low frequency.

I also predict that 50% of power amplifiers will be digital (switched mode for amplification) within 2 years, and that 20% of these will sound good.

The reason why SMPS is not accepted today is probably a competency issue with audio designers + extreme cost cutting. Quality has a price so it is somewhat strange to see that SMPS is not used more even today as correcly executed designs have low cost, particularly when produced in volume.

SMPS and preamps

One of the nicer switchers I built used a linear post-regulator (LM317). This significantly reduced (but didn't eliminate) the switching transients. When in doubt use a linear supply. When in further doubt, use a linear power supply with discrete, low noise components.

I do want to try out the low noise push-pull transformer drivers from Linear.


2002-02-06 9:16 pm
Lots depends on the voltage differential you have to bridge and the frequency involved. Good HV components are not cheap, and good smps designers are not abundant. This is an art, as much as designing amps.

On the other end, for getting a +/-15V out of a battery, they are great, but then the power is not great, and the frequency can be high enough.