PSU Rectifier Before The Transformer. Cart before the horse?

[beatpoet]

I opened up a PSU today and saw:

AC Mains rectified, regulated, then fed into an oscillator with a very tiny iso transformer. Why haven't I seen this in the pro audio designs floating around here? It seems like it would be a cost and size cutting device.

AC Mains -----> Rectifier --------> Single transistor regulator ------> Single transistor oscillator --------> Miniature Iso transformer --------> Rectifier/filter

 

[enthalpystudios]

isn't that just a switching power supply? cuts down on transformer cost at the expense of hi freq switching noise on the voltage rails. potentially can dump switching noise into your audio, but there are def. major gear manufacturers that use them.

not worth it if you aren't a company with overhead and cost cutting needs.

 

[JohnRoberts]

[quote author="beatpoet"]I opened up a PSU today and saw:

AC Mains rectified, regulated, then fed into an oscillator with a very tiny iso transformer. Why haven't I seen this in the pro audio designs floating around here? It seems like it would be a cost and size cutting device.

AC Mains -----> Rectifier --------> Single transistor regulator ------> Single transistor oscillator --------> Miniature Iso transformer --------> Rectifier/filter[/quote]

The approach, or variants on that are used in several high power audio amplifiers to save cost/size/weight pulling tens of pounds out of an amplifier.

An additional refinement PFC (power factor correction) spreads the current draw over the entire waveform which reduces peak IxR losses in mains distribution.

JR

 

[walter]

Behringer uses that kind of supply in alot of their gear, but I think they are moving away from that.(the FCC is so picky). The line voltage, anything from 100v to 240vA/C is rectified. A high frequency is generated from the rectified voltage. That high frequency needs less iron so smaller transformer/less weight/less shipping cost. A couple years ago I worked on a car radio. It had + ground, and used a vibrator tube. The six volts from the cars generator went to the vibrator to create an A/C signal, that was bumped up through a transformer and rectified to supply the tubes. Very similar concept.

 

[beatpoet]

I didn't know audio people still liked vibrators.... :guinness: