Re: [AH] Looking for an OB-8, OB-SX, or OB-XA power transformer

From Oakley Sound via analogue
Sent Wed, Sep 26th 2018, 09:03

 > Use a switching power supply with higher voltage output and then add 
a linear regulator.

I have used this too on a few occasions. The most recent was a CLS-22 
with a very noisy transformer. I replaced it with two 18V switching 
units. The result was very satisfying - although I did have to add a 
proper earth as the switch mode blocks needed this to dump all their 
nasty switching spikes to.

Thankfully, quite a few 18V units do exist so we can create 15V via a 
linear regulator. I sometimes add a RC filter between the two which can 
normally fit in place of the much larger smoothing capacitor. LC may 
well be better but RC is easier.

The one thing that slightly bothers me with using multiple switchers in 
one application is the possibility of heterodyning with the switching 
clocks. I wish they had some sort of sync input/output to lock them 
together. In bigger gear I much prefer to go with a single multiple 
output switch mode PSU.

One problem I have found is that some items with CPUs or DSP don't power 
up correctly as the outputs of the SMPS come up too slowly. I had to 
hack the reset lines on a Mono Evolver I added an internal SMPS to, 
otherwise it wouldn't power up properly.

Finally, I have never yet seen a switcher that is as quiet as a linear 
PSU. At least in terms of p-p voltage spikes on the output lines.

Tony

www.oakleysound.com