[j4cbo]

The general wisdom in the headphone amp world is that switching power supplies are bad. They produce all sorts of nasty ripple which can easily affect the audio band, much more so than a typical linear regulator.

So I'm wondering, why not combine the two? A linear regulator like the LM317 is capable of 80 dB of ripple rejection, and wouldn't dissipate much power if it were fed by a switching supply just high enough to be away from the dropout region. This would be particularly useful for pocket amps, since AAs and AAAs are rather cheaper and more common than 9v batteries, rechargeable or not.

Anyone tried this sort of thing?

 

[dsavitsk]

Quote:

Originally Posted by j4cbo /img/forum/go_quote.gif So I'm wondering, why not combine the two?

Linear regulators do very little to reduce high frequency ripple. But, if you use a choke/ferrite/inductor to filter this out, then it works okay. This is how the HPDAC's power supply works.

-d

 

[j4cbo]

Hm, interesting.

The output of the switcher has a capacitor to ground, then the ferrite in series, then to the opamp chip. Should there be a large aluminum/tantalum across the opamp in parallel with its decoupling cap, or is that unnecessary?

 

[mono]

You are misinterpreting what dsavitsk wrote, it is not a matter of "look at what's part of the supply then subtract those parts", it's a matter of adding an entire additional stage of filtration.