Can an audio circuit be powered by a switched-mode power supply?

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Betty19
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Can an audio circuit be powered by a switched-mode power supply?

Post by Betty19 » Tue Apr 25, 2017 5:17 am

Most audio circuits a powered with large, heavy transformers and a small ripple after smoothing. SMPS are smaller and more efficient. EMI can be shielded by a metal enclosure and the output filtered for noise suppression.

Especially where the power is going to be further regulated. Why aren't switched-mode power supplies used in audio circuits, eg. power amplifiers, and what improvements can be done to make a SMPS suit an audio circuit?
Many high band audio companies now use SMPS for various reasons, not all but mostly because of

(A) Weight of iron core/copper winding transformers
(B) Efficiency of coupling between windings {ie power loss}
(C) Actual cost of copper these days
Anyone who has ever worked with high power PA systems will know that the bigger the amplifier (600W to 1Kw and above now are common) are heavy and large in size to fit into your standard rack mount road cases.

Standard linear power supplies deliver anything from plus and minus rail voltages of 75 and over 'Fixed". Any 'power' from the supply that is not being used is "dropped" into the heatsink.

For example, a 1 kilowatt amplifier running at only 10% will lose more energy as heat than the same amplifier running at 90%.

Some few audio manufacturers have taken advantage of this and use input detecting circuitry to vary the output voltage of the power supply to only provide the necessary level of supply rails as required. Switching at between 4 and 10 times the audio frequency, (any HF artifacts can be easily filtered filtered out of the DC supply)

This fast switching varies the output voltage from, say, plus and minus 30V for low level signals, to plus and minus 90V (or above, depending on the FET/Transistor design). Because of the efficiency of SMPS, this greatly reduces the cost and weight of the amplifier as there are no longer any great lumps of steel and copper to lug around, but also no huge aluminum heatsinks to dissipate the great power losses, or those large fans required to shift enough air around them.

Unless poorly filtered, no "power supply" should impact on the audio quality of any amplifier be it linear or digital. A voltage is a voltage; flat and ripple free of any sort: after that it is the design of the amplifier that determines noise and distortion

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Enzo
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Re: Can an audio circuit be powered by a switched-mode power supply?

Post by Enzo » Tue Apr 25, 2017 8:23 am

SMPS are used in audio amps all the time, and have been for many years.

Commutating amps are not rare, those have two or more rails per side, and the higher voltage is switched in for peaks. But those higher supplies are continuously there. If you are proposing a supply that puts out a continuously variable 0-100v, that seems to me overly complex. You'd be basically building a power amp to power a power amp.

Why put it all on the poor SMPS? Why not just go to digital amplification in the first place?

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Roger Crimm
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Re: Can an audio circuit be powered by a switched-mode power supply?

Post by Roger Crimm » Tue Apr 25, 2017 8:59 am

I am pretty sure this was a spam bot. This exact post was copied and pasted on at least two other forums that I found. I have banned the bot and removed the spam link that was within the post.
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Enzo
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Re: Can an audio circuit be powered by a switched-mode power supply?

Post by Enzo » Tue Apr 25, 2017 6:34 pm

Oh well. Thanks.

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