What's the skinney on using switching power supplies for Hi-Fi?

[tweakk]

I'm fooling with a TA2024 SI amp and heard that it sounds it's best with a 3A or more SMPS over a SLA or linear supply.

Is there a way to clean-up the output of a switching supply? Is it really necessary or are some people just picky. can a SMPS work well as a pre-amp supply?

TIA!

SORRY! I WANTED TO POST IN POWER-SUPPLY FORUM.......

[Bigun]

I've never tried an SMPS, although I have a couple in the basement. I believe there are some nay sayers out there who would avoid them but like most audio technology the early versions were bad and gave things a bad reputation that the modern stuff doesn't deserve.

I don't see why a well spec'd SMPS wouldn't be a good choice for pre-amp where current draw isn't too high.

My suggestion is make sure the current output of the SMPS is well above what the amp needs and then to keep things clean try and physically separate the SMPS from the amplifier or at least ensure some electrostatic screening - it's the high frequency noise from the psu you want to keep out of your amp (same story with linear psu using rectifiers by the way). To keep the dc output clean you could add a good choke - capacitor filter.

Edit: p.s. the moderators can move this thread to the psu section.

[tweakk]

Thanks for the reply.

I might try a regulated medical unit by SL Power.

[indianajo]

There was a guy from audiopower.it who ran a thread in power supplies touting his switchmode designs in 400w and 600 w split supplies for power amps. He claimed 87 db s/n with the unit in a box. search the power supply forum for dps400. (if you search the internet for that it comes up with cheap PC computer supplies.) His prices were in Euros, which is down right now vs the dollar.

[tweakk]

Cool

That's exactly what I'm looking for.

[abraxalito]

Originally Posted by tweakk

Is there a way to clean-up the output of a switching supply?

It depends on the particular power supply. If you look at the Linear Technology website under the application notes you'll find design examples of astonishingly low noise switching supplies. They do have to be designed for low noise though, just filtering the output of a bog-standard brick won't give the lowest noise.

Is it really necessary or are some people just picky. can a SMPS work well as a pre-amp supply?

SMPS work fine for power amps and often better because they're regulated. But for a phono preamp, I'd not use an off the shelf brick myself without some serious filtering. So much so as to make a linear supply a more cost-effective solution. There has been a fair amount of prejudice against switchers in the audiophile world, but its been decreasing for some time.

[Enzo]

It is like anything else, a well designed product will perform well. a poorly designed product will perform poorly. Asking if an SMPS can be cleaned up is like asking if a linear can be cleaned up. Certainly we know linear supplies can be quiet as a mouse, but the POTENTIAL was always there for hum and ripple, and transformer coupling into other things. What SMPS work on within themselves is a real ugly waveform, but that doesn;t have to escape to the outside.

REcording studios are chock full of signal processing gear that uses SMPS. They don;t seem to have any trouble with it. I can think of such products that used SMPS at least 25 years ago.

[Nelson Pass]

Two items,

1 Use a supply whose output rating is at least the peak
current that you will draw.

2 I recommend LC filtering after the supply's output and some
physical distance and/or shielding between the supply and the
circuitry.

[Wavebourn]

Originally Posted by Enzo

REcording studios are chock full of signal processing gear that uses SMPS. They don;t seem to have any trouble with it. I can think of such products that used SMPS at least 25 years ago.

They have a lot of troubles. Every month or more often somebody on gearslutz.com forum opens a topic about something to discover that all that problems are caused by interferences from power supplies and ground loops.

Why it happens, because not all devices they use have good well balanced ins/louts. The troublemaker number one in many studios is a computer notebook.

Speaking of power amps, as Nelson Pass said already, while from a standard linear transformers + rectifiers you may squeeze shortly enormous power, SMPS can you give only and only up to certain limit it was designed for. I made a prototype (Pyranha project) that was powered from both 120V (800 VA toroidal transformer) and 12V (1200VA inverter). Inverter could not keep up with peaks, coughing on a full power much more often than I expected.

[abraxalito]

Originally Posted by Wavebourn

Speaking of power amps, as Nelson Pass said already, while from a standard linear transformers + rectifiers you may squeeze shortly enormous power, SMPS can you give only and only up to certain limit it was designed for. I made a prototype (Pyranha project) that was powered from both 120V (800 VA toroidal transformer) and 12V (1200VA inverter). Inverter could not keep up with peaks, coughing on a full power much more often than I expected.

I'll guess that the inverter didn't have such large rail caps on the output as the toroidal PSU. SMPSs have current limits but the peak current is available all the time at the rated output voltage. Whereas trafo with rectifier has higher peak current but most of the time its output is much more saggy.